Mastering Custom Collision Contacts In Unity For Unique Effects

Unity's built-in physics system works well for most games, but sometimes you need more control over how collisions behave. In this video, we explore Unity’s `ContactModifyEvent` which lets you intercept and modify physics contacts at runtime — even while the solver is running across multiple threads. You'll learn how to ignore contacts based on position or direction, implement one-way walls using dot products, simulate conveyor belts by injecting tangential velocity, and track which triangles in a mesh collider were touched during collision. We also cover best practices for thread safety, using data structures like `ConcurrentHashSet` to collect contact info without breaking Unity’s multithreaded physics constraints. If you're building gameplay systems that need custom collision behavior — or you're just curious how deep Unity's physics hooks go — this video is for you. More Reading: https://medium.com/waveaccess/contacts-modification-api-in-unity-d65deba6f7c Want to support me? 😀 Buy me a coffee! https://ko-fi.com/adammyhre 🔔 Subscribe for more Unity Tutorials https://youtube.com/@git-amend Discord: https://discord.gg/FDRZGQBBUC #unity3d #gamedev #indiedev ▬ Contents of this video ▬▬▬▬▬▬▬▬▬▬ More Useful Code: https://github.com/adammyhre?tab=repositories Unity Utility Library: https://github.com/adammyhre/Unity-Utils Lock Inspector Hotkey: https://gist.github.com/adammyhre/4754f731a93bf1cab0d1385ccfa23642 *Assets Shown In This Video* _(Affiliate Links)_ All in 1 3D Shader = https://assetstore.unity.com/packages/vfx/shaders/all-in-1-3d-shader-316173?aid=1101lw3sv Beautify - https://assetstore.unity.com/packages/vfx/shaders/fullscreen-camera-effects/beautify-3-advanced-post-processing-233073?aid=1101lw3sv Umbra Soft Shadows - https://assetstore.unity.com/packages/vfx/shaders/fullscreen-camera-effects/umbra-soft-shadows-better-directional-contact-shadows-for-urp-282485?aid=1101lw3sv Wingman - https://assetstore.unity.com/packages/tools/utilities/wingman-your-inspector-s-best-friend-303181?aid=1101lw3sv Favorites Window - https://assetstore.unity.com/packages/tools/utilities/favorites-window-123487?aid=1101lw3sv Logwin - https://assetstore.unity.com/packages/tools/utilities/logwin-log-debug-values-tracker-149558?aid=1101lw3sv TimeScale Toolbar - https://assetstore.unity.com/packages/tools/utilities/timescale-toolbar-291564?aid=1101lw3sv Odin - https://assetstore.unity.com/packages/tools/utilities/odin-inspector-and-serializer-89041?aid=1101lw3sv?aid=1101lw3sv Odin Validator - https://assetstore.unity.com/packages/tools/utilities/odin-validator-227861?aid=1101lw3sv Hot Reload: https://assetstore.unity.com/packages/tools/utilities/hot-reload-edit-code-without-compiling-254358?aid=1101lw3sv Better Hierarchy: https://assetstore.unity.com/packages/tools/utilities/better-hierarchy-272963?aid=1101lw3sv Better Transform: https://assetstore.unity.com/packages/tools/utilities/better-transform-size-notes-global-local-workspace-child-parent--276554?aid=1101lw3sv Better Mesh Filter: https://assetstore.unity.com/packages/tools/utilities/better-mesh-filter-266489?aid=1101lw3sv Editor Console Pro: https://assetstore.unity.com/packages/tools/utilities/editor-console-pro-11889?aid=1101lw3sv Any Object Finder: https://assetstore.unity.com/packages/tools/utilities/any-object-finder-286455?aid=1101lw3sv Clipper PRO: https://assetstore.unity.com/packages/tools/utilities/clipper-pro-the-ultimate-clipboard-277112?aid=1101lw3sv Kybernetic Tools: https://assetstore.unity.com/publishers/16747?aid=1101lw3sv Sisus Tools: https://assetstore.unity.com/publishers/41398?aid=1101lw3sv Prime Tween - https://assetstore.unity.com/packages/tools/animation/primetween-high-performance-animations-and-sequences-2529607?aid=1101lw3s Rabbit Logger - https://assetstore.unity.com/packages/tools/utilities/rabbit-logger-305396?aid=1101lw3s *Follow me!* https://linktr.ee/gitamend