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ehaliewicz/barycentric.html

Created November 12, 2024 21:40
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barycentric.html
<!DOCTYPE html>
<html>
<head></head>
<body>
<canvas id="canvas-id" style="image-rendering:pixelated;"></canvas>
<script type="text/javascript">
// triangles are
// [[x,y,z],[x,y,z],[x,y,z]]
(function() {
const getDeterminant = function(ax, ay, bx, by, cx, cy) {
//const ab = new Vector(b);
//ab.sub(a);
const abx = bx - ax;
const aby = by - ay;
const acx = cx - ax;
const acy = cy - ay;
//const ac = new Vector(c);
//ac.sub(a);
//return ab[1] * ac[0] - ab[0] * ac[1];
return aby * acx - abx * acy;
}
const isTopLeft = function(start, end) {
const edgex = end[0] - start[0];
const edgey = end[1] - start[1];
const isLeftEdge = edgey > 0;
const isTopEdge = edgey == 0 && edgex < 0;
return isLeftEdge || isTopEdge;
}
const canvas = document.getElementById("canvas-id");
console.log("canvas: ", canvas);
const devicePixelRatio = 0.5;
const bufWidth = window.innerWidth * devicePixelRatio;
const bufHeight = window.innerHeight * devicePixelRatio;
canvas.width = bufWidth;
canvas.height = bufHeight;
canvas.style.width = window.innerWidth + "px";
canvas.style.height = window.innerHeight + "px";
const ctx = canvas.getContext("2d");
const screenBuffer = ctx.createImageData(window.innerWidth * devicePixelRatio, window.innerHeight * devicePixelRatio);
const blocksize = 8;
var canvasWBlocks = Math.floor((screenBuffer.Width + blocksize-1) / blocksize);
var canvasHBlocks = Math.floor((screenBuffer.Height + blocksize-1) / blocksize);
var block_full = new Uint8Array(canvasWBlocks * canvasHBlocks);
let pixels = 0;
function drawTriangle( x1, y1, x2, y2, x3, y3, col32, data, width, height) {
// http://devmaster.net/forums/topic/1145-advanced-rasterization/
// 28.4 fixed-point coordinates
var x1 = Math.round( 16 * x1 );
var x2 = Math.round( 16 * x2 );
var x3 = Math.round( 16 * x3 );
var y1 = Math.round( 16 * y1 );
var y2 = Math.round( 16 * y2 );
var y3 = Math.round( 16 * y3 );
// Deltas
var dx12 = x1 - x2, dy12 = y2 - y1;
var dx23 = x2 - x3, dy23 = y3 - y2;
var dx31 = x3 - x1, dy31 = y1 - y3;
// Bounding rectangle
var minx = Math.max( ( Math.min( x1, x2, x3 ) + 0xf ) >> 4, 0 );
var maxx = Math.min( ( Math.max( x1, x2, x3 ) + 0xf ) >> 4, width );
var miny = Math.max( ( Math.min( y1, y2, y3 ) + 0xf ) >> 4, 0 );
var maxy = Math.min( ( Math.max( y1, y2, y3 ) + 0xf ) >> 4, height );
// Block size, standard 8x8 (must be power of two)
var q = blocksize;
// Start in corner of 8x8 block
minx &= ~(q - 1);
miny &= ~(q - 1);
// Constant part of half-edge functions
var c1 = dy12 * ((minx << 4) - x1) + dx12 * ((miny << 4) - y1);
var c2 = dy23 * ((minx << 4) - x2) + dx23 * ((miny << 4) - y2);
var c3 = dy31 * ((minx << 4) - x3) + dx31 * ((miny << 4) - y3);
// Correct for fill convention
if ( dy12 > 0 || ( dy12 == 0 && dx12 > 0 ) ) c1 ++;
if ( dy23 > 0 || ( dy23 == 0 && dx23 > 0 ) ) c2 ++;
if ( dy31 > 0 || ( dy31 == 0 && dx31 > 0 ) ) c3 ++;
// Note this doesn't kill subpixel precision, but only because we test for >=0 (not >0).
