Multiple Programs in WebGL doesn't work - javascript

I'm trying to use multiple shader programs in webgl but continue to get issues.
It seems that if i have a different number of vertex shader attributes in programs then i get nothing rendered with no errors. Is there some constraint that means that programs have to have the same number of attributes? Do i need to disable/enable attribute locations when changing programs?
It seems that just creating multiple programs causes the issue ( i dont even have to use the second shader, just the fact that it is created causes the issue).
To create the attributes i'm using the following snippet (works fine when number of attributes in all programs is the same):
for ( var i=0 ; i<vertexAttributes.length ; i++ )
{
shaderProgram[vertexAttributes[i].name] = gl.getAttribLocation(shaderProgram,vertexAttributes[i].name);
gl.enableVertexAttribArray(shaderProgram[vertexAttributes[i].name]);
}
Sorry for posting such a large chunk of code, but this best illustrates the issue. this is code from one of the learningwebgl.com tutorials, all that i have done is add a second pair of shaders ("shader2-fs" and "shader2-vs") and a new function called initShaders2. if initShaders2 is called in webGLStart() (as it is in the code) then nothing is drawn??? i'm baffled!
<script type="text/javascript" src="two_files/glMatrix-0.js"></script>
<script type="text/javascript" src="two_files/webgl-utils.js"></script>
<script id="shader-fs" type="x-shader/x-fragment">
precision mediump float;
varying vec4 vColor;
void main(void) {
gl_FragColor = vColor;
}
</script>
<script id="shader-vs" type="x-shader/x-vertex">
attribute vec3 aVertexPosition;
attribute vec4 aVertexColor;
uniform mat4 uMVMatrix;
uniform mat4 uPMatrix;
varying vec4 vColor;
void main(void) {
gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
vColor = aVertexColor;
}
</script>
<script id="shader2-fs" type="x-shader/x-fragment">
precision mediump float;
varying vec2 vTextureCoord;
varying vec3 vLightWeighting;
uniform sampler2D uSampler;
void main(void) {
vec4 textureColor = texture2D(uSampler, vec2(vTextureCoord.s, vTextureCoord.t));
gl_FragColor = vec4(textureColor.rgb * vLightWeighting, textureColor.a);
}
</script>
<script id="shader2-vs" type="x-shader/x-vertex">
attribute vec3 aVertexPosition;
attribute vec3 aVertexNormal;
attribute vec2 aTextureCoord;
uniform mat4 uMVMatrix;
uniform mat4 uPMatrix;
uniform mat3 uNMatrix;
uniform vec3 uAmbientColor;
uniform vec3 uLightingDirection;
uniform vec3 uDirectionalColor;
uniform bool uUseLighting;
varying vec2 vTextureCoord;
varying vec3 vLightWeighting;
void main(void) {
gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
vTextureCoord = aTextureCoord;
if (!uUseLighting) {
vLightWeighting = vec3(1.0, 1.0, 1.0);
} else {
vec3 transformedNormal = uNMatrix * aVertexNormal;
float directionalLightWeighting = max(dot(transformedNormal, uLightingDirection), 0.0);
vLightWeighting = uAmbientColor + uDirectionalColor * directionalLightWeighting;
}
}
</script>
<script type="text/javascript">
var gl;
function initGL(canvas) {
try {
gl = canvas.getContext("experimental-webgl");
gl.viewportWidth = canvas.width;
gl.viewportHeight = canvas.height;
} catch (e) {
}
if (!gl) {
alert("Could not initialise WebGL, sorry :-(");
}
}
function getShader(gl, id) {
var shaderScript = document.getElementById(id);
if (!shaderScript) {
return null;
}
var str = "";
var k = shaderScript.firstChild;
while (k) {
if (k.nodeType == 3) {
str += k.textContent;
}
k = k.nextSibling;
}
var shader;
if (shaderScript.type == "x-shader/x-fragment") {
shader = gl.createShader(gl.FRAGMENT_SHADER);
} else if (shaderScript.type == "x-shader/x-vertex") {
shader = gl.createShader(gl.VERTEX_SHADER);
} else {
return null;
}
gl.shaderSource(shader, str);
gl.compileShader(shader);
if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
alert(gl.getShaderInfoLog(shader));
return null;
}
return shader;
}
var shaderProgram;
function initShaders() {
var fragmentShader = getShader(gl, "shader-fs");
var vertexShader = getShader(gl, "shader-vs");
shaderProgram = gl.createProgram();
gl.attachShader(shaderProgram, vertexShader);
gl.attachShader(shaderProgram, fragmentShader);
gl.linkProgram(shaderProgram);
if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
alert("Could not initialise shaders");
}
gl.useProgram(shaderProgram);
shaderProgram.vertexPositionAttribute = gl.getAttribLocation(shaderProgram, "aVertexPosition");
gl.enableVertexAttribArray(shaderProgram.vertexPositionAttribute);
shaderProgram.vertexColorAttribute = gl.getAttribLocation(shaderProgram, "aVertexColor");
gl.enableVertexAttribArray(shaderProgram.vertexColorAttribute);
shaderProgram.pMatrixUniform = gl.getUniformLocation(shaderProgram, "uPMatrix");
shaderProgram.mvMatrixUniform = gl.getUniformLocation(shaderProgram, "uMVMatrix");
}
var shaderProgram2;
function initShaders2() {
var fragmentShader = getShader(gl, "shader2-fs");
var vertexShader = getShader(gl, "shader2-vs");
shaderProgram2 = gl.createProgram();
gl.attachShader(shaderProgram2, vertexShader);
gl.attachShader(shaderProgram2, fragmentShader);
gl.linkProgram(shaderProgram2);
if (!gl.getProgramParameter(shaderProgram2, gl.LINK_STATUS)) {
alert("Could not initialise shaders");
}
gl.useProgram(shaderProgram2);
shaderProgram2.vertexPositionAttribute = gl.getAttribLocation(shaderProgram2, "aVertexPosition");
gl.enableVertexAttribArray(shaderProgram2.vertexPositionAttribute);
shaderProgram2.vertexNormalAttribute = gl.getAttribLocation(shaderProgram2, "aVertexNormal");
gl.enableVertexAttribArray(shaderProgram2.vertexNormalAttribute);
shaderProgram2.textureCoordAttribute = gl.getAttribLocation(shaderProgram2, "aTextureCoord");
gl.enableVertexAttribArray(shaderProgram2.textureCoordAttribute);
shaderProgram2.pMatrixUniform = gl.getUniformLocation(shaderProgram2, "uPMatrix");
shaderProgram2.mvMatrixUniform = gl.getUniformLocation(shaderProgram2, "uMVMatrix");
shaderProgram2.nMatrixUniform = gl.getUniformLocation(shaderProgram2, "uNMatrix");
shaderProgram2.samplerUniform = gl.getUniformLocation(shaderProgram2, "uSampler");
shaderProgram2.useLightingUniform = gl.getUniformLocation(shaderProgram2, "uUseLighting");
shaderProgram2.ambientColorUniform = gl.getUniformLocation(shaderProgram2, "uAmbientColor");
shaderProgram2.lightingDirectionUniform = gl.getUniformLocation(shaderProgram2, "uLightingDirection");
shaderProgram2.directionalColorUniform = gl.getUniformLocation(shaderProgram2, "uDirectionalColor");
}
var mvMatrix = mat4.create();
var mvMatrixStack = [];
var pMatrix = mat4.create();
function mvPushMatrix() {
var copy = mat4.create();
mat4.set(mvMatrix, copy);
mvMatrixStack.push(copy);
}
function mvPopMatrix() {
if (mvMatrixStack.length == 0) {
throw "Invalid popMatrix!";
}
mvMatrix = mvMatrixStack.pop();
}
function setMatrixUniforms() {
gl.uniformMatrix4fv(shaderProgram.pMatrixUniform, false, pMatrix);
gl.uniformMatrix4fv(shaderProgram.mvMatrixUniform, false, mvMatrix);
}
function degToRad(degrees) {
return degrees * Math.PI / 180;
}
var pyramidVertexPositionBuffer;
var pyramidVertexColorBuffer;
var cubeVertexPositionBuffer;
var cubeVertexColorBuffer;
var cubeVertexIndexBuffer;
function initBuffers() {
pyramidVertexPositionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, pyramidVertexPositionBuffer);
var vertices = [
// Front face
0.0, 1.0, 0.0,
-1.0, -1.0, 1.0,
1.0, -1.0, 1.0,
// Right face
0.0, 1.0, 0.0,
1.0, -1.0, 1.0,
1.0, -1.0, -1.0,
// Back face
0.0, 1.0, 0.0,
1.0, -1.0, -1.0,
-1.0, -1.0, -1.0,
// Left face
0.0, 1.0, 0.0,
-1.0, -1.0, -1.0,
-1.0, -1.0, 1.0
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
pyramidVertexPositionBuffer.itemSize = 3;
pyramidVertexPositionBuffer.numItems = 12;
pyramidVertexColorBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, pyramidVertexColorBuffer);
var colors = [
// Front face
1.0, 0.0, 0.0, 1.0,
0.0, 1.0, 0.0, 1.0,
0.0, 0.0, 1.0, 1.0,
// Right face
1.0, 0.0, 0.0, 1.0,
0.0, 0.0, 1.0, 1.0,
0.0, 1.0, 0.0, 1.0,
// Back face
1.0, 0.0, 0.0, 1.0,
0.0, 1.0, 0.0, 1.0,
0.0, 0.0, 1.0, 1.0,
// Left face
1.0, 0.0, 0.0, 1.0,
0.0, 0.0, 1.0, 1.0,
0.0, 1.0, 0.0, 1.0
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW);
pyramidVertexColorBuffer.itemSize = 4;
pyramidVertexColorBuffer.numItems = 12;
cubeVertexPositionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
vertices = [
// Front face
-1.0, -1.0, 1.0,
1.0, -1.0, 1.0,
1.0, 1.0, 1.0,
-1.0, 1.0, 1.0,
// Back face
-1.0, -1.0, -1.0,
-1.0, 1.0, -1.0,
1.0, 1.0, -1.0,
1.0, -1.0, -1.0,
// Top face
-1.0, 1.0, -1.0,
-1.0, 1.0, 1.0,
1.0, 1.0, 1.0,
1.0, 1.0, -1.0,
// Bottom face
-1.0, -1.0, -1.0,
1.0, -1.0, -1.0,
1.0, -1.0, 1.0,
-1.0, -1.0, 1.0,
// Right face
1.0, -1.0, -1.0,
1.0, 1.0, -1.0,
1.0, 1.0, 1.0,
1.0, -1.0, 1.0,
// Left face
-1.0, -1.0, -1.0,
-1.0, -1.0, 1.0,
-1.0, 1.0, 1.0,
-1.0, 1.0, -1.0
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
cubeVertexPositionBuffer.itemSize = 3;
cubeVertexPositionBuffer.numItems = 24;
cubeVertexColorBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexColorBuffer);
colors = [
[1.0, 0.0, 0.0, 1.0], // Front face
[1.0, 1.0, 0.0, 1.0], // Back face
[0.0, 1.0, 0.0, 1.0], // Top face
[1.0, 0.5, 0.5, 1.0], // Bottom face
[1.0, 0.0, 1.0, 1.0], // Right face
[0.0, 0.0, 1.0, 1.0] // Left face
];
var unpackedColors = [];
for (var i in colors) {
var color = colors[i];
for (var j=0; j < 4; j++) {
unpackedColors = unpackedColors.concat(color);
}
}
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(unpackedColors), gl.STATIC_DRAW);
cubeVertexColorBuffer.itemSize = 4;
cubeVertexColorBuffer.numItems = 24;
cubeVertexIndexBuffer = gl.createBuffer();
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
var cubeVertexIndices = [
0, 1, 2, 0, 2, 3, // Front face
4, 5, 6, 4, 6, 7, // Back face
8, 9, 10, 8, 10, 11, // Top face
12, 13, 14, 12, 14, 15, // Bottom face
16, 17, 18, 16, 18, 19, // Right face
20, 21, 22, 20, 22, 23 // Left face
];
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(cubeVertexIndices), gl.STATIC_DRAW);
cubeVertexIndexBuffer.itemSize = 1;
cubeVertexIndexBuffer.numItems = 36;
}
var rPyramid = 0;
var rCube = 0;
function drawScene() {
gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
mat4.perspective(45, gl.viewportWidth / gl.viewportHeight, 0.1, 100.0, pMatrix);
mat4.identity(mvMatrix);
mat4.translate(mvMatrix, [-1.5, 0.0, -8.0]);
mvPushMatrix();
mat4.rotate(mvMatrix, degToRad(rPyramid), [0, 1, 0]);
gl.bindBuffer(gl.ARRAY_BUFFER, pyramidVertexPositionBuffer);
gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, pyramidVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ARRAY_BUFFER, pyramidVertexColorBuffer);
gl.vertexAttribPointer(shaderProgram.vertexColorAttribute, pyramidVertexColorBuffer.itemSize, gl.FLOAT, false, 0, 0);
setMatrixUniforms();
gl.drawArrays(gl.TRIANGLES, 0, pyramidVertexPositionBuffer.numItems);
mvPopMatrix();
mat4.translate(mvMatrix, [3.0, 0.0, 0.0]);
mvPushMatrix();
mat4.rotate(mvMatrix, degToRad(rCube), [1, 1, 1]);
gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, cubeVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexColorBuffer);
gl.vertexAttribPointer(shaderProgram.vertexColorAttribute, cubeVertexColorBuffer.itemSize, gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
setMatrixUniforms();
gl.drawElements(gl.TRIANGLES, cubeVertexIndexBuffer.numItems, gl.UNSIGNED_SHORT, 0);
mvPopMatrix();
}
var lastTime = 0;
function animate() {
var timeNow = new Date().getTime();
if (lastTime != 0) {
var elapsed = timeNow - lastTime;
rPyramid += (90 * elapsed) / 1000.0;
rCube -= (75 * elapsed) / 1000.0;
}
lastTime = timeNow;
}
function tick() {
requestAnimFrame(tick);
drawScene();
animate();
}
function webGLStart() {
var canvas = document.getElementById("lesson04-canvas");
initGL(canvas);
initShaders2(); // !!!!!!!!!!!!!!!!!!!!!!!!!
initShaders();
initBuffers();
gl.clearColor(0.0, 0.0, 0.0, 1.0);
gl.enable(gl.DEPTH_TEST);
tick();
}
</script>
</head>
<body onload="webGLStart();">
<< Back to Lesson 4<br>
<canvas id="lesson04-canvas" style="border: none;" width="500" height="500"></canvas>
<br>
<< Back to Lesson 4<br>
</body></html>

You'll probably need to give us a little bit more information, but to get you started here's a quick checklist. Any time you change programs, you'll want to:
Enable the appropriate vertex attribute arrays
Bind the vertex attribute pointers, even if they were already bound to the right buffers
Bind any uniforms needed, like texture samplers.
Basically, you want to treat every time you change programs as if it's the first time you're setting up a draw call.

Related

Range Slider for camera in WebGL

I'm trying to get a range slider to change the far plane and the angle of the camera in Webgl but I can't. How do I do in order for my code to read the value from the slider and then change the value in the perspective of the camera?
// Application info.
var app = app || {};
function initGL() {
var gl = app.gl;
gl.enable(gl.DEPTH_TEST);
gl.depthFunc(gl.LEQUAL);
gl.viewport(0, 0, app.can.width, app.can.height);
gl.clearColor(0., 0., 0., 1.0);
gl.clear(app.gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
var vs = createShaderFromElement(app.gl, "vs");
var fs = createShaderFromElement(app.gl, "fs");
app.progObject = buildProgram(app.gl, vs, fs);
gl.useProgram(app.progObject);
}
function initScene() {
var gl = app.gl;
// Creer le buffer de geometrie (vertex)
//
var positions = [
// Front face
-1.0, -1.0, 1.0,
1.0, -1.0, 1.0,
1.0, 1.0, 1.0,
1.0, 1.0, 1.0, -1.0, 1.0, 1.0, -1.0, -1.0, 1.0,
// Back face
-1.0, -1.0, -1.0, -1.0, 1.0, -1.0,
1.0, 1.0, -1.0,
1.0, 1.0, -1.0,
1.0, -1.0, -1.0, -1.0, -1.0, -1.0,
// Top face
-1.0, 1.0, -1.0, -1.0, 1.0, 1.0,
1.0, 1.0, 1.0,
1.0, 1.0, 1.0,
1.0, 1.0, -1.0, -1.0, 1.0, -1.0,
// Bottom face
-1.0, -1.0, -1.0,
1.0, -1.0, -1.0,
1.0, -1.0, 1.0,
1.0, -1.0, 1.0, -1.0, -1.0, 1.0, -1.0, -1.0, -1.0,
// Right face
1.0, -1.0, -1.0,
1.0, 1.0, -1.0,
1.0, 1.0, 1.0,
1.0, 1.0, 1.0,
1.0, -1.0, 1.0,
1.0, -1.0, -1.0,
// Left face
-1.0, -1.0, -1.0, -1.0, -1.0, 1.0, -1.0, 1.0, 1.0, -1.0, 1.0, 1.0, -1.0, 1.0, -1.0, -1.0, -1.0, -1.0
];
app.nPoints = positions.length / 3;
var colors = [
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0,
0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0,
0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1,
1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0,
1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1
];
var loc, buffer;
// Create and copy position buffer.
