From a109983c194c45ad85f0e481232bc605c7cfd85b Mon Sep 17 00:00:00 2001
From: skal <pascal.massimino@gmail.com>
Date: Fri, 13 Feb 2026 08:34:24 +0100
Subject: Remediation: Implement shared common/shaders/ directory

Eliminates 36 duplicate shader files across workspaces.

Structure:
- common/shaders/{math,render,compute}/ - Shared utilities (20 files)
- workspaces/*/shaders/ - Workspace-specific only

Changes:
- Created common/shaders/ with math, render, compute subdirectories
- Moved 20 common shaders from workspaces to common/
- Removed duplicates from test workspace
- Updated assets.txt: ../../common/shaders/ references
- Enhanced asset_packer.cc: filesystem path normalization for ../ resolution

Implementation: Option 1 from SHADER_REUSE_INVESTIGATION.md
- Single source of truth for common code
- Workspace references via relative paths
- Path normalization in asset packer

handoff(Claude): Common shader directory implemented
---
 common/shaders/ray_triangle.wgsl | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 common/shaders/ray_triangle.wgsl

(limited to 'common/shaders/ray_triangle.wgsl')

diff --git a/common/shaders/ray_triangle.wgsl b/common/shaders/ray_triangle.wgsl
new file mode 100644
index 0000000..13341c8
--- /dev/null
+++ b/common/shaders/ray_triangle.wgsl
@@ -0,0 +1,30 @@
+// This file is part of the 64k demo project.
+// Möller-Trumbore ray-triangle intersection algorithm.
+// Reference: "Fast, Minimum Storage Ray-Triangle Intersection"
+
+struct TriangleHit {
+  uv: vec2<f32>,
+  z: f32,
+  N: vec3<f32>,
+  hit: bool,
+};
+
+fn ray_triangle_intersection(
+  orig: vec3<f32>,
+  dir: vec3<f32>,
+  p0: vec3<f32>,
+  p1: vec3<f32>,
+  p2: vec3<f32>
+) -> TriangleHit {
+  let d10 = p1 - p0;
+  let d20 = p2 - p0;
+  let N = cross(d10, d20);
+  let det = -dot(dir, N);
+  let invdet = 1.0 / det;
+  let d0 = orig - p0;
+  let nd = cross(d0, dir);
+  let uv = vec2<f32>(dot(d20, nd), -dot(d10, nd)) * invdet;
+  let z = dot(d0, N) * invdet;
+  let hit = det > 0.0 && z >= 0.0 && uv.x >= 0.0 && uv.y >= 0.0 && (uv.x + uv.y) < 1.0;
+  return TriangleHit(uv, z, N, hit);
+}
-- 
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