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Three.js global heightmap is not showing the expected result

I wanted to create a model of earth using a global 4k height map that I found online. I found this open source script that can do this.
function createGeometryFromMap() {
var depth = 512;
var width = 512;
var spacingX = 3;
var spacingZ = 3;
var heightOffset = 2;
var canvas = document.createElement('canvas');
canvas.width = 512;
canvas.height = 512;
var ctx = canvas.getContext('2d');
var img = new Image();
img.src = "assets/earth.jpg";
img.onload = function () {
// draw on canvas
ctx.drawImage(img, 0, 0);
var pixel = ctx.getImageData(0, 0, width, depth);
var geom = new THREE.Geometry;
var output = [];
for (var x = 0; x < depth; x++) {
for (var z = 0; z < width; z++) {
// get pixel
// since we're grayscale, we only need one element
var yValue = pixel.data[z * 4 + (depth * x * 4)] / heightOffset;
var vertex = new THREE.Vector3(x * spacingX, yValue, z * spacingZ);
geom.vertices.push(vertex);
}
}
// we create a rectangle between four vertices, and we do
// that as two triangles.
for (var z = 0; z < depth - 1; z++) {
for (var x = 0; x < width - 1; x++) {
// we need to point to the position in the array
// a - - b
// | x |
// c - - d
var a = x + z * width;
var b = (x + 1) + (z * width);
var c = x + ((z + 1) * width);
var d = (x + 1) + ((z + 1) * width);
var face1 = new THREE.Face3(a, b, d);
var face2 = new THREE.Face3(d, c, a);
face1.color = new THREE.Color(scale(getHighPoint(geom, face1)).hex());
face2.color = new THREE.Color(scale(getHighPoint(geom, face2)).hex())
geom.faces.push(face1);
geom.faces.push(face2);
}
}
geom.computeVertexNormals(true);
geom.computeFaceNormals();
geom.computeBoundingBox();
var zMax = geom.boundingBox.max.z;
var xMax = geom.boundingBox.max.x;
var mesh = new THREE.Mesh(geom, new THREE.MeshLambertMaterial({
vertexColors: THREE.FaceColors,
color: 0x666666,
shading: THREE.NoShading
}));
mesh.translateX(-xMax / 2);
mesh.translateZ(-zMax / 2);
scene.add(mesh);
mesh.name = 'valley';
};
}
function getHighPoint(geometry, face) {
var v1 = geometry.vertices[face.a].y;
var v2 = geometry.vertices[face.b].y;
var v3 = geometry.vertices[face.c].y;
return Math.max(v1, v2, v3);
}
When I tried the demo heightmaps of Grand Canyon and Hawaii that came with the download, they seemed to be fine. However, when I tried to implement my global heightmap into this, the result was not displaying what I needed.
This is the terrain of Grand Canyon:
This is the global heightmap that I am using:
And this is the result I am getting for the 3D terrain of the world:
It's obvious that something is wrong, because that is not the world.

When you tell your 2D canvas context to .drawImage(), it's going to draw a 4000 pixels image over a 512 pixels canvas. That's how it's defined in the MDN documents if you only use three img, dx, dy arguments.
You could either:
Draw the Earth image smaller to fit inside your 512x512 pixels canvas by using the 4th and 5th arguments of dWidth, dHeight.
Make your canvas larger to match the width and height dimensions of your Earth image.

EaselJS how to update text

I'm trying to update the circles and text above each circle when mouseoveer event happens, however I only successfully update the circles, but not sure about how to update the text.
for (var i = 0; i < 100; i++) {
var circle = new createjs.Shape();
var r = 7;
var x = window.innerWidth * Math.random();
var y = window.innerHeight * Math.random();
var color = colors[Math.floor(i % colors.length)];
var alpha = 0.2 + Math.random() * 0.5;
circle.color = color;
circle.alpha = alpha;
circle.radius = r;
circle.graphics.beginFill(color).drawCircle(0, 0, r);
circle.x = x;
circle.y = y;
var txt = new createjs.Text(i.toString(), "11px Arial", "#FFF");
txt.x = x - 4;
txt.y = y - 18;
var con = new createjs.Container();
con.addChild(circle, txt);
con.addEventListener("mouseover", function(event) {
event.target.graphics.clear().beginFill(event.target.color).drawCircle(0, 0, 15).endFill();
event.target.text = "dsfasd";
stage.update(event);
});
stage.addChild(con);
}

In your listener, target refers to the container itself. But event.target.text is not a reference to the text object added as a child inside it. In order to access the second child, you need to do event.target.children[1].

How to set onclick event in moving object in canvas?