loc = gl.getAttribLocation(app.progObject, "pos");
buffer = gl.createBuffer();
gl.enableVertexAttribArray(loc);
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.vertexAttribPointer(loc, 3, gl.FLOAT, false /*no normalization*/, 0 /*stride*/, 0 /*offset*/);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(positions), gl.STATIC_DRAW);
// Create and copy color buffer.
loc = gl.getAttribLocation(app.progObject, "color");
buffer = gl.createBuffer();
gl.enableVertexAttribArray(loc);
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.vertexAttribPointer(loc, 3, gl.FLOAT, false /*no normalization*/, 0 /*stride*/, 0 /*offset*/);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW);
// Look for uniforms.
app.pmLocation = gl.getUniformLocation(app.progObject, "projMatrix");
app.mmLocation = gl.getUniformLocation(app.progObject, "modelMatrix");
app.vmLocation = gl.getUniformLocation(app.progObject, "viewMatrix");
var mat4 = glMatrix.mat4;
app.projMatrix = mat4.create();
app.modelMatrix = mat4.create();
app.viewMatrix = mat4.create();
app.pcam = mat4.create();
app.mvpMatrix = mat4.create();
var near = 0.1;
mat4.perspective(app.projMatrix, Math.PI / 4.0 /*45 degrees*/, 1, 0.1, farChanged());
mat4.lookAt(app.viewMatrix, [ 15, 0, -10], [-5, 0, 0], [0, 1, 0]);
}
function animate(time) {
var gl = app.gl;
var mat4 = glMatrix.mat4;
// converts to seconds.
var seconds = time * 1E-3;
var dtime = time - app.oldTime;
var mm1 = mat4.create();
mat4.translate(mm1, app.modelMatrix, [2, 0, 0]);
var angle = time * 0.001;
mat4.rotateY(mm1, mm1, angle);
app.oldTime = time;
gl.clear(app.gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
gl.uniformMatrix4fv(app.pmLocation, false, app.projMatrix);
gl.uniformMatrix4fv(app.mmLocation, false, mm1);
gl.uniformMatrix4fv(app.vmLocation, false, app.viewMatrix);
gl.drawArrays(gl.TRIANGLES, 0, app.nPoints);
// Pour dessiner autre cube, calculer autre model matrix
// et redessiner ... gl.drawArrays(gl.TRIANGLES, 0, app.nPoints);
var mm2 = mat4.create();
mat4.translate(mm2, app.modelMatrix, [-2, 0, 0]);
mat4.rotateY(mm2, mm2, angle)
gl.uniformMatrix4fv(app.pmLocation, false, app.projMatrix);
gl.uniformMatrix4fv(app.mmLocation, false, mm2);
gl.uniformMatrix4fv(app.vmLocation, false, app.viewMatrix);
gl.drawArrays(gl.TRIANGLES, 0, app.nPoints);
//for the camera
var moveInAndOut = 0.1 * Math.cos(angle);
var moveLeftAndRight = 0.1 * Math.sin(angle);
app.pcam = ([moveInAndOut, 0, moveLeftAndRight]);
// app.viewMatrix = lookAt(app.pcam, [0, 0, 0], [0, 1, 0]);
// mat4.lookAt(app.viewMatrix, app.pcam , [0, 0, 0], [0, 1, 0]);
mat4.translate(app.viewMatrix, app.viewMatrix, app.pcam);
mat4.rotateY(app.viewMatrix, app.viewMatrix, 0.05);
window.requestAnimationFrame(animate);
}
function fovChanged(id, value) {
console.log("FOV Angle: ", value);
var label = document.getElementById('output-fov');
label.innerHTML = value;
}
function farChanged(id, value) {
console.log("Far Plane: ", value);
var label2 = document.getElementById('output-far');
label2.innerHTML = value;
}
function init() {
[app.can, app.gl] = getContextGL('can');
if (app.can == null || app.gl == null) {
alert("Can't init canvas or context");
return;
}
app.can.width = app.can.height * (app.can.clientWidth / app.can.clientHeight);
var rect = app.can.getBoundingClientRect();
app.scaleX = app.can.width / rect.width;
app.scaleY = app.can.height / rect.height;
initGL();
initScene();
app.oldTime = 0;
animate(0);
}
init();
// -----
function getContextGL(id) {
const can = document.getElementById(id);
const gl = can.getContext('webgl');
return [can, gl];
}
function createShaderFromElement(gl, id) {
const e = document.getElementById(id);
const s = gl.createShader(e.type.indexOf('vertex') >= 0 ? gl.VERTEX_SHADER : gl.FRAGMENT_SHADER);
gl.shaderSource(s, e.text);
gl.compileShader(s);
return s;
}
function buildProgram(gl, vs, fs) {
const p = gl.createProgram();
gl.attachShader(p, vs);
gl.attachShader(p, fs);
gl.linkProgram(p);
return p;
}
div
{
}
#main-div
{
display:inline-block;
}
#viewport, #manager
{
float: left;
margin: auto;
}
.color
{
width:100px;
height:50px;
}
.blue{
background:#0f0;
}
#viewport
{
width: 600px;
height:700px;
}
#can
{
width: 600px;
height: 500px;
border:1px solid orange;
}
#manager
{
width: 200px;
height:300px;
padding: 0 0 0 5px;
}
#obj-list
{
width: 200px;
}
<!DOCTYPE html>
<html>
<head>
<title>Cube Transform</title>
<link rel="stylesheet" type="text/css" href="style.css">
<script src="transforms.js"></script>
<script src="utils.js"></script>
<script src="gl-matrix-min.js"></script>
<script id="vs" type="x-shader/x-vertex">
precision mediump float;
uniform mat4 projMatrix;
uniform mat4 viewMatrix;
uniform mat4 modelMatrix;
attribute vec3 pos;
attribute vec3 color;
varying vec3 fColor;
void main()
{
fColor = color;
vec4 pt = vec4(pos, 1.0);
gl_Position = projMatrix * viewMatrix * modelMatrix * pt;
}
</script>
<script id="fs" type="x-shader/x-fragment">
precision mediump float;
varying vec3 fColor;
void main()
{
gl_FragColor = vec4(fColor,1);
}
</script>
</head>
<body onload="init();">
<div id="main-div">
<div id="viewport">
<canvas id="can" >Your browser doesn't seem to support canvas!</canvas>
<div class="slider">
<span class="slider-label">FOV cam</span>
<input id="fov" class="slider-input" type="range" min="20" max="90" step="1" value="0" onClick="fovChanged(this.id, this.value)" />
<span id="output-fov" class="slider-value">20</span>
</div>
<div class="slider">
<span class="slider-label">Far Plane</span>
<input id="far" class="slider-input" type="range" min="5" max="30" step="0.1" value="0" onClick="farChanged(this.id, this.value)" />
<span id="output-far" class="slider-value">5</span>
</div>
</div>
</div>
</body>
</html>
My code contains multiple files so here's the link to the full code:
https://wetransfer.com/downloads/f05fa22faa0e0803a0b6fa13348d7d9520200920195230/52fc67
The js code is in transforms.js.
Thank you!
