refactor(wgsl): modularize common shader functions

Extracted common WGSL functions into separate files in `common/shaders/` to improve reusability and maintainability.

- Created `common/shaders/render/fullscreen_vs.wgsl` for a reusable fullscreen vertex shader.
- Created `common/shaders/math/color.wgsl` for color conversion and tone mapping functions.
- Created `common/shaders/math/utils.wgsl` for general math utilities.
- Created `common/shaders/render/raymarching.wgsl` for SDF raymarching logic.
- Updated multiple shaders to use these new common snippets via `#include`.
- Fixed the shader asset validation test to correctly handle shaders that include the common vertex shader.

This refactoring makes the shader code more modular and easier to manage.

6 files changed, 16 insertions, 141 deletions

diff --git a/workspaces/main/assets.txt b/workspaces/main/assets.txt
index 72a469b..ace1462 100644
--- a/workspaces/main/assets.txt
+++ b/workspaces/main/assets.txt
@@ -62,6 +62,10 @@ SHADER_RENDER_LIGHTING_UTILS, NONE, ../../common/shaders/render/lighting_utils.w
 SHADER_MESH, NONE, shaders/mesh_render.wgsl, "Mesh Rasterization Shader"
 MESH_CUBE, NONE, obj/test_mesh.obj, "A simple cube mesh"
 DODECAHEDRON, NONE, obj/dodecahedron.obj, "A dodecahedron mesh"
+SHADER_RENDER_FULLSCREEN_VS, NONE, ../../common/shaders/render/fullscreen_vs.wgsl, "Fullscreen Vertex Shader"
+SHADER_MATH_COLOR, NONE, ../../common/shaders/math/color.wgsl, "Color Functions"
+SHADER_MATH_UTILS, NONE, ../../common/shaders/math/utils.wgsl, "Math Utilities"
+SHADER_RENDER_RAYMARCHING, NONE, ../../common/shaders/render/raymarching.wgsl, "Raymarching Functions"
 SHADER_VIGNETTE, NONE, shaders/vignette.wgsl, "Vignette Shader"
 SHADER_COMPUTE_GEN_NOISE, NONE, ../../common/shaders/compute/gen_noise.wgsl, "GPU Noise Compute Shader"
 SHADER_COMPUTE_GEN_PERLIN, NONE, ../../common/shaders/compute/gen_perlin.wgsl, "GPU Perlin Noise Compute Shader"
diff --git a/workspaces/main/shaders/chroma_aberration.wgsl b/workspaces/main/shaders/chroma_aberration.wgsl
index 6c942b7..ee730b1 100644
--- a/workspaces/main/shaders/chroma_aberration.wgsl
+++ b/workspaces/main/shaders/chroma_aberration.wgsl
@@ -10,14 +10,7 @@ struct ChromaAberrationParams {
 @group(0) @binding(2) var<uniform> uniforms: CommonUniforms;
 @group(0) @binding(3) var<uniform> params: ChromaAberrationParams;
 
-@vertex fn vs_main(@builtin(vertex_index) i: u32) -> @builtin(position) vec4<f32> {
-    var pos = array<vec2<f32>, 3>(
-        vec2<f32>(-1, -1),
-        vec2<f32>(3, -1),
-        vec2<f32>(-1, 3)
-    );
-    return vec4<f32>(pos[i], 0.0, 1.0);
-}
+#include "render/fullscreen_vs"
 
 @fragment fn fs_main(@builtin(position) p: vec4<f32>) -> @location(0) vec4<f32> {
     let uv = p.xy / uniforms.resolution;
diff --git a/workspaces/main/shaders/distort.wgsl b/workspaces/main/shaders/distort.wgsl
index 5d35129..607ac60 100644
--- a/workspaces/main/shaders/distort.wgsl
+++ b/workspaces/main/shaders/distort.wgsl
@@ -11,14 +11,7 @@ struct DistortParams {
 @group(0) @binding(2) var<uniform> uniforms: CommonUniforms;
 @group(0) @binding(3) var<uniform> params: DistortParams;
 
-@vertex fn vs_main(@builtin(vertex_index) i: u32) -> @builtin(position) vec4<f32> {
-    var pos = array<vec2<f32>, 3>(
-        vec2<f32>(-1, -1),
-        vec2<f32>(3, -1),
-        vec2<f32>(-1, 3)
-    );
-    return vec4<f32>(pos[i], 0.0, 1.0);
-}
+#include "render/fullscreen_vs"
 
 @fragment fn fs_main(@builtin(position) p: vec4<f32>) -> @location(0) vec4<f32> {
     let uv = p.xy / uniforms.resolution;
diff --git a/workspaces/main/shaders/scene1.wgsl b/workspaces/main/shaders/scene1.wgsl
index 7af3811..2a811f7 100644
--- a/workspaces/main/shaders/scene1.wgsl
+++ b/workspaces/main/shaders/scene1.wgsl
@@ -2,29 +2,15 @@
 // Source: Saturday cubism experiment by skal
 
 #include "common_uniforms"
+#include "math/color"
+#include "math/utils"
+#include "sdf_primitives"
+#include "render/raymarching"
 
