refactor(wgsl): consolidate SDF shapes into single common file

Merge sdf_primitives.wgsl into math/sdf_shapes.wgsl to eliminate
duplication and establish single source of truth for all SDF functions.

Changes:
- Delete common/shaders/sdf_primitives.wgsl (duplicate of math/sdf_shapes.wgsl)
- Add sdBox2D() and sdEllipse() to math/sdf_shapes.wgsl
- Update ellipse.wgsl (main/test) to use #include "math/sdf_shapes"
- Update scene1.wgsl to use math/sdf_shapes instead of sdf_primitives
- Rename asset SHADER_SDF_PRIMITIVES → SHADER_SDF_SHAPES
- Update shader registration and tests

Impact:
- ~60 lines eliminated from ellipse shaders
- Single source for 3D primitives (sphere, box, torus, plane) and 2D (box, ellipse)
- Consistent include path across codebase

All tests passing (34/34).

handoff(Claude): SDF shapes consolidated to math/sdf_shapes.wgsl

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

10 files changed, 66 insertions, 90 deletions

diff --git a/common/shaders/math/sdf_shapes.wgsl b/common/shaders/math/sdf_shapes.wgsl
index 31bbe2d..64df4fc 100644
--- a/common/shaders/math/sdf_shapes.wgsl
+++ b/common/shaders/math/sdf_shapes.wgsl
@@ -1,14 +1,56 @@
+// 3D SDF primitives
 fn sdSphere(p: vec3<f32>, r: f32) -> f32 {
     return length(p) - r;
 }
+
 fn sdBox(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 sdTorus(p: vec3<f32>, t: vec2<f32>) -> f32 {
     let q = vec2<f32>(length(p.xz) - t.x, p.y);
     return length(q) - t.y;
 }
+
 fn sdPlane(p: vec3<f32>, n: vec3<f32>, h: f32) -> f32 {
-  return dot(p, n) + h;
+    return dot(p, n) + h;
+}
+
+// 2D SDF primitives
+fn sdBox2D(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 sdEllipse(p: vec2<f32>, ab: vec2<f32>) -> f32 {
+    var p_abs = abs(p);
+    if (p_abs.x > p_abs.y) {
+        p_abs = vec2<f32>(p_abs.y, p_abs.x);
+    }
+    let l = ab.y * ab.y - ab.x * ab.x;
+    let m = ab.x * p_abs.x / l;
+    let n = ab.y * p_abs.y / l;
+    let m2 = m * m;
+    let n2 = n * n;
+    let c = (m2 + n2 - 1.0) / 3.0;
+    let c3 = c * c * c;
+    let d = c3 + m2 * n2;
+    let g = m + m * n2;
+    var co: f32;
+    if (d < 0.0) {
+        let h = acos((c3 + m2 * n2 * 2.0) / c3) / 3.0;
+        let s = cos(h);
+        let t = sin(h) * sqrt(3.0);
+        co = (sqrt(-c * (s + t * 2.0) + m2) + sign(l) * sqrt(-c * (s - t * 2.0) + m2) + abs(g) / (sqrt(-c * (s + t * 2.0) + m2) * sqrt(-c * (s - t * 2.0) + m2)) - m) / 2.0;
+    } else {
+        let h = 2.0 * m * n * sqrt(d);
+        let s = sign(c3 + m2 * n2 + h) * pow(abs(c3 + m2 * n2 + h), 1.0 / 3.0);
+        let u = sign(c3 + m2 * n2 - h) * pow(abs(c3 + m2 * n2 - h), 1.0 / 3.0);
+        let rx = -s - u + m2 * 2.0;
+        let ry = (s - u) * sqrt(3.0);
+        co = (ry / sqrt(sqrt(rx * rx + ry * ry) - rx) + 2.0 * g / sqrt(rx * rx + ry * ry) - m) / 2.0;
+    }
+    let si = sqrt(max(0.0, 1.0 - co * co));
+    return length(p_abs - vec2<f32>(ab.x * co, ab.y * si)) * sign(p_abs.y * ab.x * co - p_abs.x * ab.y * si);
 }
diff --git a/common/shaders/sdf_primitives.wgsl b/common/shaders/sdf_primitives.wgsl
deleted file mode 100644
index 407fb29..0000000
--- a/common/shaders/sdf_primitives.wgsl
+++ /dev/null
@@ -1,19 +0,0 @@
-fn sdSphere(p: vec3<f32>, r: f32) -> f32 {
-    return length(p) - r;
-}
-fn sdBox(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 sdTorus(p: vec3<f32>, t: vec2<f32>) -> f32 {
-    let q = vec2<f32>(length(p.xz) - t.x, p.y);
-    return length(q) - t.y;
-}
-fn sdPlane(p: vec3<f32>, n: vec3<f32>, h: f32) -> f32 {
-  return dot(p, n) + h;
-}
-
-fn sdBox2D(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);
-}
diff --git a/doc/COMPLETED.md b/doc/COMPLETED.md
index dddcc3e..1acf8d1 100644
--- a/doc/COMPLETED.md
+++ b/doc/COMPLETED.md
@@ -31,6 +31,21 @@ Use `read @doc/archive/FILENAME.md` to access archived documents.
 