This line
mat4.perspective(app.projMatrix, Math.PI / 4.0 /*45 degrees*/, 1, 0.1, farChanged());
makes no sense. farChanged does not return anything. It just sets the label's innerHTML
You need to update the project matrix when the event gets called
function farChanged(id, value) {
var label2 = document.getElementById('output-far');
label2.innerHTML = value;
glMatrix.mat4.perspective(app.projMatrix, Math.PI / 4.0 /*45 degrees*/ , 1, 0.1, parseFloat(value));
}
// Application info.
var app = app || {};
function initGL() {
var gl = app.gl;
gl.enable(gl.DEPTH_TEST);
gl.depthFunc(gl.LEQUAL);
gl.viewport(0, 0, app.can.width, app.can.height);
gl.clearColor(0., 0., 0., 1.0);
gl.clear(app.gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
var vs = createShaderFromElement(app.gl, "vs");
var fs = createShaderFromElement(app.gl, "fs");
app.progObject = buildProgram(app.gl, vs, fs);
gl.useProgram(app.progObject);
}
function initScene() {
var gl = app.gl;
// Creer le buffer de geometrie (vertex)
//
var positions = [
// Front face
-1.0, -1.0, 1.0,
1.0, -1.0, 1.0,
1.0, 1.0, 1.0,
1.0, 1.0, 1.0, -1.0, 1.0, 1.0, -1.0, -1.0, 1.0,
// Back face
-1.0, -1.0, -1.0, -1.0, 1.0, -1.0,
1.0, 1.0, -1.0,
1.0, 1.0, -1.0,
1.0, -1.0, -1.0, -1.0, -1.0, -1.0,
// Top face
-1.0, 1.0, -1.0, -1.0, 1.0, 1.0,
1.0, 1.0, 1.0,
1.0, 1.0, 1.0,
1.0, 1.0, -1.0, -1.0, 1.0, -1.0,
// Bottom face
-1.0, -1.0, -1.0,
1.0, -1.0, -1.0,
1.0, -1.0, 1.0,
1.0, -1.0, 1.0, -1.0, -1.0, 1.0, -1.0, -1.0, -1.0,
// Right face
1.0, -1.0, -1.0,
1.0, 1.0, -1.0,
1.0, 1.0, 1.0,
1.0, 1.0, 1.0,
1.0, -1.0, 1.0,
1.0, -1.0, -1.0,
// Left face
-1.0, -1.0, -1.0, -1.0, -1.0, 1.0, -1.0, 1.0, 1.0, -1.0, 1.0, 1.0, -1.0, 1.0, -1.0, -1.0, -1.0, -1.0
];
app.nPoints = positions.length / 3;
var colors = [
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0,
0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0,
0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1,
1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0,
1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1
];
var loc, buffer;
// Create and copy position buffer.
loc = gl.getAttribLocation(app.progObject, "pos");
buffer = gl.createBuffer();
gl.enableVertexAttribArray(loc);
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.vertexAttribPointer(loc, 3, gl.FLOAT, false /*no normalization*/ , 0 /*stride*/ , 0 /*offset*/ );
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(positions), gl.STATIC_DRAW);
// Create and copy color buffer.
loc = gl.getAttribLocation(app.progObject, "color");
buffer = gl.createBuffer();
gl.enableVertexAttribArray(loc);
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.vertexAttribPointer(loc, 3, gl.FLOAT, false /*no normalization*/ , 0 /*stride*/ , 0 /*offset*/ );
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW);
// Look for uniforms.
app.pmLocation = gl.getUniformLocation(app.progObject, "projMatrix");
app.mmLocation = gl.getUniformLocation(app.progObject, "modelMatrix");
app.vmLocation = gl.getUniformLocation(app.progObject, "viewMatrix");
var mat4 = glMatrix.mat4;
app.projMatrix = mat4.create();
app.modelMatrix = mat4.create();
app.viewMatrix = mat4.create();
app.pcam = mat4.create();
app.mvpMatrix = mat4.create();
var near = 0.1;
mat4.perspective(app.projMatrix, Math.PI / 4.0 /*45 degrees*/ , 1, 0.1, 10);
mat4.lookAt(app.viewMatrix, [15, 0, -10], [-5, 0, 0], [0, 1, 0]);
}
function animate(time) {
var gl = app.gl;
var mat4 = glMatrix.mat4;
// converts to seconds.
var seconds = time * 1E-3;
var dtime = time - app.oldTime;
var mm1 = mat4.create();
mat4.translate(mm1, app.modelMatrix, [2, 0, 0]);
var angle = time * 0.001;
mat4.rotateY(mm1, mm1, angle);
app.oldTime = time;
gl.clear(app.gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
gl.uniformMatrix4fv(app.pmLocation, false, app.projMatrix);
gl.uniformMatrix4fv(app.mmLocation, false, mm1);
gl.uniformMatrix4fv(app.vmLocation, false, app.viewMatrix);
gl.drawArrays(gl.TRIANGLES, 0, app.nPoints);
// Pour dessiner autre cube, calculer autre model matrix
// et redessiner ... gl.drawArrays(gl.TRIANGLES, 0, app.nPoints);
var mm2 = mat4.create();
mat4.translate(mm2, app.modelMatrix, [-2, 0, 0]);
mat4.rotateY(mm2, mm2, angle)
gl.uniformMatrix4fv(app.pmLocation, false, app.projMatrix);
gl.uniformMatrix4fv(app.mmLocation, false, mm2);
gl.uniformMatrix4fv(app.vmLocation, false, app.viewMatrix);
gl.drawArrays(gl.TRIANGLES, 0, app.nPoints);
//for the camera
var moveInAndOut = 0.1 * Math.cos(angle);
var moveLeftAndRight = 0.1 * Math.sin(angle);
app.pcam = ([moveInAndOut, 0, moveLeftAndRight]);
// app.viewMatrix = lookAt(app.pcam, [0, 0, 0], [0, 1, 0]);
// mat4.lookAt(app.viewMatrix, app.pcam , [0, 0, 0], [0, 1, 0]);
mat4.translate(app.viewMatrix, app.viewMatrix, app.pcam);
mat4.rotateY(app.viewMatrix, app.viewMatrix, 0.05);
window.requestAnimationFrame(animate);
}
function fovChanged(id, value) {
console.log("FOV Angle: ", value);
var label = document.getElementById('output-fov');
label.innerHTML = value;
}
function farChanged(id, value) {
//console.log("Far Plane: ", value);
var label2 = document.getElementById('output-far');
label2.innerHTML = value;
glMatrix.mat4.perspective(app.projMatrix, Math.PI / 4.0 /*45 degrees*/ , 1, 0.1, parseFloat(value));
}
function init() {
[app.can, app.gl] = getContextGL('can');
if (app.can == null || app.gl == null) {
alert("Can't init canvas or context");
return;
}
app.can.width = app.can.height * (app.can.clientWidth / app.can.clientHeight);
var rect = app.can.getBoundingClientRect();
app.scaleX = app.can.width / rect.width;
app.scaleY = app.can.height / rect.height;
initGL();
initScene();
app.oldTime = 0;
animate(0);
}
init();
// -----
function getContextGL(id) {
const can = document.getElementById(id);
const gl = can.getContext('webgl');
return [can, gl];
}
function createShaderFromElement(gl, id) {
const e = document.getElementById(id);
const s = gl.createShader(e.type.indexOf('vertex') >= 0 ? gl.VERTEX_SHADER : gl.FRAGMENT_SHADER);
gl.shaderSource(s, e.text);
gl.compileShader(s);
return s;
}
function buildProgram(gl, vs, fs) {
const p = gl.createProgram();
gl.attachShader(p, vs);
gl.attachShader(p, fs);
gl.linkProgram(p);
return p;
}
div {}
#main-div {
display: inline-block;
}
#viewport,
#manager {
float: left;
margin: auto;
}
.color {
width: 100px;
height: 50px;
}
.blue {
background: #0f0;
}
#viewport {
width: 600px;
height: 700px;
}
#can {
width: 600px;
height: 500px;
border: 1px solid orange;
}
#manager {
width: 200px;
height: 300px;
padding: 0 0 0 5px;
}
#obj-list {
width: 200px;
}
<div id="main-div">
<div id="viewport">
<canvas id="can">Your browser doesn't seem to support canvas!</canvas>
<div class="slider">
<span class="slider-label">FOV cam</span>
<input id="fov" class="slider-input" type="range" min="20" max="90" step="1" value="0" onClick="fovChanged(this.id, this.value)" />
<span id="output-fov" class="slider-value">20</span>
</div>
<div class="slider">
<span class="slider-label">Far Plane</span>
<input id="far" class="slider-input" type="range" min="5" max="30" step="0.1" value="0" onClick="farChanged(this.id, this.value)" />
<span id="output-far" class="slider-value">5</span>
</div>
</div>
</div>
<script id="vs" type="x-shader/x-vertex">
precision mediump float;
uniform mat4 projMatrix;
uniform mat4 viewMatrix;
uniform mat4 modelMatrix;
attribute vec3 pos;
attribute vec3 color;
varying vec3 fColor;
void main()
{
fColor = color;
vec4 pt = vec4(pos, 1.0);
gl_Position = projMatrix * viewMatrix * modelMatrix * pt;
}
</script>
<script id="fs" type="x-shader/x-fragment">
precision mediump float;
varying vec3 fColor;
void main()
{
gl_FragColor = vec4(fColor,1);
}
</script>
<script src="https://cdn.jsdelivr.net/npm/gl-matrix#3.3.0/gl-matrix-min.js"></script>
Some other things.
