docs: Update project documentation and regenerate assets

Updated PROJECT_CONTEXT.md and TODO.md to include new critical tasks and reflect changes in task prioritization.
Modified doc/3D.md to adjust task descriptions.
Modified doc/CONTRIBUTING.md to incorporate the new in-memory replacement rule.
Regenerated asset files (src/generated/assets.h, src/generated/assets_data.cc, src/generated/test_assets.h, src/generated/test_assets_data.cc) to reflect any changes in asset definitions.
Removed temporary changes to GEMINI.md and HANDOFF.md.

1 files changed, 19 insertions, 8 deletions

diff --git a/doc/3D.md b/doc/3D.md
index 5bda566..59af47c 100644
--- a/doc/3D.md
+++ b/doc/3D.md
@@ -153,15 +153,26 @@ Instead of full SDF-on-SDF intersection (which is expensive), we approximate dyn
     *   **Normal**: Compute gradient $N = \nabla SDF_B(P_{local})$ via central differences. Transform $N$ back to world space.
     *   **Contact Point**: $P_{contact} = P_{world} - N * p$.
 
-### Solver Loop (Semi-Implicit Euler)
-1.  **Integrate Velocity**: `vel += gravity * dt`.
+### Narrow Phase & Resolution:
+*   If collision detected (depth $p > 0$):
+    *   **Positional Correction**: Move object by $N * p$ (to resolve penetration).
+    *   **Velocity Response (PBD)**: In Position Based Dynamics (PBD), the velocity is re-evaluated *after* all collisions and constraints have been resolved: `v = (p_new - p_old) / dt`.
+    *   **Friction**: Apply tangential damping.
+
+### Rotation & Angular Momentum
+Objects should support rotation via **Quaternions**.
+*   **State**: Add `quat orientation` and `vec3 angular_velocity` to `Object3D`.
+*   **Integration**: Update orientation using angular velocity: `q = q + 0.5 * dt * [0, w] * q`, then normalize.
+*   **Narrow Phase**: Proxy points must be rotated by the quaternion: `P_local = Inverse(Q) * (P_world - Position)`.
+*   **Collision Response**: Collision impulses should affect both linear and angular momentum.
+
+### Solver Loop (Position Based Dynamics)
+1.  **Integrate Position (Predicted)**: `p_pred = p + v * dt`.
 2.  **Broad Phase**: Find pairs using BVH.
 3.  **Narrow Phase & Resolution**:
-    *   If collision detected (depth $p > 0$):
-        *   **Positional Correction**: Move object by $N * p$ (to resolve penetration).
-        *   **Velocity Response**: `vel = vel - (1 + restitution) * dot(vel, N) * N`.
-        *   **Friction**: Apply tangential damping.
-4.  **Integrate Position**: `pos += vel * dt`.
+    *   Resolve penetrations and constraints on `p_pred`.
+4.  **Update Velocity**: `v = (p_pred - p) / dt`.
+5.  **Finalize Position**: `p = p_pred`.
 
 ### Code Integration Plan
 
@@ -183,4 +194,4 @@ our AssetManager or as c++ code directly) - **Task #36: Blender Exporter**.
 ## latter improvement
 
 How to handle transparency? Multi-Ray-casting?
-We need to think about the lighting strategy. - **Task #40: Advanced Lighting & Transparency**.
+We need to think about the lighting strategy. - **Task #40: Advanced Lighting & Transparency**.
\ No newline at end of file