 ## Recently Completed (February 14, 2026)
 
+- [x] **SDF Shapes Consolidation**
+    - **Goal**: Consolidate duplicate SDF primitive definitions into single source
+    - **Changes**:
+      - Merged `sdf_primitives.wgsl` into `math/sdf_shapes.wgsl`
+      - Added `sdBox2D()` and `sdEllipse()` to common shapes
+      - Removed duplicate sdEllipse from ellipse.wgsl shaders (main/test)
+      - Updated scene1.wgsl to use `math/sdf_shapes` include
+      - Renamed asset from SHADER_SDF_PRIMITIVES to SHADER_SDF_SHAPES
+    - **Impact**:
+      - ~60 lines eliminated from ellipse shaders
+      - Single source of truth for all SDF primitives (3D: sphere, box, torus, plane; 2D: box, ellipse)
+      - Consistent include path: `#include "math/sdf_shapes"`
+    - **Result**: 34/34 tests passing (100%)
+    - **Related**: Task #50 (WGSL Modularization)
+
 - [x] **Fullscreen Vertex Shader Modularization**
     - **Goal**: Eliminate duplicate fullscreen triangle vertex shader code
     - **Changes**:
diff --git a/src/gpu/shaders.cc b/src/gpu/shaders.cc
index 60db655..1bf5604 100644
--- a/src/gpu/shaders.cc
+++ b/src/gpu/shaders.cc
@@ -45,7 +45,7 @@ void InitShaderComposer() {
                      AssetId::ASSET_SHADER_RENDER_LIGHTING_UTILS);
   register_if_exists("render/mesh", AssetId::ASSET_SHADER_MESH);
 
-  register_if_exists("sdf_primitives", AssetId::ASSET_SHADER_SDF_PRIMITIVES);
+  register_if_exists("math/sdf_shapes", AssetId::ASSET_SHADER_SDF_SHAPES);
 
   register_if_exists("lighting", AssetId::ASSET_SHADER_LIGHTING);
 
diff --git a/src/tests/gpu/test_shader_assets.cc b/src/tests/gpu/test_shader_assets.cc
index 1736dc0..135c477 100644
--- a/src/tests/gpu/test_shader_assets.cc
+++ b/src/tests/gpu/test_shader_assets.cc
@@ -42,8 +42,8 @@ int main() {
   all_passed &=
       validate_shader(AssetId::ASSET_SHADER_COMMON_UNIFORMS, "COMMON_UNIFORMS",
                       {"struct", "GlobalUniforms"});
-  all_passed &= validate_shader(AssetId::ASSET_SHADER_SDF_PRIMITIVES,
-                                "SDF_PRIMITIVES", {"fn", "sd"});
+  all_passed &= validate_shader(AssetId::ASSET_SHADER_SDF_SHAPES,
+                                "SDF_SHAPES", {"fn", "sd"});
   all_passed &= validate_shader(AssetId::ASSET_SHADER_LIGHTING, "LIGHTING",
                                 {"fn", "calc"});
   all_passed &= validate_shader(AssetId::ASSET_SHADER_RAY_BOX, "RAY_BOX",
diff --git a/workspaces/main/assets.txt b/workspaces/main/assets.txt
index ace1462..0b64ba9 100644
--- a/workspaces/main/assets.txt
+++ b/workspaces/main/assets.txt
@@ -25,7 +25,7 @@ NOISE_TEX, PROC(gen_noise, 1234, 16), _, "Procedural noise texture for bump mapp
 # --- WGSL Shaders & Snippets ---
 SHADER_RENDERER_3D, NONE, shaders/renderer_3d.wgsl, "Hybrid 3D Renderer Shader"
 SHADER_COMMON_UNIFORMS, NONE, ../../common/shaders/common_uniforms.wgsl, "Common Uniforms Snippet"
-SHADER_SDF_PRIMITIVES, NONE, ../../common/shaders/sdf_primitives.wgsl, "SDF Primitives Snippet"
+SHADER_SDF_SHAPES, NONE, ../../common/shaders/math/sdf_shapes.wgsl, "SDF Shapes (2D/3D primitives)"
 SHADER_LIGHTING, NONE, ../../common/shaders/lighting.wgsl, "Lighting Snippet"
 SHADER_RAY_BOX, NONE, ../../common/shaders/ray_box.wgsl, "Ray-Box Intersection Snippet"
 SHADER_RAY_TRIANGLE, NONE, ../../common/shaders/ray_triangle.wgsl, "Ray-Triangle Intersection Snippet (Möller-Trumbore)"
diff --git a/workspaces/main/shaders/ellipse.wgsl b/workspaces/main/shaders/ellipse.wgsl
index 07f0c9a..0aaa4ae 100644
--- a/workspaces/main/shaders/ellipse.wgsl
+++ b/workspaces/main/shaders/ellipse.wgsl
@@ -1,40 +1,9 @@
 #include "common_uniforms"
 #include "render/fullscreen_vs"
+#include "math/sdf_shapes"
 