Don't use body onload: https://stackoverflow.com/a/48256189/128511
Use addEventListener(eventName, function) instead of onClick="string"
Use the input event instead of the click event
don't set innerHTML, instead set textContent
Learn to use the snippets so they work (see the snippet above). In particular you didn't need <html>, <head>, links to <scripts> that don't exist and you needed to link to a cdn for glMatrix.

Rotating Triangle in WebGL

I am trying to render a 3D rotating triangle, I have made all the necessary changes but my triangle is way out of shape(doesn't look like a triangle). Do you guys know what I am missing here?
edit: I have attached the output, and yes I have tried playing with the vertices and it doesn't do much(as in it doesn't form a triangle)
var canvas;
var gl;
var NumVertices = 12;
var points = [];
var colors = [];
var xAxis = 0;
var yAxis = 1;
var zAxis = 2;
var axis = 0;
var theta = [ 0, 0, 0 ];
var thetaLoc;
var vertices = [
vec3(0.5, -0.2722, 0.2886),
vec3(0.0, -0.2722, -0.5773),
vec3(-0.5, -0.2722, 0.2886),
vec3(0.5, -0.5443, 0.0)
]
var vertexColors = [
[ 0.0, 0.0, 0.0, 1.0 ], // black
[ 1.0, 0.0, 0.0, 1.0 ], // red
[ 1.0, 1.0, 0.0, 1.0 ], // yellow
[ 0.0, 1.0, 0.0, 1.0 ] // green
];
window.onload = function init()
{
canvas = document.getElementById( "gl-canvas" );
gl = WebGLUtils.setupWebGL( canvas );
if ( !gl ) { alert( "WebGL isn't available" ); }
colorCube(); //change this name to pyramid
gl.viewport( 0, 0, canvas.width, canvas.height );
gl.clearColor( 1.0, 1.0, 1.0, 1.0 );
gl.enable(gl.DEPTH_TEST);
var program = initShaders( gl, "vertex-shader", "fragment-shader" );
gl.useProgram( program );
var cBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, cBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(colors), gl.STATIC_DRAW );
var vColor = gl.getAttribLocation( program, "vColor" );
gl.vertexAttribPointer( vColor, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vColor );
var vBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, vBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(points), gl.STATIC_DRAW );
var vPosition = gl.getAttribLocation( program, "vPosition" );
gl.vertexAttribPointer( vPosition, 3, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vPosition );
thetaLoc = gl.getUniformLocation(program, "theta");
document.getElementById( "xButton" ).onclick = function () {
axis = xAxis;
};
document.getElementById( "yButton" ).onclick = function () {
axis = yAxis;
};
document.getElementById( "zButton" ).onclick = function () {
axis = zAxis;
};
render();
}
function colorCube()
{
quad( 0, 1, 2 );
quad( 3, 1, 0 );
quad( 0, 1, 2 );
quad( 0, 2, 3 );
}
function quad(a, b, c)
{
var indices = [ a, b, c];
for ( var i = 0; i < indices.length; ++i ) {
points.push( vertices[indices[i]] );
colors.push(vertexColors[a]);
}
}
function render()
{
gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
theta[axis] += 2.0;
gl.uniform3fv(thetaLoc, theta);
gl.drawArrays( gl.TRIANGLES, 0, NumVertices );
requestAnimFrame( render );
}
<canvas id="gl-canvas" width="512"" height="512">
Oops ... your browser doesn't support the HTML5 canvas element
</canvas>
<br/>
<button id= "xButton">Rotate X</button>
<button id= "yButton">Rotate Y</button>
<button id= "zButton">Rotate Z</button>
<script id="vertex-shader" type="x-shader/x-vertex">
attribute vec4 vPosition;
attribute vec4 vColor;
varying vec4 fColor;
uniform vec3 theta;
void main()
{
// Compute the sines and cosines of theta for each of
// the three axes in one computation.
vec3 angles = radians( theta );
vec3 c = cos( angles );
vec3 s = sin( angles );
// Remeber: thse matrices are column-major
mat4 rx = mat4( 1.0, 0.0, 0.0, 0.0,
0.0, c.x, s.x, 0.0,
0.0, -s.x, c.x, 0.0,
0.0, 0.0, 0.0, 1.0 );
mat4 ry = mat4( c.y, 0.0, -s.y, 0.0,
0.0, 1.0, 0.0, 0.0,
s.y, 0.0, c.y, 0.0,
0.0, 0.0, 0.0, 1.0 );
mat4 rz = mat4( c.z, -s.z, 0.0, 0.0,
s.z, c.z, 0.0, 0.0,
0.0, 0.0, 1.0, 0.0,
0.0, 0.0, 0.0, 1.0 );
fColor = vColor;
gl_Position = rz * ry * rx * vPosition;
}
</script>
<script id="fragment-shader" type="x-shader/x-fragment">
precision mediump float;
varying vec4 fColor;
void
main()
{
gl_FragColor = fColor;
}
</script>
<script src="https://esangel.github.io/WebGL/Common/webgl-utils.js"></script>
<script src="https://esangel.github.io/WebGL/Common/initShaders.js"></script>
<script src="https://esangel.github.io/WebGL/Common/MV.js"></script>
--------------------------------Output---------------------------
Here is the picture of my output, which rotates on all the axis but it doesn't have the shape of a 3d Triangle
I think you just have bad indices in colorCube
I change them to this
function colorCube()
{
quad( 0, 1, 2 ); // bottom
quad( 1, 0, 3 ); // side0
quad( 1, 2, 3 ); // side1
quad( 2, 0, 3 ); // side3
}
and it seemed to work.
I also changed the way it picks colors for the faces so it just makes each triangle the next color.
function quad(a, b, c)
{
var indices = [ a, b, c];
var ndx = points.length % vertexColors.length;
for ( var i = 0; i < indices.length; ++i ) {
points.push( vertices[indices[i]] );
colors.push(vertexColors[ndx]);
}
}
Seems to work.
var canvas;
var gl;
var NumVertices = 12;
var points = [];
var colors = [];
var xAxis = 0;
var yAxis = 1;
var zAxis = 2;
var axis = 0;
var theta = [ 0, 0, 0 ];
var thetaLoc;
var vertices = [
vec3(0.5, -0.2722, 0.2886),
vec3(0.0, -0.2722, -0.5773),
vec3(-0.5, -0.2722, 0.2886),
vec3(0.5, -0.5443, 0.0)
]
var vertexColors = [
[ 0.0, 0.0, 0.0, 1.0 ], // black
[ 1.0, 0.0, 0.0, 1.0 ], // red
[ 1.0, 1.0, 0.0, 1.0 ], // yellow
[ 0.0, 1.0, 0.0, 1.0 ] // green
];
window.onload = function init()
{
canvas = document.getElementById( "gl-canvas" );
gl = WebGLUtils.setupWebGL( canvas );
if ( !gl ) { alert( "WebGL isn't available" ); }
colorCube(); //change this name to pyramid
gl.viewport( 0, 0, canvas.width, canvas.height );
gl.clearColor( 1.0, 1.0, 1.0, 1.0 );
gl.enable(gl.DEPTH_TEST);
var program = initShaders( gl, "vertex-shader", "fragment-shader" );
gl.useProgram( program );
var cBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, cBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(colors), gl.STATIC_DRAW );
var vColor = gl.getAttribLocation( program, "vColor" );
gl.vertexAttribPointer( vColor, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vColor );
var vBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, vBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(points), gl.STATIC_DRAW );
var vPosition = gl.getAttribLocation( program, "vPosition" );
gl.vertexAttribPointer( vPosition, 3, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vPosition );
thetaLoc = gl.getUniformLocation(program, "theta");
document.getElementById( "xButton" ).onclick = function () {
axis = xAxis;
};
document.getElementById( "yButton" ).onclick = function () {
axis = yAxis;
};
document.getElementById( "zButton" ).onclick = function () {
axis = zAxis;
};
render();
}
function colorCube()
{
quad( 0, 1, 2 ); // bottom
quad( 1, 0, 3 ); // side0
quad( 1, 2, 3 ); // side1
quad( 2, 0, 3 ); // side3
}
function quad(a, b, c)
{
var indices = [ a, b, c];
var ndx = points.length % vertexColors.length;
for ( var i = 0; i < indices.length; ++i ) {
points.push( vertices[indices[i]] );
colors.push(vertexColors[ndx]);
}
}
function render()
{
gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
theta[axis] += 2.0;
gl.uniform3fv(thetaLoc, theta);
gl.drawArrays( gl.TRIANGLES, 0, NumVertices );
requestAnimFrame( render );
}
<canvas id="gl-canvas" width="512"" height="512">
Oops ... your browser doesn't support the HTML5 canvas element
</canvas>
<br/>
<button id= "xButton">Rotate X</button>
<button id= "yButton">Rotate Y</button>
<button id= "zButton">Rotate Z</button>
<script id="vertex-shader" type="x-shader/x-vertex">
attribute vec4 vPosition;
attribute vec4 vColor;
varying vec4 fColor;
uniform vec3 theta;
void main()
{
// Compute the sines and cosines of theta for each of
// the three axes in one computation.
