Collision detection

Collision Detection

UBodySetup

• Contains all the physics data on a single asset (e.g. static mesh)

• Done so that all BodyInstance references can share the physics data/config and not dupe tris everywhere

• Contains FKAggregateGeom that has simplified collision representation of asset

• Typically assets implement GetBodySetup function that's used in physics state creation

Collision:

• Blocking will naturally occur between two objects set to block

• Hit events wont trigger unless Simulation Generates Hit Events is set

• Simulation Generates Hit events doesn't need to be set on both

• Overlap + Generate Overlap events must both be set for overlap events

• Interaction between two objects is min of the flags of both actors. Ex:

• Block + block = block

• [Block + sim generates hit events] + block = Hit Event on 1^st actor + block

• [overlap+ disabled generate overlapevents] + block = nothing

• [overlap + generate overlap events] + block = overlap event on 1^st actor

• After first blocking collision, collision system stops looking for collisions

• Not recommended for object to have generate hit events and overlap events

UE Physics has an async scene + sync scene based on PhysX

• Async means physics computation results can be reported at later frames

• Sync means it runs before all UE4 sim code

• No interdependency calculation between the two

Thread & Sample showing how to update collision at runtime:

• https://wiki.unrealengine.com/Procedural_Mesh_Generation

• https://forums.unrealengine.com/showthread.php?2078-How-to-create-collision-information-for-procedural-geometry

Turn On Drawing For Traces/Geometry Sweeps

• World->DebugDrawTraceTag

• DrawGeomSweeps

• DrawGeomOverlaps

There's a Collision Analyzer Tool for debugging Developer Tools->Collision Analyzer