Offset Geometric Contact — Interactive Physics Demonstration

This is an interactive educational demonstration of the Offset Geometric Contact paper—a novel contact simulation algorithm that guarantees penetration-free physics. The demo lets you spawn objects, watch them stack stably, and visualize contact forces as cyan arrows pointing perpendicular to surfaces. The key innovation: orthogonal forces eliminate stretching artifacts and enable large contact radii without instability, running 100× faster than competing methods like Incremental Potential Contact (IPC).

The project is split into two modes. Mode 1 covers basic interaction: drop objects onto a pre-built stack, change object types, toggle wind for cloth simulation, and observe contact visualization in real-time. Mode 2 adds six physically difficult scenarios—Newton's Cradle (momentum transfer), Jenga tower (stability under asymmetric loading), hanging chain (self-collision), domino effect (sequential contact), gear system (angular momentum), and thin-shell collapse (edge-edge contact)—each designed to stress-test aspects that typical engines handle poorly.

Implementation centers on position-based dynamics and custom constraint solving rather than Unity's built-in joints. A new OGCConstraint component replaces ConfigurableJoint for ropes and strings, using local distance constraints instead of global force-based solving. The ContactVisualizer renders contact points (green spheres) and orthogonal normals (cyan arrows) every frame, making the paper's core innovation immediately visible. All UI responds to keyboard input; the menu system includes one-click scene setup for both demo modes.