feat(physics): Implement SDF-based physics engine and BVH

Completed Task #49.
- Implemented CPU-side SDF library (sphere, box, torus, plane).
- Implemented Dynamic BVH construction (rebuilt every frame).
- Implemented PhysicsSystem with semi-implicit Euler integration and collision resolution.
- Added visual debugging for BVH nodes.
- Created test_3d_physics interactive test and test_physics unit tests.
- Updated project docs and triaged new tasks.

1 files changed, 10 insertions, 0 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 274386a..06b142e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -110,6 +110,8 @@ set(GPU_SOURCES
 set(3D_SOURCES
     src/3d/renderer.cc
     src/3d/visual_debug.cc
+    src/3d/bvh.cc
+    src/3d/physics.cc
 )
 set(PLATFORM_SOURCES src/platform.cc third_party/glfw3webgpu/glfw3webgpu.c)
 set(UTIL_SOURCES src/util/asset_manager.cc)
@@ -139,6 +141,7 @@ if (DEFINED ASSET_PACKER_PATH)
 else()
     add_executable(asset_packer tools/asset_packer.cc)
     target_link_libraries(asset_packer PRIVATE procedural)
+    target_include_directories(asset_packer PRIVATE third_party)
     set(ASSET_PACKER_CMD $<TARGET_FILE:asset_packer>)
     set(ASSET_PACKER_DEPENDS asset_packer)
 endif()
@@ -342,6 +345,9 @@ if(DEMO_BUILD_TESTS)
     add_demo_test(test_procedural ProceduralGenTest src/tests/test_procedural.cc)
     target_link_libraries(test_procedural PRIVATE procedural ${DEMO_LIBS})
 
+    add_demo_test(test_physics PhysicsTest src/tests/test_physics.cc)
+    target_link_libraries(test_physics PRIVATE 3d util procedural ${DEMO_LIBS})
+
     add_demo_test(test_3d ThreeDSystemTest src/tests/test_3d.cc)
 
     add_demo_test(test_shader_composer ShaderComposerTest src/tests/test_shader_composer.cc ${GEN_TEST_CC})
@@ -358,6 +364,10 @@ if(DEMO_BUILD_TESTS)
     add_demo_executable(test_3d_render src/tests/test_3d_render.cc ${PLATFORM_SOURCES} ${GENERATED_TIMELINE_CC} ${GEN_DEMO_CC} ${GENERATED_MUSIC_DATA_CC})
     target_link_libraries(test_3d_render PRIVATE 3d gpu audio procedural util ${DEMO_LIBS})
     add_dependencies(test_3d_render generate_timeline generate_demo_assets generate_tracker_music)
+
+    add_demo_executable(test_3d_physics src/tests/test_3d_physics.cc ${PLATFORM_SOURCES} ${GENERATED_TIMELINE_CC} ${GEN_DEMO_CC} ${GENERATED_MUSIC_DATA_CC})
+    target_link_libraries(test_3d_physics PRIVATE 3d gpu audio procedural util ${DEMO_LIBS})
+    add_dependencies(test_3d_physics generate_timeline generate_demo_assets generate_tracker_music)
 endif()
 
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