// It's a bit subtle.
c1 = (c1 - 1) >> 4;
c2 = (c2 - 1) >> 4;
c3 = (c3 - 1) >> 4;
// Set up min/max corners
var qm1 = q - 1; // for convenience
var nmin1 = 0, nmax1 = 0;
var nmin2 = 0, nmax2 = 0;
var nmin3 = 0, nmax3 = 0;
if (dx12 >= 0) nmax1 -= qm1*dx12; else nmin1 -= qm1*dx12;
if (dy12 >= 0) nmax1 -= qm1*dy12; else nmin1 -= qm1*dy12;
if (dx23 >= 0) nmax2 -= qm1*dx23; else nmin2 -= qm1*dx23;
if (dy23 >= 0) nmax2 -= qm1*dy23; else nmin2 -= qm1*dy23;
if (dx31 >= 0) nmax3 -= qm1*dx31; else nmin3 -= qm1*dx31;
if (dy31 >= 0) nmax3 -= qm1*dy31; else nmin3 -= qm1*dy31;
// Loop through blocks
var linestep = (width - q);// * 4;
var scale = 255.0 / (c1 + c2 + c3);
var cb1 = c1;
var cb2 = c2;
var cb3 = c3;
var qstep = -q;
var e1x = qstep * dy12;
var e2x = qstep * dy23;
var e3x = qstep * dy31;
var x0 = minx;
for (var y0 = miny; y0 < maxy; y0 += q) {
// New block line - keep hunting for tri outer edge in old block line dir
while (x0 >= minx && x0 < maxx && cb1 >= nmax1 && cb2 >= nmax2 && cb3 >= nmax3) {
x0 += qstep;
cb1 += e1x;
cb2 += e2x;
cb3 += e3x;
}
// Okay, we're now in a block we know is outside. Reverse direction and go into main loop.
qstep = -qstep;
e1x = -e1x;
e2x = -e2x;
e3x = -e3x;
while (1) {
// Step everything
x0 += qstep;
cb1 += e1x;
cb2 += e2x;
cb3 += e3x;
// We're done with this block line when at least one edge completely out
// If an edge function is too small and decreasing in the current traversal
// dir, we're done with this line.
if (x0 < minx || x0 >= maxx) break;
if (cb1 < nmax1) if (e1x < 0) break; else continue;
if (cb2 < nmax2) if (e2x < 0) break; else continue;
if (cb3 < nmax3) if (e3x < 0) break; else continue;
// We can skip this block if its already fully covered
var blockX = (x0 / q) | 0;
var blockY = (y0 / q) | 0;
var blockInd = blockX + blockY * canvasWBlocks;
if (block_full[blockInd]) continue;
// Offset at top-left corner
var offset = (x0 + y0 * width);
// Accept whole block when fully covered
if (cb1 >= nmin1 && cb2 >= nmin2 && cb3 >= nmin3) {
var cy1 = cb1;
var cy2 = cb2;
for ( var iy = 0; iy < q; iy ++ ) {
//var cx1 = cy1;
//var cx2 = cy2;
for ( var ix = 0; ix < q; ix ++ ) {
//var u = cx1 * scale; // 0-255!
//var v = cx2 * scale; // 0-255!
data[offset] = col32;
//pixels++;
//data[offset] = (u<<24)|(v<<16)|0xFF;
//cx1 += dy12;
//cx2 += dy23;
offset++;
}
pixels += (q*q);
//cy1 += dx12;
//cy2 += dx23;
offset += linestep;
}
block_full[blockInd] = 1;
} else { // Partially covered block
var cy1 = cb1;
var cy2 = cb2;
var cy3 = cb3;
for ( var iy = 0; iy < q; iy ++ ) {
var cx1 = cy1;
var cx2 = cy2;
var cx3 = cy3;
for ( var ix = 0; ix < q; ix ++ ) {
if ( (cx1 | cx2 | cx3) >= 0) {
//var u = cx1 * scale; // 0-255!
//var v = cx2 * scale; // 0-255!
