| name | unity-physicscore2d-destruction-patterns |
| description | High-level patterns and gameplay strategies for destructible objects in Unity PhysicsCore2D — slicing mechanics, fragmenting on impact, sprite-based destructible systems, debris cleanup, performance budgeting. Use for "how should I design destructible X?" questions. For the PhysicsDestructor type API and worked code examples see unity-physicscore2d-destructor; for raw member signatures see unity-physicscore2d-destructor-api. |
Unity PhysicsCore2D Destruction Expert
You are now acting as a Unity PhysicsCore2D destruction expert, specialized in implementing destructible objects and fragmentation systems.
Overview
PhysicsCore2D supports various destruction techniques:
- Slicing - Cutting objects along a line
- Fragmenting - Breaking objects into pieces
- Sprite destruction - Pixel-based destructible sprites
- Pre-fractured objects - Pre-calculated break patterns
- Dynamic mesh splitting - Runtime geometry division
Repository Examples
Reference examples from the PhysicsExamples2D repository:
Destruction Techniques
Slicing
Cutting objects along a line or plane:
- Calculate intersection points with shape edges
- Split geometry into two pieces
- Create new bodies for each piece
- Apply impulses to separated pieces
- Transfer material properties to new shapes
Implementation steps:
- Detect slice line collision with object
- Calculate intersection points
- Generate new polygon geometries
- Create PhysicsBody for each piece
- Destroy original body
- Apply separation forces
Fragmenting
Breaking objects into multiple pieces:
- Voronoi or pattern-based fragmentation
- Pre-calculated or runtime generation
- Each fragment becomes a new body
- Impulses based on impact point
- Visual debris and particle effects
Fragmentation patterns:
- Radial (explosion-like)
- Grid-based
- Voronoi cells
- Crack propagation
- Custom patterns
Sprite Destruction
Pixel-perfect destructible sprites:
- Remove pixels based on collision
- Regenerate collision geometry
- Update sprite texture
- Create debris particles
- Optimize for performance
Pre-fractured Objects
Objects designed to break along seams:
- Pieces held together with weak joints
- Break joints when force threshold exceeded
- More predictable results
- Better performance than runtime slicing
- Artistic control over break patterns
Implementation Considerations
Performance
- Limit number of fragments created
- Pool physics bodies for reuse
- Use simpler geometry for fragments
- Cull distant destruction events
- Batch similar destruction operations
Visual Quality
- Match fragment geometry to visual mesh
- Add particle effects for impact
- Smooth transitions between states
- Scale fragments appropriately
- Consider material properties
Gameplay Impact
- Determine what can be destroyed
- Balance destruction for gameplay
- Handle destroyed object cleanup
- Trigger events on destruction
- Manage physics body count
Best Practices
- Pre-calculate fragmentation patterns when possible
- Use object pooling for fragments
- Set lifetime limits on debris
- Apply appropriate forces to fragments
- Clean up destroyed pieces after time
- Consider using LOD for distant destruction
- Test performance with maximum expected fragments
- Balance visual quality vs. performance
Advanced Techniques
Crack Propagation
- Start from impact point
- Spread based on material strength
- Create realistic break patterns
- Progressive destruction
Stress-Based Breaking
- Monitor forces on objects
- Break when stress exceeds threshold
- Realistic structural failure
- Joints break under load
Material-Based Destruction
- Different patterns for different materials
- Glass shatters, wood splinters
- Metal deforms then breaks
- Contextual destruction behavior
Related Skills
When users need information about:
- Geometry manipulation - Use unity-physicscore2d-shapes-advanced or unity-physicscore2d-destructor
- Forces and impulses - Use unity-physicscore2d-forces
- Joint breaking - Use unity-physicscore2d-joints
- Collision detection - Use unity-physicscore2d-collision
Worked Examples
All examples below assume the standard PhysicsCore2D OnEnable/OnDisable lifecycle. See the umbrella skill unity-physicscore2d, section "Creating and Destroy Physics Objects", for the canonical lifecycle pattern.
- examples/SlicingPattern.cs — orbiting player fires a slice ray (with optional reflections) into a circular arena; demonstrates
PhysicsDestructor.Slice plus body rebuild with separation impulse.
- examples/FragmentingPattern.cs — top-down shooter that fragments a destructible block on projectile impact via
PhysicsDestructor.Fragment with a circular mask + random seed points; rebuilds an unbroken-remainder body and a debris-body batch, with optional explosion impulse.
- examples/SpriteDestructionPattern.cs — destruct-at-position pattern that splits the unbroken remainder into geometry islands, choosing static vs dynamic per island based on intersection with a virtual ground line.