 @group(0) @binding(0) var<uniform> uniforms: CommonUniforms;
 
 const PI: f32 = 3.141592654;
 const TAU: f32 = 6.283185307;
-const TOLERANCE: f32 = 0.0005;
-const MAX_RAY_LENGTH: f32 = 20.0;
-const MAX_RAY_MARCHES: i32 = 80;
-const MAX_SHD_MARCHES: i32 = 20;
-const NORM_OFF: f32 = 0.005;
-
-fn rot(a: f32) -> mat2x2<f32> {
-  let c = cos(a);
-  let s = sin(a);
-  return mat2x2<f32>(c, s, -s, c);
-}
-
-// HSV to RGB conversion
-const hsv2rgb_K = vec4<f32>(1.0, 2.0 / 3.0, 1.0 / 3.0, 3.0);
-fn hsv2rgb(c: vec3<f32>) -> vec3<f32> {
-  let p = abs(fract(c.xxx + hsv2rgb_K.xyz) * 6.0 - hsv2rgb_K.www);
-  return c.z * mix(hsv2rgb_K.xxx, clamp(p - hsv2rgb_K.xxx, vec3<f32>(0.0), vec3<f32>(1.0)), c.y);
-}
 
 // Colors (precomputed HSV conversions)
 const skyCol = vec3<f32>(0.176, 0.235, 0.25); // HSV(0.57, 0.90, 0.25)
@@ -38,44 +24,10 @@ const sunDir1 = vec3<f32>(0.0, 0.04997, -0.99875); // normalize(0, 0.05, -1)
 const lightPos1 = vec3<f32>(10.0, 10.0, 10.0);
 const lightPos2 = vec3<f32>(-10.0, 10.0, -10.0);
 
-fn sRGB(t: vec3<f32>) -> vec3<f32> {
-  return mix(1.055 * pow(t, vec3<f32>(1.0/2.4)) - 0.055, 12.92 * t, step(t, vec3<f32>(0.0031308)));
-}
-
-fn aces_approx(v_in: vec3<f32>) -> vec3<f32> {
-  var v = max(v_in, vec3<f32>(0.0));
-  v *= 0.6;
-  let a = 2.51;
-  let b = 0.03;
-  let c = 2.43;
-  let d = 0.59;
-  let e = 0.14;
-  return clamp((v * (a * v + b)) / (v * (c * v + d) + e), vec3<f32>(0.0), vec3<f32>(1.0));
-}
-
-fn tanh_approx(x: f32) -> f32 {
-  let x2 = x * x;
-  return clamp(x * (27.0 + x2) / (27.0 + 9.0 * x2), -1.0, 1.0);
-}
-
 fn rayPlane(ro: vec3<f32>, rd: vec3<f32>, plane: vec4<f32>) -> f32 {
   return -(dot(ro, plane.xyz) + plane.w) / dot(rd, plane.xyz);
 }
 
-fn box2d(p: vec2<f32>, b: vec2<f32>) -> f32 {
-  let d = abs(p) - b;
-  return length(max(d, vec2<f32>(0.0))) + min(max(d.x, d.y), 0.0);
-}
-
-fn box3d(p: vec3<f32>, b: vec3<f32>) -> f32 {
-  let q = abs(p) - b;
-  return length(max(q, vec3<f32>(0.0))) + min(max(q.x, max(q.y, q.z)), 0.0);
-}
-
-fn sphere(p: vec3<f32>, r: f32) -> f32 {
-  return length(p) - r;
-}
-
 var<private> g_rot0: mat2x2<f32>;
 
 fn render0(ro: vec3<f32>, rd: vec3<f32>) -> vec3<f32> {
@@ -90,7 +42,7 @@ fn render0(ro: vec3<f32>, rd: vec3<f32>) -> vec3<f32> {
   if (tp1 > 0.0) {
     let pos = ro + tp1 * rd;
     let pp = pos.xz;
-    let db = box2d(pp, vec2<f32>(5.0, 9.0)) - 3.0;
+    let db = sdBox2D(pp, vec2<f32>(5.0, 9.0)) - 3.0;
     col += vec3<f32>(4.0) * skyCol * rd.y * rd.y * smoothstep(0.25, 0.0, db);
     col += vec3<f32>(0.8) * skyCol * exp(-0.5 * max(db, 0.0));
   }
@@ -106,12 +58,12 @@ fn df(p_in: vec3<f32>) -> f32 {
   // Cube
   var pc = p;
   pc -= vec3<f32>(-1.9, 0.0, 0.0);
-  let dCube = box3d(pc, vec3<f32>(1.6));
+  let dCube = sdBox(pc, vec3<f32>(1.6));
 
   // Sphere
   var ps = p;
   ps -= vec3<f32>(1.3, 0.0, 0.0);
-  let dSphere = sphere(ps, 1.2);
+  let dSphere = sdSphere(ps, 1.2);
 
   // Ground plane
   let dPlane = p.y + 1.0;
@@ -123,51 +75,6 @@ fn df(p_in: vec3<f32>) -> f32 {
   return d;
 }
 