 @group(0) @binding(0) var<uniform> uniforms: CommonUniforms;
 
-fn sdEllipse(p: vec2<f32>, ab: vec2<f32>) -> f32 {
-    var p_abs = abs(p);
-    if (p_abs.x > p_abs.y) {
-        p_abs = vec2<f32>(p_abs.y, p_abs.x);
-    }
-    let l = ab.y * ab.y - ab.x * ab.x;
-    let m = ab.x * p_abs.x / l;
-    let n = ab.y * p_abs.y / l;
-    let m2 = m * m;
-    let n2 = n * n;
-    let c = (m2 + n2 - 1.0) / 3.0;
-    let c3 = c * c * c;
-    let d = c3 + m2 * n2;
-    let g = m + m * n2;
-    var co: f32;
-    if (d < 0.0) {
-        let h = acos((c3 + m2 * n2 * 2.0) / c3) / 3.0;
-        let s = cos(h);
-        let t = sin(h) * sqrt(3.0);
-        co = (sqrt(-c * (s + t * 2.0) + m2) + sign(l) * sqrt(-c * (s - t * 2.0) + m2) + abs(g) / (sqrt(-c * (s + t * 2.0) + m2) * sqrt(-c * (s - t * 2.0) + m2)) - m) / 2.0;
-    } else {
-        let h = 2.0 * m * n * sqrt(d);
-        let s = sign(c3 + m2 * n2 + h) * pow(abs(c3 + m2 * n2 + h), 1.0 / 3.0);
-        let u = sign(c3 + m2 * n2 - h) * pow(abs(c3 + m2 * n2 - h), 1.0 / 3.0);
-        let rx = -s - u + m2 * 2.0;
-        let ry = (s - u) * sqrt(3.0);
-        co = (ry / sqrt(sqrt(rx * rx + ry * ry) - rx) + 2.0 * g / sqrt(rx * rx + ry * ry) - m) / 2.0;
-    }
-    let si = sqrt(max(0.0, 1.0 - co * co));
-    return length(p_abs - vec2<f32>(ab.x * co, ab.y * si)) * sign(p_abs.y * ab.x * co - p_abs.x * ab.y * si);
-}
-
 @fragment fn fs_main(@builtin(position) p: vec4<f32>) -> @location(0) vec4<f32> {
     let uv = (p.xy / uniforms.resolution - 0.5) * 2.0;
     let movement = vec2<f32>(sin(uniforms.time * 0.7), cos(uniforms.time * 0.5));
diff --git a/workspaces/main/shaders/scene1.wgsl b/workspaces/main/shaders/scene1.wgsl
index 2a811f7..2723b66 100644
--- a/workspaces/main/shaders/scene1.wgsl
+++ b/workspaces/main/shaders/scene1.wgsl
@@ -4,7 +4,7 @@
 #include "common_uniforms"
 #include "math/color"
 #include "math/utils"
-#include "sdf_primitives"
+#include "math/sdf_shapes"
 #include "render/raymarching"
 
