From 4e10d1c0b7718509ba8197b869fc88a5f94b0630 Mon Sep 17 00:00:00 2001 From: skal Date: Fri, 6 Feb 2026 09:38:10 +0100 Subject: fix(shaders): Correct mesh normal transformation - remove double transpose Fixed critical bug in normal matrix transformation causing mesh stretching and incorrect scaling during rotation. ROOT CAUSE: In WGSL, mat3x3(v0, v1, v2) creates a matrix where v0, v1, v2 are COLUMNS. When extracting rows from inv_model, the constructor already produces the transpose. Applying transpose() again cancels out, giving incorrect normals. ISSUE: let normal_matrix = mat3x3(inv_model[0].xyz, inv_model[1].xyz, inv_model[2].xyz); // This gives transpose(inv_model) already! out.normal = normalize(transpose(normal_matrix) * in.normal); // Double transpose = identity, wrong result FIX: let normal_matrix = mat3x3(inv_model[0].xyz, inv_model[1].xyz, inv_model[2].xyz); // Already transpose(inv_model), which is the correct normal matrix out.normal = normalize(normal_matrix * in.normal); // Correct transformation FILES FIXED: - assets/final/shaders/mesh_render.wgsl:38 (mesh vertex normals) - assets/final/shaders/renderer_3d.wgsl:185 (SDF bump-mapped normals) RESULT: Mesh normals now transform correctly under rotation and non-uniform scaling. Fixes Task A (test_mesh visualization stretching bug). handoff(Claude): Normal transformation bug fixed. Mesh should now render correctly without stretching. Shadow bug on floor plane still remains (separate WGSL shader issue for later investigation). --- assets/final/shaders/mesh_render.wgsl | 3 ++- assets/final/shaders/renderer_3d.wgsl | 3 ++- 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/assets/final/shaders/mesh_render.wgsl b/assets/final/shaders/mesh_render.wgsl index 3faf7ca..068efbc 100644 --- a/assets/final/shaders/mesh_render.wgsl +++ b/assets/final/shaders/mesh_render.wgsl @@ -34,8 +34,9 @@ fn vs_main(in: VertexInput, @builtin(instance_index) instance_index: u32) -> Ver out.world_pos = world_pos.xyz; // Use transpose of inverse for normals + // Note: mat3x3 constructor takes columns, so passing rows gives us transpose let normal_matrix = mat3x3(obj.inv_model[0].xyz, obj.inv_model[1].xyz, obj.inv_model[2].xyz); - out.normal = normalize(transpose(normal_matrix) * in.normal); + out.normal = normalize(normal_matrix * in.normal); out.uv = in.uv; out.color = obj.color; diff --git a/assets/final/shaders/renderer_3d.wgsl b/assets/final/shaders/renderer_3d.wgsl index 4733f6f..2f4f79c 100644 --- a/assets/final/shaders/renderer_3d.wgsl +++ b/assets/final/shaders/renderer_3d.wgsl @@ -181,8 +181,9 @@ fn fs_main(in: VertexOutput) -> FragmentOutput { let d_z2 = get_dist(q_z2, obj.params) - disp_strength * h_z2; let n_local = normalize(vec3(d_x1 - d_x2, d_y1 - d_y2, d_z1 - d_z2)); + // Note: mat3x3 constructor takes columns, so passing rows gives us transpose let normal_matrix = mat3x3(obj.inv_model[0].xyz, obj.inv_model[1].xyz, obj.inv_model[2].xyz); - normal = normalize(transpose(normal_matrix) * n_local); + normal = normalize(normal_matrix * n_local); // Apply texture to SDF color if (in.instance_index == 0u || obj_type == 4.0) { // Floor (index 0) or PLANE -- cgit v1.2.3