How to set on click event in moving object in canvas? Also how to move the object bottom to top in canvas.I am newly in javascript i am going to develop the sample like when the page open, objects like square and circle randomly come from bottom of the page and move to top automatically.

You need to establish an array that will have your moving objects in it. When the onclick handler fires, check to see if the coordinates of the click are inside any of the objects in the array.
On each animation frame, move your objects up by subtracting some of the y coordinate from each object.
//width and height of canvas...
var rW = 400;
var rH = 500;
var coinImage = getCoinImage();
var coinsOnScreen = [];
var risingSpeed = 100; //pixels per second...
var coinSize = 75;
var lastAnimationTime = 0;
var howLongUntilNextCoin = 1000;
var nextCoinOnScreen = 0;
function doDraw() {
var can = document.getElementById("myCanvas");
can.width = rW;
can.height = rH;
var context = can.getContext("2d");
//Erase the canvas
context.fillStyle = "#FFFFFF";
context.fillRect(0, 0, rW, rH);
if (new Date().getTime() - nextCoinOnScreen > 0) {
var newX = Math.floor(Math.random() * rW) + 1;
var newY = rH + 50;
var newCoin = {
x: newX,
y: newY
};
coinsOnScreen.push(newCoin);
nextCoinOnScreen = new Date().getTime() + howLongUntilNextCoin;
}
//Now draw the coins
if (lastAnimationTime != 0) {
var deltaTime = new Date().getTime() - lastAnimationTime;
var coinRisePixels = Math.floor((deltaTime * risingSpeed) / 1000);
var survivingCoins = [];
for (var i = 0; i < coinsOnScreen.length; i++) {
var coin = coinsOnScreen[i];
coin.y = coin.y - coinRisePixels;
//the stl variable controlls the alpha of the image
if (coin.y + 50 > 0) {
context.drawImage(coinImage, coin.x, coin.y);
//this coin is still on the screen, so promote it to the new array...
survivingCoins.push(coin);
}
}
coinsOnScreen = survivingCoins;
}
lastAnimationTime = new Date().getTime();
//Wait, and then call this function again to animate:
setTimeout(function() {
doDraw();
}, 30);
}
function setupClickHandler() {
var can = document.getElementById("myCanvas");
//Here is the onclick handler
can.onclick = function(e) {
var x = e.clientX;
var y = e.clientY;
var survivingCoins = [];
for (var i = 0; i < coinsOnScreen.length; i++) {
var coin = coinsOnScreen[i];
//check to see if this coin has been clicked...
if (x > coin.x && x < coin.x + coinSize && y > coin.y && y < coin.y + coinSize) {
//ths coin will disappear because it is not inserted into the new array...
console.log("Coin was clicked!! " + x + " " + y);
} else {
survivingCoins.push(coin);
}
}
coinsOnScreen = survivingCoins;
};
}
doDraw();
setupClickHandler();
function getCoinImage() {
var image = new Image(50, 50);
image.src = "data:image/png;base64,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";
return image;
}
<canvas id="myCanvas"></canvas>

Create color gradient describing discrete distribution of points

I am making a map that renders position of game objects (Project Zomboid zombies):
As user zooms out, single dots are no longer useful. Instead, I'd like to render distribution of zombies on an area using red color gradient. I tried to loop over all zombies for every rendered pixel and color it reciprocally to the sum of squared distances to the zombies. The result:
That's way too blurry. Also the results are more influenced by the zombies that are AWAY from the points - I need to influence them more by the zombies that are CLOSE. So what this is is just math. Here's the code I used:
var h = canvas.height;
var w = canvas.width;
// To loop over more than 1 pixel (performance)
var tileSize = 10;
var halfRadius = Math.floor(tileSize/2);
var time = performance.now();
// "Squared" because we didnt unsquare it
function distanceSquared(A, B) {
return (A.x-B.x)*(A.x-B.x)+(A.y-B.y)*(A.y-B.y);
}
// Loop for every x,y pixel (or region of pixels)
for(var y=0; y<h; y+=tileSize) {
for(var x=0; x<w; x+=tileSize) {
// Time security - stop rendering after 1 second
if(performance.now()-time>1000) {
x=w;y=h;break;
}
// Convert relative canvas offset to absolute point on the map
var point = canvasPixeltoImagePixel(x, y);
// For every zombie add sqrt(distance from this point to zombie)
var distancesRoot = 0;
// Loop over the zombies
var zombieCoords;
for(var i=0; i<zombies_length; i++) {
// Get single zombie coordinates as {x:0, y:0}
if((coords=zombies[i].pixel)==null)
coords = zombies[i].pixel = tileToPixel(zombies[i].coordinates[0], zombies[i].coordinates[1], drawer);
// square root is a) slow and b) probably not what I want anyway
var dist = distanceSquared(coords, point);
distancesRoot+=dist;
}
// The higher the sum of distances is, the more intensive should the color be
var style = 'rgba(255,0,0,'+300000000/distancesRoot+')';
// Kill the console immediatelly
//console.log(style);
// Maybe we should sample and cache the transparency styles since there's limited ammount of colors?
ctx.fillStyle = style;
ctx.fillRect(x-halfRadius,y-halfRadius,tileSize,tileSize);
}
}
I'm pretty fine with theoretical explanation how to do it, though if you make simple canvas example with some points, what would be awesome.