vec3 angles = radians( theta );
vec3 c = cos( angles );
vec3 s = sin( angles );
// Remeber: thse matrices are column-major
mat4 rx = mat4( 1.0, 0.0, 0.0, 0.0,
0.0, c.x, s.x, 0.0,
0.0, -s.x, c.x, 0.0,
0.0, 0.0, 0.0, 1.0 );
mat4 ry = mat4( c.y, 0.0, -s.y, 0.0,
0.0, 1.0, 0.0, 0.0,
s.y, 0.0, c.y, 0.0,
0.0, 0.0, 0.0, 1.0 );
mat4 rz = mat4( c.z, -s.z, 0.0, 0.0,
s.z, c.z, 0.0, 0.0,
0.0, 0.0, 1.0, 0.0,
0.0, 0.0, 0.0, 1.0 );
fColor = vColor;
gl_Position = rz * ry * rx * vPosition;
}
</script>
<script id="fragment-shader" type="x-shader/x-fragment">
precision mediump float;
varying vec4 fColor;
void
main()
{
gl_FragColor = fColor;
}
</script>
<script src="https://esangel.github.io/WebGL/Common/webgl-utils.js"></script>
<script src="https://esangel.github.io/WebGL/Common/initShaders.js"></script>
<script src="https://esangel.github.io/WebGL/Common/MV.js"></script>
If you want perspective 3D instead of orthographic 3D you'd probably use a perspective matrix

Trying to use 'attribute mat4' and not 'attribute uniform'

I have this variable 'xformMatrix' and each element holds an array of 16 values:
var xformMatrix =
[[0.9238795325112867, 0.3826834323650898, 0.0,
-0.3826834323650898, 0.9238795325112867, 0.0, 0.0,
0.0, 0.0, 1.0, 0.0,
0.0, 0.0, 0.0, 1.0],
[0.7071067811865476, 0.7071067811865475, 0.0, 0.0,
-0.7071067811865475, 0.7071067811865476, 0.0, 0.0,
0.0, 0.0, 1.0, 0.0,
0.0, 0.0, 0.0, 1.0],
[0.38268343236508984, 0.9238795325112867, 0.0, 0.0,
-0.9238795325112867, 0.38268343236508984, 0.0, 0.0,
0.0, 0.0, 1.0, 0.0,
0.0, 0.0, 0.0, 1.0],
[6.123233995736766e-17, 1, 0.0, 0.0,
-1, 6.123233995736766e-17, 0.0, 0.0,
0.0, 0.0, 1.0, 0.0,
0.0, 0.0, 0.0, 1.0]]
I am trying to use a 4x4 matrix as an attribute to rotate my triangles without having to fill in my vertices array anymore than what it is. I believe I am getting confused where gl.vertexAttribPointer is asking for a size:
gl.vertexAttribPointer(a_xformMatrix, 1, gl.FLOAT, false, 6 *
Float32Array.BYTES_PER_ELEMENT, 5 * Float32Array.BYTES_PER_ELEMENT);
This is how my shaders are setup:
var VSHADER_SOURCE =
'attribute vec4 a_Position;\n' +
'attribute mat4 a_xformMatrix;\n' +
'attribute vec3 a_Color;\n' +
'varying vec3 v_Color;\n' +
'void main() {\n' +
' v_Color = a_Color;\n' +
' gl_Position = a_xformMatrix * a_Position;\n' +
'}\n';
// Fragment shader program
var FSHADER_SOURCE =
'precision mediump float;\n' +
'varying vec3 v_Color;\n' +
'void main() {\n' +
' gl_FragColor = vec4(v_Color, 1.0);\n' +
'}\n';
An example of my function:
function initVertexBuffers(gl) {
// Triangle Verticies
var vertices = new Float32Array(
[ // x, y r, g, b rotate matrix
0.0, 0.5, 1.0, 0.0, 0.0, xformMatrix[0],
-0.5, -0.5, 1.0, 0.0, 0.0, xformMatrix[0],
0.5, -0.5, 1.0, 0.0, 0.0, xformMatrix[0],
0.0, 0.5, 0.0, 1.0, 0.0, xformMatrix[1],
-0.5, -0.5, 0.0, 1.0, 0.0, xformMatrix[1],
0.5, -0.5, 0.0, 1.0, 0.0, xformMatrix[1],
0.0, 0.5, 0.0, 0.0, 1.0, xformMatrix[2],
-0.5, -0.5, 0.0, 0.0, 1.0, xformMatrix[2],
0.5, -0.5, 0.0, 0.0, 1.0, xformMatrix[2],
0.0, 0.5, 1.0, 0.0, 1.0, xformMatrix[3],
-0.5, -0.5, 1.0, 0.0, 1.0, xformMatrix[3],
0.5, -0.5, 1.0, 0.0, 1.0, xformMatrix[3]
]);
var n = 12; // The number of vertices
// Create a buffer object
var vertexBuffer = gl.createBuffer();
if (!vertexBuffer) {
console.log('Failed to create the buffer object');
return false;
}
// Bind the buffer object to target
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
// Write date into the buffer object
gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);
// Assign the buffer object to the position attribute variable
var a_Position = gl.getAttribLocation(gl.program, 'a_Position');
if (a_Position < 0) {
console.log('Failed to get the storage location of a_Position');
return -1;
}
// Assign the buffer object to the color attribute variable
var a_Color = gl.getAttribLocation(gl.program, 'a_Color');
if (a_Color < 0) {
console.log('Failed to get the storage location of a_Color');
return -1;
}
// Assign the buffer object to the rotation matrix attribute variable
var a_xformMatrix = gl.getAttribLocation(gl.program, 'a_xformMatrix');
if (a_xformMatrix < 0) {
console.log('Failed to get the storage location of a_xformMatrix');
return -1;
}
// Set Pointers
gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 6 * Float32Array.BYTES_PER_ELEMENT, 0);
gl.vertexAttribPointer(a_Color, 3, gl.FLOAT, false, 6 * Float32Array.BYTES_PER_ELEMENT, 2 * Float32Array.BYTES_PER_ELEMENT);
gl.vertexAttribPointer(a_xformMatrix, 1, gl.FLOAT, false, 6 * Float32Array.BYTES_PER_ELEMENT, 5 * Float32Array.BYTES_PER_ELEMENT);
// Enable the assignment to a_Position variable
gl.enableVertexAttribArray(a_Position);
gl.enableVertexAttribArray(a_Color);
gl.enableVertexAttribArray(a_xformMatrix);
return n;
}
The final output should look something like this:
Is there a trick to doing it this way or am I just going in the wrong direction?
