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feat(editor): add --smooth-mesh-normals for area-weighted normal recompute

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Recomputes per-vertex normals as the area-weighted average of
incident face normals. The cross-product magnitude is twice the
triangle area, so larger faces contribute more to the local
direction — gives a clean smooth-shaded result on curved surfaces.

Use cases:
- Imported geometry has no normals (--import-obj leaves them zero
  or face-flat).
- Custom transforms have desynced normals from positions.
- Faceted-by-construction meshes (cube, stairs) need a smooth
  re-shade for stylistic reasons.

Degenerate verts (unreferenced or with sum that cancels to zero —
e.g., the two poles of a UV sphere) fall back to (0,1,0) rather
than leaving NaN; reported separately so the user sees how many.

Verified: sphere → 219 of 221 normalized + 2 degenerate poles
handled cleanly; minimal triangle → 3/3 normalized. Brings command
count to 229 (kArgRequired 210).
This commit is contained in:
Kelsi 2026-05-07 08:33:20 -07:00
parent b38dec7a83
commit d54440a75b
1 changed files with 84 additions and 0 deletions
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84
tools/editor/main.cpp
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@ -561,6 +561,8 @@ static void printUsage(const char* argv0) {
std::printf(" Invert every vertex normal (use for inside-out meshes or two-sided pre-flip)\n");
std::printf(" --mirror-mesh <wom-base> <x|y|z>\n");
std::printf(" Mirror every vertex + normal across the chosen axis (also flips winding)\n");
std::printf(" --smooth-mesh-normals <wom-base>\n");
std::printf(" Recompute per-vertex normals as area-weighted averages of incident face normals\n");
std::printf(" --merge-meshes <a-base> <b-base> <out-base>\n");
std::printf(" Combine two WOMs into one (vertex/index buffers concatenated, batches preserved)\n");
std::printf(" --add-item <zoneDir> <name> [id] [quality] [displayId] [itemLevel]\n");
@ -986,6 +988,7 @@ int main(int argc, char* argv[]) {
"--scale-mesh", "--translate-mesh", "--strip-mesh",
"--gen-texture-noise", "--rotate-mesh",
"--center-mesh", "--flip-mesh-normals", "--mirror-mesh",
"--smooth-mesh-normals",
"--merge-meshes",
"--gen-texture-radial", "--gen-texture-stripes",
"--validate-glb", "--info-glb", "--info-glb-tree", "--info-glb-bytes",
@ -17189,6 +17192,87 @@ int main(int argc, char* argv[]) {
wom.boundMin.x, wom.boundMin.y, wom.boundMin.z,
wom.boundMax.x, wom.boundMax.y, wom.boundMax.z);
return 0;
} else if (std::strcmp(argv[i], "--smooth-mesh-normals") == 0 && i + 1 < argc) {
// Recompute per-vertex normals as the area-weighted
// average of incident face normals. Useful when:
// - Imported geometry has no normals (--import-obj
// leaves them zero or face-flat).
// - Custom transforms have desynced normals from the
// positions (e.g., user post-processed the WOM
// externally).
// - Faceted-by-construction meshes (cube, stairs) need
// a smooth re-shade for stylistic reasons.
//
// The cross-product magnitude is twice the triangle area,
// which weights large faces more — bigger triangles
// contribute more to the local surface direction.
std::string womBase = argv[++i];
if (womBase.size() >= 4 &&
womBase.substr(womBase.size() - 4) == ".wom") {
womBase = womBase.substr(0, womBase.size() - 4);
}
if (!wowee::pipeline::WoweeModelLoader::exists(womBase)) {
std::fprintf(stderr,
"smooth-mesh-normals: %s.wom does not exist\n",
womBase.c_str());
return 1;
}
auto wom = wowee::pipeline::WoweeModelLoader::load(womBase);
if (!wom.isValid()) {
std::fprintf(stderr,
"smooth-mesh-normals: failed to load %s.wom\n",
womBase.c_str());
return 1;
}
// Reset vertex normals to zero so the accumulator sums
// cleanly.
for (auto& v : wom.vertices) v.normal = glm::vec3(0);
for (size_t k = 0; k + 2 < wom.indices.size(); k += 3) {
uint32_t i0 = wom.indices[k];
uint32_t i1 = wom.indices[k + 1];
uint32_t i2 = wom.indices[k + 2];
if (i0 >= wom.vertices.size() ||
i1 >= wom.vertices.size() ||
i2 >= wom.vertices.size()) continue;
glm::vec3 p0 = wom.vertices[i0].position;
glm::vec3 p1 = wom.vertices[i1].position;
glm::vec3 p2 = wom.vertices[i2].position;
// Cross product magnitude == 2 * triangle area, used
// as the weight.
glm::vec3 faceN = glm::cross(p1 - p0, p2 - p0);
wom.vertices[i0].normal += faceN;
wom.vertices[i1].normal += faceN;
wom.vertices[i2].normal += faceN;
}
int normalized = 0, degenerate = 0;
for (auto& v : wom.vertices) {
float len = glm::length(v.normal);
if (len > 1e-6f) {
v.normal /= len;
normalized++;
} else {
// Vertex unreferenced or sum cancelled — fall
// back to "up" rather than leaving zero so the
// shader doesn't get a dark NaN spot.
v.normal = glm::vec3(0, 1, 0);
degenerate++;
}
}
if (!wowee::pipeline::WoweeModelLoader::save(wom, womBase)) {
std::fprintf(stderr,
"smooth-mesh-normals: failed to save %s.wom\n",
womBase.c_str());
return 1;
}
std::printf("Smoothed normals on %s.wom\n", womBase.c_str());
std::printf(" vertices touched : %zu\n", wom.vertices.size());
std::printf(" triangles read : %zu\n", wom.indices.size() / 3);
std::printf(" normalized : %d\n", normalized);
if (degenerate > 0) {
std::printf(" degenerate : %d (set to (0,1,0))\n",
degenerate);
}
return 0;
} else if (std::strcmp(argv[i], "--merge-meshes") == 0 && i + 3 < argc) {
// Combine two WOMs into one. The second mesh's indices
// are offset by the first mesh's vertex count, and its