This is an example of a heat map. It's basically gradient orbs over points and then ramping the opacity through a heat ramp. The more orbs cluster together the more solid the color which can be shown as an amplified region with the proper ramp.
update
I cleaned up the variables a bit and put the zeeks in an animation loop. There's an fps counter to see how it's performing. The gradient circles can be expensive. We could probably do bigger worlds if we downscale the heat map. It won't be as smooth looking but will compute a lot faster.
update 2
The heat map now has an adjustable scale and as predicted we get an increase in fps.
if (typeof app === "undefined") {
var app = {};
}
app.zeeks = 200;
app.w = 600;
app.h = 400;
app.circleSize = 50;
app.scale = 0.25;
init();
function init() {
app.can = document.getElementById('can');
app.ctx = can.getContext('2d');
app.can.height = app.h;
app.can.width = app.w;
app.radius = Math.floor(app.circleSize / 2);
app.z = genZ(app.zeeks, app.w, app.h);
app.flip = false;
// Make temporary layer once.
app.layer = document.createElement('canvas');
app.layerCtx = app.layer.getContext('2d');
app.layer.width = Math.floor(app.w * app.scale);
app.layer.height = Math.floor(app.h * app.scale);
// Make the gradient canvas once.
var sCircle = Math.floor(app.circleSize * app.scale);
app.radius = Math.floor(sCircle / 2);
app.gCan = genGradientCircle(sCircle);
app.ramp = genRamp();
// fps counter
app.frames = 0;
app.fps = "- fps";
app.fpsInterval = setInterval(calcFps, 1000);
// start animation
ani();
flicker();
}
function calcFps() {
app.fps = app.frames + " fps";
app.frames = 0;
}
// animation loop
function ani() {
app.frames++;
var ctx = app.ctx;
var w = app.w;
var h = app.h;
moveZ();
//ctx.clearRect(0, 0, w, h);
ctx.fillStyle = "#006600";
ctx.fillRect(0, 0, w, h);
if (app.flip) {
drawZ2();
drawZ();
} else {
drawZ2();
}
ctx.fillStyle = "#FFFF00";
ctx.fillText(app.fps, 10, 10);
requestAnimationFrame(ani);
}
function flicker() {
app.flip = !app.flip;
if (app.flip) {
setTimeout(flicker, 500);
} else {
setTimeout(flicker, 5000);
}
}
function genGradientCircle(size) {
// gradient image
var gCan = document.createElement('canvas');
gCan.width = gCan.height = size;
var gCtx = gCan.getContext('2d');
var radius = Math.floor(size / 2);
var grad = gCtx.createRadialGradient(radius, radius, radius, radius, radius, 0);
grad.addColorStop(1, "rgba(255,255,255,.65)");
grad.addColorStop(0, "rgba(255,255,255,0)");
gCtx.fillStyle = grad;
gCtx.fillRect(0, 0, gCan.width, gCan.height);
return gCan;
}
function genRamp() {
// Create heat gradient
var heat = document.createElement('canvas');
var hCtx = heat.getContext('2d');
heat.width = 256;
heat.height = 5;
var linGrad = hCtx.createLinearGradient(0, 0, heat.width, heat.height);
linGrad.addColorStop(1, "rgba(255,0,0,.75)");
linGrad.addColorStop(0.5, "rgba(255,255,0,.03)");
linGrad.addColorStop(0, "rgba(255,255,0,0)");
hCtx.fillStyle = linGrad;
hCtx.fillRect(0, 0, heat.width, heat.height);
// create ramp from gradient
var ramp = [];
var imageData = hCtx.getImageData(0, 0, heat.width, 1);
var d = imageData.data;
for (var x = 0; x < heat.width; x++) {
var i = x * 4;
ramp[x] = [d[i], d[i + 1], d[i + 2], d[i + 3]];
}
return ramp;
}
function genZ(n, w, h) {
var a = [];
for (var i = 0; i < n; i++) {
a[i] = [
Math.floor(Math.random() * w),
Math.floor(Math.random() * h),
Math.floor(Math.random() * 3) - 1,
Math.floor(Math.random() * 3) - 1
];
}
return a;
}
function moveZ() {
var w = app.w
var h = app.h;
var z = app.z;
for (var i = 0; i < z.length; i++) {
var s = z[i];
s[0] += s[2];
s[1] += s[3];
if (s[0] > w || s[0] < 0) s[2] *= -1;
if (s[1] > w || s[1] < 0) s[3] *= -1;
}
}
function drawZ() {
var ctx = app.ctx;
var z = app.z;
ctx.fillStyle = "#FFFF00";
for (var i = 0; i < z.length; i++) {
ctx.fillRect(z[i][0] - 2, z[i][1] - 2, 4, 4);
}
}
function drawZ2() {
var ctx = app.ctx;
var layer = app.layer;
var layerCtx = app.layerCtx;
var gCan = app.gCan;
var z = app.z;
var radius = app.radius;
// render gradients at coords onto layer
for (var i = 0; i < z.length; i++) {
var x = Math.floor((z[i][0] * app.scale) - radius);
var y = Math.floor((z[i][1] * app.scale) - radius);
layerCtx.drawImage(gCan, x, y);
}
// adjust layer for heat ramp
var ramp = app.ramp;
// apply ramp to layer
var imageData = layerCtx.getImageData(0, 0, layer.width, layer.height);
d = imageData.data;
for (var i = 0; i < d.length; i += 4) {
if (d[i + 3] != 0) {
var c = ramp[d[i + 3]];
d[i] = c[0];
d[i + 1] = c[1];
d[i + 2] = c[2];
d[i + 3] = c[3];
}
}
layerCtx.putImageData(imageData, 0, 0);
// draw layer on world
ctx.drawImage(layer, 0, 0, layer.width, layer.height, 0, 0, app.w, app.h);
}
<canvas id="can" width="600" height="400"></canvas>