 @group(0) @binding(0) var<uniform> uniforms: CommonUniforms;
diff --git a/workspaces/test/assets.txt b/workspaces/test/assets.txt
index b717e15..8eb692e 100644
--- a/workspaces/test/assets.txt
+++ b/workspaces/test/assets.txt
@@ -25,7 +25,7 @@ NOISE_TEX, PROC(gen_noise, 1234, 16), _, "Procedural noise texture for bump mapp
 # --- WGSL Shaders & Snippets ---
 SHADER_RENDERER_3D, NONE, shaders/renderer_3d.wgsl, "Hybrid 3D Renderer Shader"
 SHADER_COMMON_UNIFORMS, NONE, ../../common/shaders/common_uniforms.wgsl, "Common Uniforms Snippet"
-SHADER_SDF_PRIMITIVES, NONE, ../../common/shaders/sdf_primitives.wgsl, "SDF Primitives Snippet"
+SHADER_SDF_SHAPES, NONE, ../../common/shaders/math/sdf_shapes.wgsl, "SDF Shapes (2D/3D primitives)"
 SHADER_LIGHTING, NONE, ../../common/shaders/lighting.wgsl, "Lighting Snippet"
 SHADER_RAY_BOX, NONE, ../../common/shaders/ray_box.wgsl, "Ray-Box Intersection Snippet"
 SHADER_RAY_TRIANGLE, NONE, ../../common/shaders/ray_triangle.wgsl, "Ray-Triangle Intersection Snippet (Möller-Trumbore)"
diff --git a/workspaces/test/shaders/ellipse.wgsl b/workspaces/test/shaders/ellipse.wgsl
index 07f0c9a..0aaa4ae 100644
--- a/workspaces/test/shaders/ellipse.wgsl
+++ b/workspaces/test/shaders/ellipse.wgsl
@@ -1,40 +1,9 @@
 #include "common_uniforms"
 #include "render/fullscreen_vs"
+#include "math/sdf_shapes"
 
 @group(0) @binding(0) var<uniform> uniforms: CommonUniforms;
 
-fn sdEllipse(p: vec2<f32>, ab: vec2<f32>) -> f32 {
-    var p_abs = abs(p);
-    if (p_abs.x > p_abs.y) {
-        p_abs = vec2<f32>(p_abs.y, p_abs.x);
-    }
-    let l = ab.y * ab.y - ab.x * ab.x;
-    let m = ab.x * p_abs.x / l;
-    let n = ab.y * p_abs.y / l;
-    let m2 = m * m;
-    let n2 = n * n;
-    let c = (m2 + n2 - 1.0) / 3.0;
-    let c3 = c * c * c;
-    let d = c3 + m2 * n2;
-    let g = m + m * n2;
-    var co: f32;
-    if (d < 0.0) {
-        let h = acos((c3 + m2 * n2 * 2.0) / c3) / 3.0;
-        let s = cos(h);
-        let t = sin(h) * sqrt(3.0);
-        co = (sqrt(-c * (s + t * 2.0) + m2) + sign(l) * sqrt(-c * (s - t * 2.0) + m2) + abs(g) / (sqrt(-c * (s + t * 2.0) + m2) * sqrt(-c * (s - t * 2.0) + m2)) - m) / 2.0;
-    } else {
-        let h = 2.0 * m * n * sqrt(d);
-        let s = sign(c3 + m2 * n2 + h) * pow(abs(c3 + m2 * n2 + h), 1.0 / 3.0);
-        let u = sign(c3 + m2 * n2 - h) * pow(abs(c3 + m2 * n2 - h), 1.0 / 3.0);
-        let rx = -s - u + m2 * 2.0;
-        let ry = (s - u) * sqrt(3.0);
-        co = (ry / sqrt(sqrt(rx * rx + ry * ry) - rx) + 2.0 * g / sqrt(rx * rx + ry * ry) - m) / 2.0;
-    }
-    let si = sqrt(max(0.0, 1.0 - co * co));
-    return length(p_abs - vec2<f32>(ab.x * co, ab.y * si)) * sign(p_abs.y * ab.x * co - p_abs.x * ab.y * si);
-}
-
 @fragment fn fs_main(@builtin(position) p: vec4<f32>) -> @location(0) vec4<f32> {
     let uv = (p.xy / uniforms.resolution - 0.5) * 2.0;
     let movement = vec2<f32>(sin(uniforms.time * 0.7), cos(uniforms.time * 0.5));