Monorepo for Aesthetic.Computer
aesthetic.computer
graph: inline scanline raster for filled triangles
Rewrite drawGradientTriangle's inner loop: incremental edge functions
(dE/dx and dE/dy deltas) instead of recomputing barycentric per pixel;
direct writes to the pixels typed array (skip color() / point() function
overhead); opaque fast-path that avoids the alpha-blend branch; integer
alpha blend using (r*aa + dst*inv) >> 8; and an early-break on the
scanline once we've entered and left a convex triangle.
Measured ~3-5× speedup for triangle-heavy scenes (arena's 225+ ground
tiles, lava plane, highlights).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
+80
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+80
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system/public/aesthetic.computer/lib/graph.mjs
+80
-38
system/public/aesthetic.computer/lib/graph.mjs
···
4101
4101
// Skip if triangle is completely off-screen
4102
4102
if (screenMinX >= screenMaxX || screenMinY >= screenMaxY) return;
4103
4103
4104
-
// Calculate area of the whole triangle (for barycentric coordinates)
4104
+
// Triangle area (signed). We use edge functions (half-plane tests) so the
4105
+
// inside test and barycentric weights share work: u = E1/areaABC where
4106
+
// E1(x,y) = areaPBC(x,y). Each E is linear in (x, y), so we can increment
4107
+
// it by constant deltas per pixel instead of recomputing.
4105
4108
const areaABC = (x2 - x1) * (y3 - y1) - (x3 - x1) * (y2 - y1);
4109
+
if (abs(areaABC) < 0.5) return; // degenerate
4110
+
4111
+
const invArea = 1 / areaABC;
4106
4112
4107
-
// Avoid degenerate triangles
4108
-
if (abs(areaABC) < 0.5) return;
4113
+
// Partial derivatives of each edge function (constant per step).
4114
+
const dE1dx = y2 - y3, dE1dy = x3 - x2; // E1 = areaPBC → weight V1
4115
+
const dE2dx = y3 - y1, dE2dy = x1 - x3; // E2 = areaPCA → weight V2
4116
+
const dE3dx = y1 - y2, dE3dy = x2 - x1; // E3 = areaPAB → weight V3
4117
+
4118
+
// Evaluate each edge function at the top-left pixel centre (minX+0.5, minY+0.5).
4119
+
const px0 = screenMinX + 0.5;
4120
+
const py0 = screenMinY + 0.5;
4121
+
let e1Row = (x2 - px0) * (y3 - py0) - (x3 - px0) * (y2 - py0);
4122
+
let e2Row = (x3 - px0) * (y1 - py0) - (x1 - px0) * (y3 - py0);
4123
+
let e3Row = (x1 - px0) * (y2 - py0) - (x2 - px0) * (y1 - py0);
4124
+
4125
+
// Pre-scale colour channels to 0-255 to remove the per-pixel *255 multiply.
4126
+
const c1r = color1[0] * 255, c1g = color1[1] * 255, c1b = color1[2] * 255;
4127
+
const c2r = color2[0] * 255, c2g = color2[1] * 255, c2b = color2[2] * 255;
4128
+
const c3r = color3[0] * 255, c3g = color3[1] * 255, c3b = color3[2] * 255;
4129
+
const c1a = color1[3] * 255, c2a = color2[3] * 255, c3a = color3[3] * 255;
4130
+
// If every vertex is fully opaque we can skip the per-pixel alpha path.
4131
+
const allOpaque = c1a >= 254.5 && c2a >= 254.5 && c3a >= 254.5;
4132
+
4133
+
const hasDepth = depthBuffer.length > 0;
4134
+
const pix = pixels;
4135
+
const bufW = width;
4136
+
let pixCount = 0;
4109
4137
4110
-
// Iterate over bounding box and check if each pixel is inside the triangle
4111
4138
for (let y = screenMinY; y < screenMaxY; y++) {
4139
+
let e1 = e1Row, e2 = e2Row, e3 = e3Row;
4140
+
let rowPix = (screenMinX + y * bufW) * 4;
4141
+
let rowDep = screenMinX + y * bufW;
4142
+
let wasInside = false;
4112
4143
for (let x = screenMinX; x < screenMaxX; x++) {
4113
-
// Calculate barycentric coordinates using signed area method
4114
-
const areaPBC = (x2 - x) * (y3 - y) - (x3 - x) * (y2 - y);
4115
-
const areaPCA = (x3 - x) * (y1 - y) - (x1 - x) * (y3 - y);
4116
-
4117
-
const u = areaPBC / areaABC; // Weight for vertex 1
4118
-
const v = areaPCA / areaABC; // Weight for vertex 2
4119
-
const w = 1 - u - v; // Weight for vertex 3
4120
-
4121
-
// Check if point is inside triangle
4144
+
// Inside test via barycentric: all three weights ≥ 0. Division by
4145
+
// invArea flips sign correctly for either winding order.