How to speed up nested for loops in IE?

I want to filter an image with a predefined filter mask in JavaScript using the HTML5 Canvas Element.
I found a solution which works fine:
//define source canvas
var srccanv = document.getElementById("src_canvas");
var ctx = srccanv.getContext("2d");
var w = srccanv.width;
var h = srccanv.height;
//just draw something into the canvas
ctx.beginPath();
ctx.fillStyle="gray";
ctx.fillRect(0,0,w,h);
ctx.lineWidth = 15;
ctx.strokeStyle = "lightgray";
ctx.moveTo(0,0);
ctx.lineTo(300,150);
ctx.stroke();
//define destination canvas
var dstcanv = document.getElementById("dst_canvas");
var dctx = dstcanv.getContext("2d");
var dstImageData = dctx.getImageData(0,0,dstcanv.width,dstcanv.height);
var dst = dstImageData.data;
//filtermask
var filtermask = [-1,-1,-1,0,0,0,1,1,1];
var side = Math.round(Math.sqrt(filtermask.length));
var halfSide = Math.floor(side/2);
var srcImageData = ctx.getImageData(0,0,w,h);
var src = srcImageData.data;
var sw = w;
var sh = h;
console.time('convolution');
// go through the destination image pixels
for (var y=1; y<h-1; y++) {
for (var x=1; x<w-1; x++) {
var sy = y;
var sx = x;
var dstOff = (y*w+x)*4;
// calculate the weighed sum of the source image pixels that
// fall under the convolution matrix
var r=0, g=0, b=0, a=0;
for (var cy=0; cy<side; cy++) {
for (var cx=0; cx<side; cx++) {
var scy = sy + cy - halfSide;
var scx = sx + cx - halfSide;
if (scy >= 0 && scy < sh && scx >= 0 && scx < sw) {
var srcOff = (scy*sw+scx)*4;
var wt = filtermask[cy*side+cx];
r += src[srcOff] * wt;
g += src[srcOff+1] * wt;
b += src[srcOff+2] * wt;
a += src[srcOff+3];
}
}
}
dst[dstOff] = r;
dst[dstOff+1] = g;
dst[dstOff+2] = b;
dst[dstOff+3] = 255;
}
}
console.timeEnd('convolution');
dctx.putImageData(dstImageData,0,0);
<canvas id="src_canvas"></canvas>
<canvas id="dst_canvas"></canvas>
or see this fiddle: https://jsfiddle.net/w0fuxt64/20/
But... I found out that the performance in IE11 is very bad. I tested my code with latest versions of firefox (38.5.2 ESR) and Chrome (47.0) and I got some results around 10-20ms for the filtering of an 300px by 150px canvas. (See time in developer console of your browser)
Testing with IE gave me results around 280ms! which is way too long to be useful for my purposes. Does anybody have any ideas how to dramatically improve this code for IE.
Thanks in advance
Beni