We Keep Coding

How to Create a Multidimenisonal PRNG?

I am working on a procedural terrain generator, but the 3d Map is constantly morphing and changing, calling for at least 4d noise (5d if I need to make it loop). I haven't found a good perlin/simplex noise library that will work in this many dimensions, so I thought this would be a good time to learn how those algorithms work. After starting to make my own "perlin" noise, I found a large problem. I need to get a psudo random value based on the nD coordinates of that point. So far I have found solutions online that use the dot product of a single point and a vector generated by the inputs, but those became very predictable very fast (I'm not sure why). I then tried a recursive approach (below), and this worked ok, but I got some weird behavior towards the edges.
Recursive 3d randomness attempt:
function Rand(seed = 123456, deg = 1){
let s = seed % 2147483647;
s = s < 1 ? s + 2147483647 : s;
while(deg > 0){
s = s * 16807 % 2147483647;
deg--;
}
return (s - 1) / 2147483646;
}
function DimRand(seed, args){
if(args.length < 2){
return Rand(seed, args[0]);
}else{
let zero = args[0];
args.shift();
return DimRand(Rand(seed, zero), args);
}
}
var T = 1;
var c = document.getElementById('canvas').getContext('2d');
document.getElementById('canvas').height = innerHeight;
document.getElementById('canvas').width = innerWidth;
c.width = innerWidth;
c.height = innerHeight;
var size = 50;
function display(){
for(let i = 0; i < 20; i ++){
for(let j = 0; j < 20; j ++){
var bright = DimRand(89,[i,j])*255
c.fillStyle = `rgb(${bright},${bright},${bright})`
c.fillRect(i*size, j*size, size, size);
}
}
T++;
}
window.onmousedown=()=>{display();}
And here is the result:
The top row was always 1 (White), the 2d row and first column were all 0 (Black), and the 3d row was always very dark (less than ≈ 0.3)
This might just be a bug, or I might have to just deal with it, but I was wondering if there was a better approach.

ThreeJS Maya like wireframe implementation

I'm trying to implement a wireframe which displays quads instead of tris using this code
var geo = new THREE.EdgesGeometry( _this.geometry ); // or WireframeGeometry
var mat = new THREE.LineBasicMaterial( { color: 0xffffff, linewidth: 2 } );
var wireframe = new THREE.LineSegments( geo, mat );
_this.scene.add( wireframe );
This produces the following when the model is rendered
As you can see from the image it is not displaying all of the edges, and is still displaying some tris. I need it to be similar to how Maya displays wireframes.
I have read that ThreeJS no longer supports Face4 which is why it always displays tris instead of quads, but i was wondering if there was a way around this? I have also seen some mention of using a pixel shader to display only the edges of a mesh but i havnt been able to understand/get that working.
I would love some assistance on this one, either using existing threejs functionality, or by using a pixel shader somehow.
This is the model source (http://pastebin.com/21XUKYbw)
Cheers

Answering this for anyone who stumbles upon this issue in the future.
Following on from a comment made by WestLangley, i have modified the code within WireframeGeometry.js to ignore rendering the interior diagonals that are present when rendering a wireframe, which gives the appearance of quad faces. Which is more familiar to 3d artists.
This is the change I've made to the bottom of WireframeGeometry.js. This is admittedly a pretty hacky fix. The alternative would be to compute the lines you want to display before threejs performs triangulation. You could store the pre triangluated faces in a separate buffer.
// non-indexed BufferGeometry
position = geometry.attributes.position;
var _i = 0;
for ( i = 0, l = ( position.count / 3 ); i < l; i ++ ) {
for ( j = 0; j < 3; j ++ )
// three edges per triangle, an edge is represented as (index1, index2)
// e.g. the first triangle has the following edges: (0,1),(1,2),(2,0)
// Added a simple check here to only push the vertices that are not diagonal lines
if(!(j == 2 && _i == 1) || !(j == 1 && _i == 0)){
index1 = 3 * i + j;
vertex.fromBufferAttribute(position, index1);
vertices.push(vertex.x, vertex.y, vertex.z);
index2 = 3 * i + ( ( j + 1 ) % 3 );
vertex.fromBufferAttribute(position, index2);
vertices.push(vertex.x, vertex.y, vertex.z);
}
}
_i++;
if(_i == 2){
_i = 0
}
}