What you're doing is not common
You've got x, y, r, g, b, m[0], m[1], m[2], m[3], m[4], m[5], m[6], m[7], m[8], m[9], m[10], m[11], m[12], m[13], m[14], m[15] per vertex so your stride, since you're trying to put all the data in the same buffer, would be
21 * Float32Array.BYTES_PER_ELEMENT
Then you need to set 4 attributes for the mat4 and the size for each is 4 (4 attributes, size 4 each = 16 values of the matrix)
// Set Pointers
const stride = 21 * Float32Array.BYTES_PER_ELEMENT;
gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, stride, 0);
gl.vertexAttribPointer(a_Color, 3, gl.FLOAT, false, stride, 2 * Float32Array.BYTES_PER_ELEMENT);
gl.vertexAttribPointer(a_xformMatrix + 0, 4, gl.FLOAT, false, stride, 5 * Float32Array.BYTES_PER_ELEMENT);
gl.vertexAttribPointer(a_xformMatrix + 1, 4, gl.FLOAT, false, stride, 9 * Float32Array.BYTES_PER_ELEMENT);
gl.vertexAttribPointer(a_xformMatrix + 2, 4, gl.FLOAT, false, stride, 13 * Float32Array.BYTES_PER_ELEMENT);
gl.vertexAttribPointer(a_xformMatrix + 3, 4, gl.FLOAT, false, stride, 17 * Float32Array.BYTES_PER_ELEMENT);
And further this code isn't putting the matrix data into the Float32Array. You could write some code to merge the data or if you want to do it by hand
var vertices = new Float32Array(
[ // x, y r, g, b rotate matrix
0.0, 0.5, 1.0, 0.0, 0.0,
xformMatrix[0][0], xformMatrix[0][1], xformMatrix[0][2], xformMatrix[0][3],
xformMatrix[0][4], xformMatrix[0][5], xformMatrix[0][6], xformMatrix[0][7],
xformMatrix[0][8], xformMatrix[0][9], xformMatrix[0][10], xformMatrix[0][11],
xformMatrix[0][12], xformMatrix[0][13], xformMatrix[0][14], xformMatrix[0][15],
... repeat for the next vertex ..
]);
Note I didn't bother to check if you make all those changes if your code will work. Only that based on what you said you are trying to do those are the most obvious issues.
You can probably see that if you go this way you have a ton of data to update as you try to rotate the triangles so you probably want to find a different approach.
Check out these tutorials. The first article draws a bunch of rectangles in different colors. It uses one draw call per color which is the most common way. It then builds up to using matrices in the following articles.
You could also just pass in a rotation per triangle and compute the rotation in the shader. You'd then have just one rotation value per triangle per vertex instead of a matrix per triangle per vertex. You'd have to update 3 rotations per triangle to animate them.
You could also indirect through a texture so instead of a rotation per triangle per vertex you have a triangle ID per triangle per vertex. So the first 3 vertices get ID = 0, the next 3 ID = 1, etc. You pass that in as an attribute then you could use that to generate rotation as in rotation = ID * constant or you could use that id to look up a rotation in a texture as in rotation = texture2D(textureWithRotationData, vec2((id + .5) / textureWidth, 0.5).r. The advantage to this method is you'd only have to update 1 rotation per triangle. The one in the texture.

WebGL rendering a texture for a 2d sprite. Not showing up

Previously had a color vertex for rendering this small square, now i want to use an image. Im using an image sprite i had lying around that sits at 64x128 wide.
I'm not getting any errors, but nothing is showing up either. First the shaders:
<script id="shader-fs" type="x-shader/x-fragment">
precision mediump float;
varying vec2 vTextureCoord;
uniform sampler2D uSampler;
void main(void) {
gl_FragColor = texture2D(uSampler, vec2(vTextureCoord.s, vTextureCoord.t));
}
</script>
<script id="shader-vs" type="x-shader/x-vertex">
attribute vec3 aVertexPosition;
attribute vec2 aTextureCoord;
uniform mat4 uMVMatrix;
uniform mat4 uPMatrix;
varying vec2 vTextureCoord;
void main(void) {
gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
vTextureCoord = aTextureCoord;
}
</script>
For the buffers:
initBuffers: function () {
this.planePositionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, this.planePositionBuffer);
var vertices = [
1.0, 1.0, 0.0,
-1.0, 1.0, 0.0,
1.0, -1.0, 0.0,
-1.0, -1.0, 0.0
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
this.planePositionBuffer.itemSize = 3;
this.planePositionBuffer.numItems = 4;
this.textureBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, this.textureBuffer);
var textureCoords = [
0.0, 1.0,
0.0, 0.0,
1.0, 1.0,
1.0, 0.0
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(textureCoords), gl.STATIC_DRAW);
this.textureBuffer.itemSize = 2;
this.textureBuffer.numItems = 4;
}
Initializing the shaders:
initShaders: function () {
this.shader = new Shader("shader");
var shaderProgram = this.shader.shaderProgram;
shaderProgram.vertexPositionAttribute = gl.getAttribLocation(shaderProgram, "aVertexPosition");
gl.enableVertexAttribArray(shaderProgram.vertexPositionAttribute);
shaderProgram.textureCoordAttribute = gl.getAttribLocation(shaderProgram, "aTextureCoord");
gl.enableVertexAttribArray(shaderProgram.textureCoordAttribute);
shaderProgram.pMatrixUniform = gl.getUniformLocation(shaderProgram, "uPMatrix");
shaderProgram.mvMatrixUniform = gl.getUniformLocation(shaderProgram, "uMVMatrix");
shaderProgram.samplerUniform = gl.getUniformLocation(shaderProgram, "uSampler");
}
And the draw call.
draw: function () {
this.resize();
var delta = this.getDeltaTime();
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
mat4.identity(this.mvMatrix);
mat4.identity(this.pMatrix);
mat4.perspective(this.pMatrix, 45 * Math.PI / 180, gl.canvas.clientWidth / gl.canvas.clientHeight, 0.1, 100.0);
mat4.translate(this.pMatrix, this.pMatrix, [0.0, 0.0, -50.0]);
var shaderProgram = this.shader.shaderProgram;
for (var i = 0; i < this.objects.length; i++) {
this.objects[i].update(delta, this.mvMatrix);
}
gl.bindBuffer(gl.ARRAY_BUFFER, this.planePositionBuffer);
gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, this.planePositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ARRAY_BUFFER, this.textureBuffer);
gl.vertexAttribPointer(shaderProgram.textureCoordAttribute, this.textureBuffer.itemSize, gl.FLOAT, false, 0, 0);
gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, me.loader.getImage('test'));
gl.uniform1i(shaderProgram.samplerUniform, 0);
this.setMatrixUniforms();
gl.drawArrays(gl.TRIANGLE_STRIP, 0, this.planePositionBuffer.numItems);
requestAnimationFrame(this.draw.bind(this));
},
I based the texture coords off of an article i found on opengles drawing on android. The idea was the coords should be in order of bottom left -> top left -> bottom right -> top right.
Full source code for its broken state can be found here in addition to the snippets above: https://github.com/agmcleod/webgl-2dexperiment/tree/13f31f70037fdd4515c1336423337a1e82ab4e89
Looks as if the WebGL code was all correct. However, I was never invoking the function bindAllTextures to actually set up the texture with webgl for rendering.

How to use multiple textures in WebGL?

