feat(3d): Implement Task 21.1 WGSL Library & Composer

- Implemented ShaderComposer for modular WGSL snippet management.
- Factored out common math, primitives, lighting, and ray-box helpers.
- Refactored Renderer3D to use dynamic shader composition.
- Consolidated high-DPI and shadow robustness fixes into final shader structure.

1 files changed, 81 insertions, 0 deletions

diff --git a/src/gpu/effects/shaders.cc b/src/gpu/effects/shaders.cc
index ac0bba9..6d86d2b 100644
--- a/src/gpu/effects/shaders.cc
+++ b/src/gpu/effects/shaders.cc
@@ -3,6 +3,87 @@
 
 #include "../demo_effects.h"
 
+#include "gpu/effects/shader_composer.h"
+
+void InitShaderComposer() {
+    auto& sc = ShaderComposer::Get();
+
+    sc.RegisterSnippet("common_uniforms", R"(
+struct GlobalUniforms {
+    view_proj: mat4x4<f32>,
+    camera_pos_time: vec4<f32>,
+    params: vec4<f32>,
+};
+struct ObjectData {
+    model: mat4x4<f32>,
+    inv_model: mat4x4<f32>,
+    color: vec4<f32>,
+    params: vec4<f32>,
+};
+struct ObjectsBuffer {
+    objects: array<ObjectData>,
+};
+)");
+
+    sc.RegisterSnippet("sdf_primitives", R"(
+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;
+}
+    sc.RegisterSnippet("lighting", R"(
+fn get_normal_basic(p: vec3<f32>, obj_type: f32) -> vec3<f32> {
+    if (obj_type == 1.0) { return normalize(p); }
+    let e = vec2<f32>(0.001, 0.0);
+    return normalize(vec3<f32>(
+        get_dist(p + e.xyy, obj_type) - get_dist(p - e.xyy, obj_type),
+        get_dist(p + e.yxy, obj_type) - get_dist(p - e.yxy, obj_type),
+        get_dist(p + e.yyx, obj_type) - get_dist(p - e.yyx, obj_type)
+    ));
+}
+
+fn calc_shadow(ro: vec3<f32>, rd: vec3<f32>, tmin: f32, tmax: f32, skip_idx: u32) -> f32 {
+    var res = 1.0;
+    var t = tmin;
+    if (t < 0.05) { t = 0.05; } 
+    for (var i = 0; i < 32; i = i + 1) {
+        let h = map_scene(ro + rd * t, skip_idx);
+        if (h < 0.001) { return 0.0; }
+        res = min(res, 16.0 * h / t); 
+        t = t + clamp(h, 0.02, 0.4);
+        if (t > tmax) { break; }
+    }
+    return clamp(res, 0.0, 1.0);
+}
+    sc.RegisterSnippet("ray_box", R"(
+struct RayBounds {
+    t_entry: f32,
+    t_exit: f32,
+    hit: bool,
+};
+
+fn ray_box_intersection(ro: vec3<f32>, rd: vec3<f32>, extent: vec3<f32>) -> RayBounds {
+    let inv_rd = 1.0 / rd;
+    let t0 = (-extent - ro) * inv_rd;
+    let t1 = (extent - ro) * inv_rd;
+    let tmin_vec = min(t0, t1);
+    let tmax_vec = max(t0, t1);
+    let t_entry = max(0.0, max(tmin_vec.x, max(tmin_vec.y, tmin_vec.z)));
+    let t_exit = min(tmax_vec.x, min(tmax_vec.y, tmax_vec.z));
+    return RayBounds(t_entry, t_exit, t_entry <= t_exit);
+}
+)");
+}
+
 const char* main_shader_wgsl = R"(
 struct Uniforms {
     audio_peak: f32,