Algorithm to convert a 2d voxel map to line sometimes gets stuck

I have a 2D voxel map for a game, which is a 2D array where 1 means ground and 0 means sky.
Example: all 1's in the array (ground) are green boxes
The algorithm starts at the leftmost ground voxel that touches the sky (red box in picture).
It will explore 8 neighbours of the current position to check if one of them is a ground voxel and also touches a sky voxel. This means it should be added to the groundline.
Example of the algorithm working (it's able to go in 'caves' too)
On this map it figured it out and returned a line across the ground.
In some situations it suddenly stops though, like on this map:
After about 10 loops it stopped creating the line.
Here's the code, with some explanatory comments in there:
voxelToLine() {
let voxels = this.voxels.length,//this.voxels is the 2d array
lineGround = [],
checkedVoxels = [],
nowChecking,
toCheck = [],
otherPaths = [],
done = false;
for (let y = 1; y < voxels - 1; y++)//sets first coordinate for line
if (this.voxels[0][y] && (!this.voxels[0][y - 1] || !this.voxels[1][y] || !this.voxels[0][y + 1])) {
lineGround[0] = [0, y / voxels];
nowChecking = [1, y];//search starts from this point
}
let looped = 0;
while (!done) {//continues search untill right side is located, or it got stuk (max 10*voxelmap width loops)
toCheck = nowChecking.neighbours(8, (n) => n[0] > 0 && n[0] < voxels - 1);//gets 8 neighbour points around current point, neighbours between 1 and (voxelwidth -1) get returned
let foundNew = false;
for (let i = 0; i < toCheck.length; i++) {//check every neighbour
let x = toCheck[i][0],
y = toCheck[i][1],
index = y * voxels + x;
if (!checkedVoxels.includes(index)) {
if (this.voxels[x][y] && (!this.voxels[x][y - 1] || !this.voxels[x + 1][y] || !this.voxels[x - 1][y] || !this.voxels[x][y + 1])) {
//if the neighbour is a floor voxel, and touches a skyvoxel this neighbour is added to the line
checkedVoxels.push(index);
if (foundNew) {//if a valid neighbour is already found, this means there are 2 possible paths from the current point
otherPaths.push([x, y]);
} else {
lineGround.push([x / voxels, y / voxels]);
nowChecking = [x, y];
//valid point gets added to the line and currently explored point get updated
foundNew = true;
}
if (x >= voxels) done = true;
}
} else if (i == toCheck.length - 1 && !foundNew) {
if (otherPaths.length > 0) {
nowChecking = otherPaths.pop();
//if none of the neighbours are correct an alternative path gets explored
foundNew = true;
}
}
}
if (!foundNew || looped++ > voxels * 10) {
//if it never found a valid neighbour, or it's looped too often break from the whileloop
console.log('loops: ', looped);
break;
}
}
if (lineGround[0][0] !== 0) lineGround.splice(0, 0, [0, lineGround[0][1]]);
if (lineGround[lineGround.length - 1][0] !== 1) lineGround.push([1, lineGround[lineGround.length - 1][1]]);
//x=0 and x=1 have to exist, so if they don't exist yet, add them
return lineGround;
}
You can also test it here: game. If you click you remove (set to 0) a few voxels within a radius of where you clicked. Also the line gets recalculated.
I'm stuck on this, because I have no idea why the line stops in some situations.
All code is here. The relevant file is js/Level.js

There are more problems than the one you raised. I played a bit on your site and there are many patterns where things go wrong.
I tried to follow the logic of your code, but got lost in details. So I rewrote most of the code. The main idea is that you should keep record of which direction (slope) you are travelling along the ground in order to know in which order you should look among the neighbours for one that is part of the ground.
Let's say the neighbours are numbered as follows, from 0 to 7:
+---+---+---+
| 7 | 0 | 1 |
+---+---+---+
| 6 | * | 2 |
+---+---+---+
| 5 | 4 | 3 |
+---+---+---+
The cell marked with * is the last cell you found to be on ground level. Now let's say the previous one found was at 6, then the search among the neighbours should start at 7, then 0, 1, 2, ... 5. The first one that is found to be solid, should be the next cell added to ground level.
Another example: if the previous one found was at 4 (we're going upward), then the neighbours should be searched starting at 5, then 6, 7, 0, 1, 2 and 3.
The first neighbour that is found to be solid (ground) is the one you want to add to your ground line. This way you will follow every curve, into "caves", upward or downward, left or right.
Of course, things can still go weird if you start on an island. But I did not attempt to solve that particular case.
I've implemented the above idea in the following version of your method:
voxelToLine() {
let voxels = this.voxels.length, x, y, i;
// neighbors' relative coordinates listed in clockwise order
const neighbor = [ [0,-1], [1,-1], [1,0], [1,1], [0,1], [-1,1], [-1,0], [-1,-1] ];
for (y = 0; y < voxels; y++) //sets first coordinate for line.
if (this.voxels[0][y]) break; // found ground, don't look further down
let lineGround = [[0, y / voxels]];
let [curX, curY] = [0, y]; //search starts here
let direction = 0; // upward
let looped = 0;
do {// Continues search until right side is located,
// or it got stuk (max 10*voxelmap width loops)
for (i = 0; i < 8; i++) {//check every neighbour, starting at `direction`
[x, y] = [curX + neighbor[direction][0], curY + neighbor[direction][1]];
// if we found ground, then pick that cell as the next one on the line
if (x>=0 && x<voxels && y>=0 && y<voxels && this.voxels[x][y]) break;
direction = (direction + 1) % 8; // turn clockwise to get next neighbour
}
//if it never found a valid neighbour
if (i === 8) break;
lineGround.push([x / voxels, y / voxels]);
// prepare for next round
[curX, curY] = [x, y];
direction = (direction + 5) % 8;
} while (looped++ <= voxels*10 && curX < voxels - 1);
//x=0 and x=1 have to exist, so if they don't exist yet, add them
if (lineGround[0][0] !== 0) lineGround.splice(0, 0, [0, lineGround[0][1]]);
if (lineGround[lineGround.length - 1][0] !== 1)
lineGround.push([1, lineGround[lineGround.length - 1][1]]);
return lineGround;
}