I wanted to use 6 different textures on a cube, one per side, but can't find the mistake. Here's my current code:
var texturen = new Array();
function initTexture(sFilename,texturen)
{
var anz = texturen.length;
texturen[anz] = gl.createTexture();
texturen[anz].image = new Image();
texturen[anz].image.onload = function()
{
gl.bindTexture(gl.TEXTURE_2D, texturen[anz]);
gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, false);
gl.texImage2D
(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, texturen[anz].image);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.bindTexture(gl.TEXTURE_2D, null);
}
texturen[anz].image.src = sFilename;
}
var mvMatrix = mat4.create();
var mvMatrixStack = [];
var pMatrix = mat4.create();
function mvPushMatrix() {
var copy = mat4.create();
mat4.set(mvMatrix, copy);
mvMatrixStack.push(copy);
}
function mvPopMatrix() {
if (mvMatrixStack.length == 0) {
throw "Invalid popMatrix!";
}
mvMatrix = mvMatrixStack.pop();
}
function setMatrixUniforms() {
gl.uniformMatrix4fv(shaderProgram.pMatrixUniform, false, pMatrix);
gl.uniformMatrix4fv(shaderProgram.mvMatrixUniform, false, mvMatrix);
}
function degToRad(degrees) {
return degrees * Math.PI / 180;
}
var cubeVertexPositionBuffer;
var cubeVertexTextureCoordBuffer;
var cubeVertexIndexBuffer;
var cubeVertexPositionBuffer1;
var cubeVertexTextureCoordBuffer1;
var cubeVertexIndexBuffer1;
function initBuffers() {
cubeVertexPositionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
vertices = [
// Front face
-1.0, -1.0, 1.0,
1.0, -1.0, 1.0,
1.0, 1.0, 1.0,
-1.0, 1.0, 1.0,
// Back face
-1.0, -1.0, -1.0,
-1.0, 1.0, -1.0,
1.0, 1.0, -1.0,
1.0, -1.0, -1.0,
// Top face
-1.0, 1.0, -1.0,
-1.0, 1.0, 1.0,
1.0, 1.0, 1.0,
1.0, 1.0, -1.0,
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
cubeVertexPositionBuffer.itemSize = 3;
cubeVertexPositionBuffer.numItems = 12;
cubeVertexPositionBuffer1 = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer1);
vertices = [
// Bottom face
-1.0, -1.0, -1.0,
1.0, -1.0, -1.0,
1.0, -1.0, 1.0,
-1.0, -1.0, 1.0,
// Right face
1.0, -1.0, -1.0,
1.0, 1.0, -1.0,
1.0, 1.0, 1.0,
1.0, -1.0, 1.0,
// Left face
-1.0, -1.0, -1.0,
-1.0, -1.0, 1.0,
-1.0, 1.0, 1.0,
-1.0, 1.0, -1.0,
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
cubeVertexPositionBuffer1.itemSize = 3;
cubeVertexPositionBuffer1.numItems = 12;
cubeVertexTextureCoordBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexTextureCoordBuffer);
var textureCoords = [
// Front face
0.0, 0.0,
1.0, 0.0,
1.0, 1.0,
0.0, 1.0,
// Back face
1.0, 0.0,
1.0, 1.0,
0.0, 1.0,
0.0, 0.0,
// Top face
0.0, 1.0,
0.0, 0.0,
1.0, 0.0,
1.0, 1.0,
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(textureCoords), gl.STATIC_DRAW);
cubeVertexTextureCoordBuffer.itemSize = 2;
cubeVertexTextureCoordBuffer.numItems = 12;
cubeVertexTextureCoordBuffer1 = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexTextureCoordBuffer1);
var textureCoords = [
// Bottom face
1.0, 1.0,
0.0, 1.0,
0.0, 0.0,
1.0, 0.0,
// Right face
1.0, 0.0,
1.0, 1.0,
0.0, 1.0,
0.0, 0.0,
// Left face
0.0, 0.0,
1.0, 0.0,
1.0, 1.0,
0.0, 1.0,
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(textureCoords), gl.STATIC_DRAW);
cubeVertexTextureCoordBuffer1.itemSize = 2;
cubeVertexTextureCoordBuffer1.numItems = 12;
cubeVertexIndexBuffer = gl.createBuffer();
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
var cubeVertexIndices = [
0, 1, 2, 0, 2, 3, // Front face
4, 5, 6, 4, 6, 7, // Back face
8, 9, 10, 8, 10, 11, // Top face
];
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(cubeVertexIndices), gl.STATIC_DRAW);
cubeVertexIndexBuffer.itemSize = 1;
cubeVertexIndexBuffer.numItems = 18;
cubeVertexIndexBuffer1 = gl.createBuffer();
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer1);
var cubeVertexIndices = [
12, 13, 14, 12, 14, 15, // Bottom face
16, 17, 18, 16, 18, 19, // Right face
20, 21, 22, 20, 22, 23 // Left face
];
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(cubeVertexIndices), gl.STATIC_DRAW);
cubeVertexIndexBuffer1.itemSize = 1;
cubeVertexIndexBuffer1.numItems = 18;
}
var xRot = 0;
var yRot = 0;
var zRot = 0;
function drawScene() {
gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
mat4.perspective(45, gl.viewportWidth / gl.viewportHeight, 0.1, 100.0, pMatrix);
mat4.identity(mvMatrix);
mat4.translate(mvMatrix, [0.0, 0.0, -5.0]);
mat4.rotate(mvMatrix, degToRad(xRot), [1, 0, 0]);
mat4.rotate(mvMatrix, degToRad(yRot), [0, 1, 0]);
mat4.rotate(mvMatrix, degToRad(zRot), [0, 0, 0]);
setMatrixUniforms();
gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, texturen[0]);
gl.vertexAttribPointer
(textureCoordAttribute, cubeVertexTextureCoordBuffer.itemSize, gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
gl.vertexAttribPointer
(shaderProgram.vertexPositionAttribute,cubeVertexPositionBuffer.itemSize,
gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
gl.drawElements(gl.TRIANGLES, cubeVertexIndexBuffer.numItems, gl.UNSIGNED_SHORT, 0);
gl.activeTexture(gl.TEXTURE1);
gl.bindTexture(gl.TEXTURE_2D, texturen[1]);
gl.vertexAttribPointer
(textureCoordAttribute, cubeVertexTextureCoordBuffer1.itemSize, gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer1);
gl.vertexAttribPointer
(shaderProgram.vertexPositionAttribute,cubeVertexPositionBuffer1.itemSize,
gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer1);
gl.drawElements(gl.TRIANGLES, cubeVertexIndexBuffer1.numItems, gl.UNSIGNED_SHORT, 0);
}
i just divided it into two parts, trying to make a test with 2 different pics. And what are the cubeVertexIndexBuffers for exactly?
First off, the short answer: Replace the last 10 lines of your code with the following and I think it should work.
gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, texturen[1]);
gl.vertexAttribPointer(textureCoordAttribute, cubeVertexTextureCoordBuffer1.itemSize, gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer1);
gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute,cubeVertexPositionBuffer1.itemSize, gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
gl.drawElements(gl.TRIANGLES, cubeVertexIndexBuffer.numItems, gl.UNSIGNED_SHORT, 0);
The key changes are:
activeTexture is still TEXTURE0 (you're only using one texture at a time here)
Using cubeVertexIndexBuffer instead of cubeVertexIndexBuffer1, which contained out-of-range indicies
For a better explanation of what the indices are actually used for I'll refer you to this SO question as I'd rather not repeat all that here.
Now, on to the more general answer.
There are two basic ways to handle the issue of using different textures on different faces. The first and simpler method is to do exactly what you are doing here: Render the object in pieces, binding a different texture for each piece. Though not strictly the most efficient way to accomplish the effect it is nevertheless the most common way to handle it in high-performance applications such as games simply because it offers a lot of flexibility, especially when your materials are more complex than a simple diffuse texture.
There is a simple way that you can improve the performance of code like yours for a case like this, though. The vertices/indices don't have to be broken into separate buffers per-texture. You could instead combine them all into a single buffer and render them with different offsets like so:
// On Init
var vertBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vertBuffer);
var vertices = [
// Vertex values for all 6 faces
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
var indexBuffer = gl.createBuffer();
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
var indices = [
// Index values for all 6 faces
];
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(indices), gl.STATIC_DRAW);
// On Draw
// Setup the shader and uniforms and all that jazz
gl.bindBuffer(gl.ARRAY_BUFFER, vertBuffer);
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
gl.vertexAttribPointer(// Blah blah blah...);
// Draw face 0
gl.bindTexture(gl.TEXTURE_2D, texture[0]);
gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_SHORT, 0);
// Draw face 1
gl.bindTexture(gl.TEXTURE_2D, texture[1]);
gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_SHORT, 12);
// Draw face 2
gl.bindTexture(gl.TEXTURE_2D, texture[2]);
gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_SHORT, 24);
// .. And so on to face 5
// Draw face 2
gl.bindTexture(gl.TEXTURE_2D, texture[5]);
gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_SHORT, 60);
What's going on here is that each call to drawElements only draws 2 triangles (6 vertices, the second parameter of the call), but each call is offset into the index buffer so that it starts on a different face. (fourth parameter of the call, which indicates a byte offset. Each index is a Uint16, so 2 bytes per index. 12 == "start on index[6]") This way all of the binding and setup only happens once, and each draw call only has to change the state that is actually necessary (the texture).
The other way to handle this, which is faster but harder to generalize, is to bind an array of textures to a shader uniform and use another vertex attribute to index into the array within the shader. I'm not going to detail the code for this approach but it should be relatively easy to set up once you're comfortable with WebGL shader use. If you have further questions about this specific approach it would be best to ask in a different SO question so as not to overload this one.

Categories