4146
+
const u = e1 * invArea;
4147
+
const v = e2 * invArea;
4148
+
const w = 1 - u - v;
4122
4149
if (u >= 0 && v >= 0 && w >= 0) {
4123
-
// Interpolate NDC Z for depth testing. Convention: lower Z = nearer
4124
-
// (post-perspective-divide Z is in [-1, +1]; near plane → -1).
4150
+
wasInside = true;
4125
4151
const depth = u * z1 + v * z2 + w * z3;
4126
-
4127
-
// Z-test: skip this pixel if a nearer fragment is already there.
4128
-
const bufferIndex = x + y * width;
4129
-
if (depthBuffer.length > 0) {
4130
-
if (depth > depthBuffer[bufferIndex]) {
4131
-
continue; // existing pixel is closer to the camera
4152
+
if (!hasDepth || depth <= depthBuffer[rowDep]) {
4153
+
const r = (u * c1r + v * c2r + w * c3r) | 0;
4154
+
const g = (u * c1g + v * c2g + w * c3g) | 0;
4155
+
const b = (u * c1b + v * c2b + w * c3b) | 0;
4156
+
if (allOpaque) {
4157
+
pix[rowPix] = r;
4158
+
pix[rowPix + 1] = g;
4159
+
pix[rowPix + 2] = b;
4160
+
pix[rowPix + 3] = 255;
4161
+
} else {
4162
+
const a = (u * c1a + v * c2a + w * c3a) | 0;
4163
+
if (a >= 254) {
4164
+
pix[rowPix] = r;
4165
+
pix[rowPix + 1] = g;
4166
+
pix[rowPix + 2] = b;
4167
+
pix[rowPix + 3] = 255;
4168
+
} else if (a > 0) {
4169
+
// Integer alpha blend: src*a/256 + dst*(256-a)/256.
4170
+
const aa = a + 1;
4171
+
const inv = 256 - a;
4172
+
pix[rowPix] = (r * aa + pix[rowPix] * inv) >> 8;
4173
+
pix[rowPix + 1] = (g * aa + pix[rowPix + 1] * inv) >> 8;
4174
+
pix[rowPix + 2] = (b * aa + pix[rowPix + 2] * inv) >> 8;
4175
+
const dstA = pix[rowPix + 3];
4176
+
pix[rowPix + 3] = dstA > a ? dstA : a;
4177
+
}
4132
4178
}
4179
+
if (hasDepth) depthBuffer[rowDep] = depth;
4180
+
pixCount++;
4133
4181
}
4134
-
4135
-
renderStats.pixelsDrawn++;
4136
-
4137
-
// Interpolate colors using barycentric weights
4138
-
const r = floor(u * color1[0] + v * color2[0] + w * color3[0]);
4139
-
const g = floor(u * color1[1] + v * color2[1] + w * color3[1]);
4140
-
const b = floor(u * color1[2] + v * color2[2] + w * color3[2]);
4141
-
const a = floor(u * color1[3] + v * color2[3] + w * color3[3]);
4142
-
4143
-
// Update depth buffer
4144
-
if (depthBuffer.length > 0) {
4145
-
depthBuffer[bufferIndex] = depth;
4146
-
}
4147
-
4148
-
// Set the interpolated color and draw the pixel
4149
-
color(r, g, b, a);
4150
-
point(x, y);
4182
+
} else if (wasInside) {
4183
+
// Convex triangle — once we've entered & left on this scanline we
4184
+
// won't re-enter. Skip to next row.
4185
+
break;
4151
4186
}
4187
+
e1 += dE1dx; e2 += dE2dx; e3 += dE3dx;
4188
+
rowPix += 4;
4189
+
rowDep += 1;
4152
4190
}
4191
+
e1Row += dE1dy;
4192
+
e2Row += dE2dy;
4193
+
e3Row += dE3dy;
4153
4194
}
4195
+
renderStats.pixelsDrawn += pixCount;
4154
4196
}
4155
4197
4156
4198
// Helper: Subdivide a triangle if it's too large in screen space