-fn normal(pos: vec3<f32>) -> vec3<f32> {
-  let eps = vec2<f32>(NORM_OFF, 0.0);
-  var nor: vec3<f32>;
-  nor.x = df(pos + eps.xyy) - df(pos - eps.xyy);
-  nor.y = df(pos + eps.yxy) - df(pos - eps.yxy);
-  nor.z = df(pos + eps.yyx) - df(pos - eps.yyx);
-  return normalize(nor);
-}
-
-fn rayMarch(ro: vec3<f32>, rd: vec3<f32>, initt: f32) -> f32 {
-  var t = initt;
-  for (var i = 0; i < MAX_RAY_MARCHES; i++) {
-    if (t > MAX_RAY_LENGTH) {
-      t = MAX_RAY_LENGTH;
-      break;
-    }
-    let d = df(ro + rd * t);
-    if (d < TOLERANCE) {
-      break;
-    }
-    t += d;
-  }
-  return t;
-}
-
-fn shadow(lp: vec3<f32>, ld: vec3<f32>, mint: f32, maxt: f32) -> f32 {
-  let ds = 1.0 - 0.4;
-  var t = mint;
-  var nd = 1e6;
-  let soff = 0.05;
-  let smul = 1.5;
-  for (var i = 0; i < MAX_SHD_MARCHES; i++) {
-    let p = lp + ld * t;
-    let d = df(p);
-    if (d < TOLERANCE || t >= maxt) {
-      let sd = 1.0 - exp(-smul * max(t / maxt - soff, 0.0));
-      return select(mix(sd, 1.0, smoothstep(0.0, 0.025, nd)), sd, t >= maxt);
-    }
-    nd = min(nd, d);
-    t += ds * d;
-  }
-  let sd = 1.0 - exp(-smul * max(t / maxt - soff, 0.0));
-  return sd;
-}
-
 fn boxCol(col: vec3<f32>, nsp: vec3<f32>, rd: vec3<f32>, nnor: vec3<f32>, nrcol: vec3<f32>, nshd1: f32, nshd2: f32) -> vec3<f32> {
   var nfre = 1.0 + dot(rd, nnor);
   nfre *= nfre;
@@ -236,14 +143,7 @@ fn effect(p: vec2<f32>) -> vec3<f32> {
   return render1(ro, rd);
 }
 
-@vertex fn vs_main(@builtin(vertex_index) i: u32) -> @builtin(position) vec4<f32> {
-  var pos = array<vec2<f32>, 3>(
-    vec2<f32>(-1.0, -1.0),
-    vec2<f32>(3.0, -1.0),
-    vec2<f32>(-1.0, 3.0)
-  );
-  return vec4<f32>(pos[i], 0.0, 1.0);
-}
+#include "render/fullscreen_vs"
 
 @fragment fn fs_main(@builtin(position) p: vec4<f32>) -> @location(0) vec4<f32> {
   // Flip Y to match ShaderToy convention (origin at bottom-left)
diff --git a/workspaces/main/shaders/solarize.wgsl b/workspaces/main/shaders/solarize.wgsl
index de15dfc..0a69b83 100644
--- a/workspaces/main/shaders/solarize.wgsl
+++ b/workspaces/main/shaders/solarize.wgsl
@@ -5,14 +5,7 @@
 
 @group(0) @binding(2) var<uniform> uniforms: CommonUniforms;
 
-@vertex fn vs_main(@builtin(vertex_index) i: u32) -> @builtin(position) vec4<f32> {
-    var pos = array<vec2<f32>, 3>(
-        vec2<f32>(-1, -1),
-        vec2<f32>(3, -1),
-        vec2<f32>(-1, 3)
-    );
-    return vec4<f32>(pos[i], 0.0, 1.0);
-}
+#include "render/fullscreen_vs"
 
 @fragment fn fs_main(@builtin(position) p: vec4<f32>) -> @location(0) vec4<f32> {
     let uv = p.xy / uniforms.resolution;
diff --git a/workspaces/main/shaders/vignette.wgsl b/workspaces/main/shaders/vignette.wgsl
index b129883..c4d0389 100644
--- a/workspaces/main/shaders/vignette.wgsl
+++ b/workspaces/main/shaders/vignette.wgsl
@@ -10,15 +10,7 @@ struct VignetteParams {
 @group(0) @binding(2) var<uniform> common_uniforms: CommonUniforms;
 @group(0) @binding(3) var<uniform> params: VignetteParams;
 
-@vertex
-fn vs_main(@builtin(vertex_index) vertex_idx: u32) -> @builtin(position) vec4<f32> {
-  var pos = array<vec2<f32>, 3>(
-    vec2<f32>(-1.0, -1.0),
-    vec2<f32>(3.0, -1.0),
-    vec2<f32>(-1.0, 3.0)
-  );
-  return vec4<f32>(pos[vertex_idx], 0.0, 1.0);
-}
+#include "render/fullscreen_vs"
 
 @fragment
 fn fs_main(@builtin(position) pos: vec4<f32>) -> @location(0) vec4<f32> {