unity-physicscore2d-destruction-patterns

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:

• Slicing - https://github.com/Unity-Technologies/PhysicsExamples2D/blob/master/Sandbox/Assets/Examples/Slicing.cs
• Fragmenting - https://github.com/Unity-Technologies/PhysicsExamples2D/blob/master/Sandbox/Assets/Examples/Fragmenting.cs
• SpriteDestruction - https://github.com/Unity-Technologies/PhysicsExamples2D/blob/master/Sandbox/Assets/Examples/SpriteDestruction.cs

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:

1. Detect slice line collision with object
2. Calculate intersection points
3. Generate new polygon geometries
4. Create PhysicsBody for each piece
5. Destroy original body
6. 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.