feat(scene1): replace ad-hoc camera with CameraParams uniform

Build camera via mat4::look_at + inverse in scene1_effect.cc, upload as
CameraParams at binding 3. Shader uses getCameraRay() from camera_common.
Enable camera_common snippet registration in shaders.cc.

handoff(Claude): Scene1 camera now driven by CameraParams uniform; fov=TAU/6 (60° vFOV) matches original tan(PI/3) parameterization.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 19 insertions, 1 deletions

diff --git a/src/effects/scene1_effect.cc b/src/effects/scene1_effect.cc
index 7c109e7..da2797c 100644
--- a/src/effects/scene1_effect.cc
+++ b/src/effects/scene1_effect.cc
@@ -5,6 +5,21 @@
 #include "gpu/gpu.h"
 #include "gpu/post_process_helper.h"
 #include "util/fatal_error.h"
+#include "util/mini_math.h"
+
+static CameraParams make_scene1_camera() {
+  const float TAU = 6.283185307f;
+  const vec3 ro(0.0f, 2.5f, 5.0f);
+  const vec3 la(0.0f, 0.0f, 0.0f);
+  const vec3 up(0.1f, 1.0f, 0.0f);
+  CameraParams cam;
+  cam.inv_view = mat4::look_at(ro, la, up).inverse();
+  cam.fov = TAU / 6.0f;  // full vfov=60°; tan(fov/2)=tan(PI/6)=1/sqrt(3)=1/shader_fov
+  cam.near_plane = 0.1f;
+  cam.far_plane = 100.0f;
+  cam.aspect_ratio = 1.0f;  // aspect handled in fs_main
+  return cam;
+}
 
 Scene1::Scene1(const GpuContext& ctx, const std::vector<std::string>& inputs,
                const std::vector<std::string>& outputs, float start_time,
@@ -15,6 +30,9 @@ Scene1::Scene1(const GpuContext& ctx, const std::vector<std::string>& inputs,
   create_nearest_sampler();
   create_dummy_scene_texture();
 
+  camera_params_.init(ctx_.device);
+  camera_params_.update(ctx_.queue, make_scene1_camera());
+
   pipeline_.set(create_post_process_pipeline(
       ctx_.device, WGPUTextureFormat_RGBA8Unorm, scene1_shader_wgsl));
 }
@@ -26,7 +44,7 @@ void Scene1::render(WGPUCommandEncoder encoder,
 
   pp_update_bind_group(ctx_.device, pipeline_.get(), bind_group_.get_address(),
                        dummy_texture_view_.get(), uniforms_buffer_.get(),
-                       {nullptr, 0});
+                       camera_params_.get());
 
   WGPURenderPassColorAttachment color_attachment = {};
   gpu_init_color_attachment(color_attachment, output_view);