refactor[physics] :: remove duplication and add constants

[bniladridas]

Summary

This PR follows up on #9 and addresses cleanup and correctness issues identified during review. It includes minor fixes to physics logic, constants, and module structure.

Why this change?

The initial refactor improved structure and numerical stability, but review feedback highlighted areas needing adjustment. This PR fixes collision logic, aligns imports and constants, clarifies unsupported paths, and updates module documentation and declarations.

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What changed

• Updated physics_engine.rs to import from numerics, fix wall collision logic, and use shared constants
• Added physics constants in constants.rs (PERFECTLY_ELASTIC_RESTITUTION, WALL_BOUNCE_DAMPING_FACTOR, MAX_COORDINATE_VALUE)
• Marked unsupported constraints explicitly using unimplemented! in physics_constraints.rs
• Fixed module documentation in utilities.rs
• Added PR title format guidelines to CONTRIBUTING.md
• Adjusted module declarations in main.rs

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Impact

• Refactor / cleanup
• Bug fix (wall collision logic)

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Testing

• Unit tests (all physics tests pass)
• Manual testing (verified collision and gravity behavior)

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Notes for reviewers

• Changes preserve backward compatibility
• All tests and pre-commit checks pass

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Closes #11

[gemini-code-assist]

Summary of Changes

Hello @bniladridas, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refactors core components of the physics engine to enhance its robustness, correctness, and maintainability. It centralizes numerical utility functions to reduce duplication, fixes a logical error in wall collision detection, and improves code clarity by introducing named constants for key physical properties and limits. These changes collectively aim to make the simulation more accurate and the codebase easier to understand and extend, alongside updating project contribution standards.

Highlights

• Code Duplication: Eliminated redundant numeric utility functions in physics_engine.rs by importing them from the numerics module, establishing a single source of truth.
• Wall Collision Logic: Corrected wall collision behavior to only apply bounce effects when objects are moving towards the boundary, preventing incorrect bounces when moving away.
• Constants Introduction: Introduced named constants for restitution, wall bounce damping, and coordinate limits, significantly improving code readability and maintainability.
• Impulse Calculation: Enhanced collision impulse calculation by utilizing inverse masses, aligning with physics engine best practices for more accurate simulations.
• Documentation & Guidelines: Updated module documentation in utilities.rs and added clear Pull Request title format guidelines to CONTRIBUTING.md.

Ignored Files

• Ignored by pattern: .github/workflows/** (1)
  • .github/workflows/pull_request_template.md

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[gemini-code-assist]

Code Review

This pull request primarily refactors the physics engine by extracting numerical utilities and constants into a dedicated numerics module, improving modularity and centralizing values. Specifically, functions like clamp, safe_divide, clamp_velocity, validate_vector, and approx_eq were moved, and new constants such as EARTH_GRAVITY, PERFECTLY_ELASTIC_RESTITUTION, WALL_BOUNCE_DAMPING_FACTOR, and MAX_COORDINATE_VALUE were introduced. The Object::new constructor and PhysicsEngine calculations were updated to utilize these new utilities and constants, including a refinement of the wall bouncing logic to apply damping only when objects are moving towards a boundary. Additionally, the CONTRIBUTING.md file was updated with guidelines for pull request title formatting, engine/main.rs was modified to import simulation_manager from an external simulation_engine crate, and physics_constraints.rs now explicitly marks Distance and Axis constraints as unimplemented.

[bniladridas]

Follow up to the pr was created on 2026-01-04T20:05:15Z