Monorepo for Aesthetic.Computer
aesthetic.computer
blank: auto-correct face normals to point outward from box center
- Compute box center, then flip any normal that points inward
- Works correctly for both base (y goes +) and lid (y goes -)
- No more wrong-direction normals from inconsistent vertex ordering
- Fixes faces disappearing or back faces showing through
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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system/public/aesthetic.computer/disks/blank.mjs
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system/public/aesthetic.computer/disks/blank.mjs
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const addFaces = (verts3d, proj, color, tag) => {
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const frontFaces = new Set();
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// Compute box center for outward normal correction
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let cx3 = 0, cy3 = 0, cz3 = 0;
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for (const v of verts3d) { cx3 += v[0]; cy3 += v[1]; cz3 += v[2]; }
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cx3 /= verts3d.length; cy3 /= verts3d.length; cz3 /= verts3d.length;
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for (let fi = 0; fi < faceQuads.length; fi++) {
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const [a, b, c, d] = faceQuads[fi];
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// Face center
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const fcx = (verts3d[a][0] + verts3d[b][0] + verts3d[c][0] + verts3d[d][0]) / 4;
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const fcy = (verts3d[a][1] + verts3d[b][1] + verts3d[c][1] + verts3d[d][1]) / 4;
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const fcz = (verts3d[a][2] + verts3d[b][2] + verts3d[c][2] + verts3d[d][2]) / 4;
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// 3D face normal via cross product of two edges
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const e1 = [verts3d[b][0] - verts3d[a][0], verts3d[b][1] - verts3d[a][1], verts3d[b][2] - verts3d[a][2]];
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const e2 = [verts3d[d][0] - verts3d[a][0], verts3d[d][1] - verts3d[a][1], verts3d[d][2] - verts3d[a][2]];
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const nx = e1[1] * e2[2] - e1[2] * e2[1];
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const ny = e1[2] * e2[0] - e1[0] * e2[2];
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const nz = e1[0] * e2[1] - e1[1] * e2[0];
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// Dot with view direction — positive = facing camera
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const e1x = verts3d[b][0] - verts3d[a][0], e1y = verts3d[b][1] - verts3d[a][1], e1z = verts3d[b][2] - verts3d[a][2];
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const e2x = verts3d[d][0] - verts3d[a][0], e2y = verts3d[d][1] - verts3d[a][1], e2z = verts3d[d][2] - verts3d[a][2];
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let nx = e1y * e2z - e1z * e2y;
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let ny = e1z * e2x - e1x * e2z;
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let nz = e1x * e2y - e1y * e2x;
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// Ensure normal points OUTWARD (away from box center)
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const outDot = nx * (fcx - cx3) + ny * (fcy - cy3) + nz * (fcz - cz3);
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if (outDot < 0) { nx = -nx; ny = -ny; nz = -nz; }
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// Dot with view direction — negative = faces camera (opposes view dir)
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const dot = nx * viewDirX + ny * viewDirY + nz * viewDirZ;
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if (dot >= 0) continue; // normal faces away from camera → back-facing
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if (dot >= 0) continue; // faces away from camera → skip
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frontFaces.add(fi);
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const z = (proj[a][2] + proj[b][2] + proj[c][2] + proj[d][2]) / 4;
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drawList.push({ z, type: "face", proj, verts: [a, b, c, d], color, tag });