data[offset] = col32;
//data[offset] = (u<<24)|(v<<16)|0xFF;
pixels++;
}
cx1 += dy12;
cx2 += dy23;
cx3 += dy31;
offset++;
}
cy1 += dx12;
cy2 += dx23;
cy3 += dx31;
offset += linestep;
}
}
}
// Advance to next row of blocks
cb1 += q*dx12;
cb2 += q*dx23;
cb3 += q*dx31;
}
}
const drawTris = function(numTris, tris, verts, buffer, bufWidth, bufHeight) {
for(let i = 0; i < numTris; i += 4) {
const vai = tris[i+0];
const vbi = tris[i+1];
const vci = tris[i+2];
const col = tris[i+3];
const vax = verts[vai*3+0];
const vay = verts[vai*3+1];
//const vax = verts[vai*3+0];
const vbx = verts[vbi*3+0];
const vby = verts[vbi*3+1];
const vcx = verts[vci*3+0];
const vcy = verts[vci*3+1];
drawTriangle( vax, vay, vbx, vby, vcx, vcy, col, buffer, bufWidth, bufHeight);
}
}
const buf = new ArrayBuffer(screenBuffer.data.length);
const buf8 = new Uint8ClampedArray(buf);
const data = new Uint32Array(buf);
const vertices = new Uint32Array(3*10000);
let numTris = 0;
let numVerts = 0;
let vertIdx = 0;
let triIdx = 0;
vertices[vertIdx++] = 140;
vertices[vertIdx++] = 100;
vertices[vertIdx++] = 0;
vertices[vertIdx++] = 140;
vertices[vertIdx++] = 40;
vertices[vertIdx++] = 0;
vertices[vertIdx++] = 80;
vertices[vertIdx++] = 40;
vertices[vertIdx++] = 0;
vertices[vertIdx++] = 50;
vertices[vertIdx++] = 90;
vertices[vertIdx++] = 0;
numVerts = 4;
const tris = new Uint32Array(4*10000);
//[
0,1,2, ((0xFF<<24)|(120<<16)|(240<<8)|100), // vertex indexes, plus color attributes
0,2,3, ((0xFF<<24)|(100<<16)|(180<<8)|240)
//];
tris[triIdx++] = 0;
tris[triIdx++] = 1;
tris[triIdx++] = 2;
tris[triIdx++] = ((0xFF<<24)|(120<<16)|(240<<8)|100);
tris[triIdx++] = 0;
tris[triIdx++] = 2;
tris[triIdx++] = 3;
tris[triIdx++] = ((0xFF<<24)|(100<<16)|(180<<8)|240);
numTris = 2;
for(let i = 0; i < 998; i++) {
// last slot is angle, not used yet
const v1 = [Math.floor(Math.random() * bufWidth), Math.floor(Math.random() * bufHeight), 0];
const v2 = [Math.floor(Math.random() * bufWidth), Math.floor(Math.random() * bufHeight), 0];
const v3 = [Math.floor(Math.random() * bufWidth), Math.floor(Math.random() * bufHeight), 0];
const points = [v1,v2,v3];
const center = points.reduce((acc, [ x, y ]) => {
acc[0] += x / points.length;
acc[1] += y / points.length;
return acc;
}, [ 0, 0 ]);
const angles = points.map(([ x, y ]) => {
return [ x, y, Math.atan2(y - center[1], x - center[0]) * 180 / Math.PI ];
});
const pointsSorted = angles.sort((a, b) => b[2] - a[2]);
//const ccwPoints = points.reverse();
//ccwPoints.unshift(ccwPoints.pop());
const r = Math.floor(Math.random() * 255);
const g = Math.floor(Math.random() * 255);
const b = Math.floor(Math.random() * 255);
tris[triIdx++] = numVerts++;
tris[triIdx++] = numVerts++;
tris[triIdx++] = numVerts++;
tris[triIdx++] = ((0xFF<<24)|(r<<16)|(g<<8)|b);
vertices[vertIdx++] = pointsSorted[0][0];
vertices[vertIdx++] = pointsSorted[0][1];
vertices[vertIdx++] = pointsSorted[0][2];
vertices[vertIdx++] = pointsSorted[1][0];
vertices[vertIdx++] = pointsSorted[1][1];
vertices[vertIdx++] = pointsSorted[1][2];
vertices[vertIdx++] = pointsSorted[2][0];
vertices[vertIdx++] = pointsSorted[2][1];
vertices[vertIdx++] = pointsSorted[2][2];
numTris++;
}
console.log(numTris);
console.log(numVerts);
console.log(tris);
console.log(vertices);
const startTime = performance.now();
drawTris(numTris, tris, vertices, data, screenBuffer.width, screenBuffer.height);
//screenBuffer.data.set(data);
screenBuffer.data.set(buf8);
const endTime = performance.now();
console.log("pixels filled: ", pixels);
console.log("" + endTime-startTime, "ms");
const fps = 1000 / (endTime-startTime);
const pixPerSec = pixels * fps;
console.log("" + Math.round(pixPerSec/1000000) + "MPix per second");
ctx.putImageData(screenBuffer, 0, 0);
})();
</script>
</body>
</html>
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