Looks like it's skipping over the voxel right below the last legitimate ground voxel because it's already been "checked" (added to the checkedVoxels array).
Interestingly, this would prevent your ground path to ever turn 90 degrees (you'll notice your example picture doesn't have such a voxel pattern).

Diamond Square Algorithm fixed size

I am trying to figure out a way to have a fixed scale for the:
https://en.wikipedia.org/wiki/Diamond-square_algorithm
I see that the algorithm requires a power of 2 (+1) size of the array.
The problem I am having is that I would like to have the same heightmap produced regardless of the resolution. So if I have a resolution of 512 it would look the same as with the resolution 256 but just have less detail. I just can't figure out how to do this with.
My initial thought was to always create the heightmap in a certain dimension e.g. 1024 and downsample to the res I would like. Problem is I would like the upper resolution to be quite high (say 4096) and this severely reduces the performance at lower resolutions as we have to run the algo at the highest possible resolution.
Currently the algorithm is in javascript here is a snippet:
function Advanced() {
var adv = {},
res, max, heightmap, roughness;
adv.heightmap = function() {
// heightmap has one extra pixel this is ot remove it.
var hm = create2DArray(res-1, res-1);
for(var x = 0;x< res-1;x++) {
for(var y = 0;y< res-1;y++) {
hm[x][y] = heightmap[x][y];
}
}
return hm;
}
adv.get = function(x,y) {
if (x < 0 || x > max || y < 0 || y > max) return -1;
return heightmap[x][y];
}
adv.set = function(x,y,val) {
if(val < 0) {
val = 0;
}
heightmap[x][y] = val;
}
adv.divide = function(size) {
var x, y, half = size / 2;
var scale = roughness * size;
if (half < 1) return;
for (y = half; y < max; y += size) {
for (x = half; x < max; x += size) {
adv.square(x, y, half, Math.random() * scale * 2 - scale);
}
}
for (y = 0; y <= max; y += half) {
for (x = (y + half) % size; x <= max; x += size) {
adv.diamond(x, y, half, Math.random() * scale * 2 - scale);
}
}
adv.divide(size / 2);
}
adv.average = function(values) {
var valid = values.filter(function(val) {
return val !== -1;
});
var total = valid.reduce(function(sum, val) {
return sum + val;
}, 0);
return total / valid.length;
}
adv.square = function(x, y, size, offset) {
var ave = adv.average([
adv.get(x - size, y - size), // upper left
adv.get(x + size, y - size), // upper right
adv.get(x + size, y + size), // lower right
adv.get(x - size, y + size) // lower left
]);
adv.set(x, y, ave + offset);
}
adv.diamond = function(x, y, size, offset) {
var ave = adv.average([
adv.get(x, y - size), // top
adv.get(x + size, y), // right
adv.get(x, y + size), // bottom
adv.get(x - size, y) // left
]);
adv.set(x, y, Math.abs(ave + offset));
}
adv.generate = function(properties, resolution) {
Math.seedrandom(properties.seed);
res = resolution + 1;
max = res - 1;
heightmap = create2DArray(res, res);
roughness = properties.roughness;
adv.set(0, 0, max);
adv.set(max, 0, max / 2);
adv.set(max, max, 0);
adv.set(0, max, max / 2);
adv.divide(max);
}
function create2DArray(d1, d2) {
var x = new Array(d1),
i = 0,
j = 0;
for (i = 0; i < d1; i += 1) {
x[i] = new Array(d2);
}
for (i=0; i < d1; i += 1) {
for (j = 0; j < d2; j += 1) {
x[i][j] = 0;
}
}
return x;
}
return adv;
}
Anyone ever done this before ?

