fix(cnn_v3): call set_scene() in constructor + orbiting camera

- GBufferEffect::render() was a no-op (scene_ready_=false) because
  set_scene() was never called from the timeline sequence constructor.
  Fixed by calling set_scene() at the end of the constructor.
- Camera now orbits the scene at 0.3 rad/s (R=6, y=2.5).

handoff(Gemini): cnn_v3_test sequence now renders G-buffer + GBufViewEffect with animated orbiting camera.

1 files changed, 9 insertions, 0 deletions

diff --git a/cnn_v3/src/gbuffer_effect.cc b/cnn_v3/src/gbuffer_effect.cc
index 06e5e66..ff78cf8 100644
--- a/cnn_v3/src/gbuffer_effect.cc
+++ b/cnn_v3/src/gbuffer_effect.cc
@@ -74,6 +74,8 @@ GBufferEffect::GBufferEffect(const GpuContext& ctx,
   create_raster_pipeline();
   create_shadow_pipeline();
   create_pack_pipeline();
+
+  set_scene();
 }
 
 void GBufferEffect::declare_nodes(NodeRegistry& registry) {
@@ -189,6 +191,13 @@ void GBufferEffect::render(WGPUCommandEncoder encoder,
   // Update camera aspect ratio from current resolution.
   camera_.aspect_ratio = params.aspect_ratio;
 
+  // Slowly orbit around the scene.
+  const float angle = params.time * 0.3f;
+  const float R = 6.0f;
+  camera_.set_look_at(vec3(R * sinf(angle), 2.5f, R * cosf(angle)),
+                      vec3(0.0f, 0.0f, 0.0f),
+                      vec3(0.0f, 1.0f, 0.0f));
+
   // Animate cubes: axis-angle rotation driven by physical time.
   for (int i = 0; i < (int)cube_anims_.size(); ++i) {
     const CubeAnim& a = cube_anims_[(size_t)i];