PowerPoint Presentation
Physics and features in 2D and 3DMorten Skaaning@ Physics
Team
Performance tipsFeatures
2D Physics
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Colliders are mostly immutable.Prefer to setup once (or be aware
of cost)
Static CollidersOne shared bodyTransform each vertex of a
modified ColliderRigidbody2D.isKinematic if moved2D Physics -
Performance
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Modifying Transform on Rigidbody2D
Changing PositionRebuilds contact points if RB is on
GO.Recreates all Colliders if GO is child of RB.
Changing Rotation or Scale (or Size or Radius)Recreates
Colliders!
2D Physics - Performance
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Use NonAlloc queries to avoid garbage collection.
User-prepared fixed-size results container
LinecastNonAlloc, RaycastNonAlloc, GetRayIntersectionNonAlloc,
CircleCastNonAlloc, BoxCastNonAlloc, OverlapPointNonAlloc,
OverlapCircleNonAlloc, OverlapAreaNonAlloc
2D Physics - Performance
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From 5.0 fast knowledge of touching Colliders.
IsTouchingIsTouchingLayers
Both are available on Physics2D, Collider2D & Rigidbody2D2D
Physics - Performance
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From 5.1Freeze PositionFreeze RotationAvoid locking all DoFs2D
Physics - Constraints
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FixedJoint2DFixes two Rigidbody2D together w. configurable
spring2D Physics - New in 5.3
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RelativeJoint2DKeeps two Rigidbody2D at their relative
orientation using configurable maximum linear/angular forcesMore
like motor than spring2D Physics - New in 5.3
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TargetJoint2DSingle Rigidbody2DMoves the Rigidbody2D to Target
position using configurable spring2D Physics - New in 5.3
Will move a rigid-body to a target position using a configurable
maximum force and spring. It is the only joint which operates on a
single rigid-body10
FrictionJoint2DApplies force and torque to reduce linear and
angular velocities to zero2D Physics - New in 5.3
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BuoyancyEffector2DApplies buoyancy, fluid-flow and drag forces
to simulate fluid behavior.2D Physics - New in 5.3
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Demo time
2D Physics - New in 5.3
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3D PhysicsFixing joint issuesFeaturesFuture
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Static Colliders (without Rigidbody)Does not simulate movement
properlyUse Rigidbody w. isKinematic=true
Moving kinematic RigidbodiesSet Transform directly = teleportUse
MovePosition(), MoveRotation(), Move() to impart velocity3D Physics
General Rigidbody stuff
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Fast moving RigidbodiesRigidbodies using Freeze
RotationRagdolls3D Physics Joint issues
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Fast moving Rigidbodies (1)
PhysX: One FixedUpdate delay: Contact discovered vs
resolvedEnable Continuous Collision Detection (CCD)Increase contact
offsetglobally: Physics.contactOffsetper-collider:
Collider.contactOffset=> increases radius of ColliderCan change
collision behavior slightly3D Physics Joint issues
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Fast moving Rigidbodies (2)
Ragdoll? Convert to ragdoll earlierContinuous Collision
Detection (CCD) enabled Rigidbodies ignore joints on high-speed
impacts3D Physics Joint issues
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Rigidbodies using Freeze Rotation (1)
Implemented as infinite inertiaWorks in local space!Can cause
explosions:Switch off preprocessingJoint.enablePreprocessing =
false
3D Physics Joint issues
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Rigidbodies using Freeze Rotation (2)
Sliding when stackedIncrease Solver Iteration CountTry around 20
iterationsVery small perf impact
3D Physics Joint issues
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Rigidbodies using Freeze Rotation (3)
Combining 2+ Freeze Rotation and HingeJoint currently makes
PhysX crashPlease avoid Probably unneeded anyways
3D Physics Joint issues
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Ragdolls (1)
All body parts should have about equal massAvoid small joint
limit spans. Min 5 to 15 degree span.In extreme conditions, enable
projectionhelps to keep limbs tightlinear & rotational
projectionJoint.enableProjection = truebe careful with kinematics
Rigidbodies
3D Physics Joint issues
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Ragdolls (2)
In tight aiming sub-machine gun posesTry reducing Collider
radius/sizeTry making the Joint limits widerTry lowering
Rigidbody.maxDepenetrationVelocity
3D Physics Joint issues
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Ragdolls (3)
Jitter: Try increasing Solver Iteration CountTry around 20Avoid
setting body part TransformUse MovePosition, MoveRotation, Move
insteadAvoid exotic scaling on body/jointNegative = badAll ones for
debug3D Physics Joint issues
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DocsJoint and ragdoll
stabilityhttp://docs.unity3d.com/Manual/RagdollStability.htmlUpgrade
guide from
Unity4http://docs.unity3d.com/Manual/UpgradeGuide5-Physics.html
3D Physics Online resources
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Expose Collision.impulseSum of impulse in first 16 contacts in
Collider-Collider pair
public class Foo : MonoBehaviour {public void
OnCollisionEnter(Collision collision) {Debug.Log(Collision impulse:
+ collision.impulse);}}
Collision callbacks needs more work to expose each contact
without GC
3D Physics New in 5.2
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Per call control of trigger / raycast interaction
enum Physics.QueryTriggerInteractionUseGlobal IgnoreCollide3D
Physics New in 5.2
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Oriented box queries!
Physics.CheckBoxPhysics.OverlapBoxPhysics.BoxCastPhysics.BoxCastAll3D
Physics New in 5.3 (Alpha 4)
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Non garbage allocating queries
RaycastNonAllocBoxCastNonAllocSphereCastNonAllocCapsuleCastNonAllocOverlapSphereNonAllocOverlapBoxNonAlloc3D
Physics New in 5.3 (Alpha 4)
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Mass distribution control
ExplicitRigidbody.centerOfMassRigidbody.inertiaTensorImplicitRigidbody.ResetCenterOfMass()Rigidbody.ResetInertiaTensor()3D
Physics New in 5.3 (Alpha 4)
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WheelCollider scaling support improved
Particles prioritize TerrainColliders over other Colliders
3D Physics New in 5.3 (Alpha 4)
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HingeJoint orientationSame as Unity4Limits, TargetPosition
Rigidbody w. GO(pink)Clockwise/left-hand
Connected Body (grey)Counter-clockwise/right-hand
3D Physics New in 5.3 (Alpha 4)
The Rigidbody that share the GameObject with the HingeJoint will
view the Joint anchor as a left-hand coordinate system. This means
the Rigidbody will view positive angles as going clockwise around
the Joint anchor.
The HingeJoint "Connected Body" will view the Joint anchor as a
right-hand coordinate system. This means the Connected Body will
view positive angles as going counter-clockwise around the Joint
anchor.
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Bugs (most of our time)CharacterController climb
crazinessWheelColliderOnTriggerStay issuesSphereCast on scaled
meshesPhysX on Android devicesRegressions
FeaturesShort term vs long term3D Physics roadmap
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Collision geometry visualization
Overlay on scene view
Support large terrains
Feature set can grow
Plan to release public test this fall3D Physics roadmap
features
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HACD Solve Concave MeshCollider problemConvex
decompositionInitially at import time3D Physics roadmap
features
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PhysX 3.3.3 (from 3.3.1)Collision detection, threading fixes
Further reduce garbage generationChange Collision.contacts to
user-supplied array
Enable PhysX checked errorsEditor/Development only3D Physics
roadmap features
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Questions?
[email protected]
Twitter:morten_skaaningThank you for listening
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