Not quite sure if I understand your question yet but I'll provide further clarification if I can.
You've described a case where you want a diamond-square heightmap with a resolution of 256 to be used at a size of 512 without scaling it up. I'll go through an example using a 2x2 heightmap to a "size" of 4x4.
A diamond-square heightmap is really a set of vertices rather than tiles or squares, so a heightmap with a size of 2x2 is really a set of 3x3 vertices as shown:
You could either render this using the heights of the corners, or you might turn it into a 2x2 set of squares by taking the average of the four surrounding points - really this is just the "square" step of the algorithm without the displacement step.
So in this case the "height" of the top-left square would be the average of the (0, 0), (0, 1), (1, 1) and (1, 0) points.
If you wanted to draw this at a higher resolution, you could split each square up into a smaller set of 4 squares, adjusting the average based on how close it is to each point.
So now the value of the top-left-most square would be a sample of the 4 sub-points around it or a sample of its position relative to the points around it. But really this is just the diamond square algorithm applied again without any displacement (no roughness) so you may as well apply the algorithm again and go to the larger size.
You've said that going to the size you wish to go to would be too much for the processor to handle, so you may want to go with this sampling approach on the smaller size. An efficient way would be to render the heightmap to a texture and sample from it and the position required.

Properly implemented diamond & square algorithm has the same first N steps regardless of map resolution so the only thing to ensure the same look is use of some specified seed for pseudo random generator.
To make this work you need:
set seed
allocate arrays and set base randomness magnitude
Diamond
Square
lower base randomness magnitude
loop #3 until lowest resolution hit
If you are not lowering the randomness magnitude properly then the lower recursion/iteration layers can override the shape of the result of the upper layers making this not work.
Here see how I do it just add the seed:
Diamond-square algorithm not working
see the line:
r=(r*220)>>8; if (r<2) r=2;
The r is the base randomness magnitude. The way you are lowering it will determine the shape of the result as you can see I am not dividing it by two but multiplying by 220/256 instead so the lower resolution has bigger bumps which suite my needs.
Now if you want to use non 2^x+1 resolutions then choose the closer bigger resolution and then scale down to make this work for them too. The scaling down should be done carefully to preserve them main grid points of the first few recursion/iteration steps or use bi-cubic ...
If you're interested take a look on more up to date generator based on the linked one:
Diamond&Square Island generator

THREE.js sparse planeBufferGeometry

I have a file with sparse elevations. It is based off of gps data. I have been using this data to populate an PlaneBuffer array with elevations.
var vertices = new Float32Array( (grid.NCOL*grid.NROW) * 4 );
for (var i = 0, q = vertices.length; i < q; i++){
vertices[ i*3 + 0 ] = parseInt(i % (grid.NCOL+1)*4);
vertices[ i*3 + 1 ] = parseInt(i / (grid.NCOL+1)*4);
// vertices[ i*3 + 2 ] = null; // makes no difference
}
for (var i = 0, l = grid.NODES.length; i < l; i++) {
var nodeNumber = grid.NODES[i][0];
var elevation= grid.NODES[i][1];
vertices[ nodeNumber*3 + 2 ] = elevation;
}
My problem is that there are nodes that the elevation values are unknown(Vertex array is sparse with elevations) and should be represented by holes/cutouts in the plane. What I end up with is the null elevations being interpreted as 0 not as holes. I have started down the path of using a rawshader, but still not sure that making null values transparent is the correct method.
The below picture shows my issues. The circled area is a high wall that should not be there, because it triangulating to the "null/0" floor. The red-lines area is where we should have a hole.
EDIT:
Maybe this picture will help to. It is from the bottom. The null elevations being set to zero block the view of the plane and cause the edge of the plane to be triangulated to 0 elevation:
Here is what our desktop application displays. Notice the edges of the plane are not triangulated down to zero but instead left sharp?

Plane buffer Geometries take a Float32Array. This array is default set to 0. Using undefined setter allowed me to set the sparse array out of the float32 type. Attempts to set any value to null and NanN did not work.
RTFM:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/null
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Float32Array
final result as expected:

Your use case seems more appropriate for a point cloud with THREE.Points. potree.org/demo/potree_1.3/showcase/ca13.html – WestLangley 14 mins ago
This example helped:
http://threejs.org/examples/#webgl_buffergeometry_points