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911 lines
36 KiB
C#
911 lines
36 KiB
C#
/*
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* Farseer Physics Engine:
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* Copyright (c) 2012 Ian Qvist
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*
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* Original source Box2D:
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* Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
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*
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* This software is provided 'as-is', without any express or implied
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* warranty. In no event will the authors be held liable for any damages
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* arising from the use of this software.
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* Permission is granted to anyone to use this software for any purpose,
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* including commercial applications, and to alter it and redistribute it
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* freely, subject to the following restrictions:
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* 1. The origin of this software must not be misrepresented; you must not
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* claim that you wrote the original software. If you use this software
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* in a product, an acknowledgment in the product documentation would be
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* appreciated but is not required.
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* 2. Altered source versions must be plainly marked as such, and must not be
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* misrepresented as being the original software.
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* 3. This notice may not be removed or altered from any source distribution.
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*/
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using System;
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using System.Numerics;
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using System.Threading;
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using System.Threading.Tasks;
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using Robust.Shared.Maths;
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using Robust.Shared.Physics.Collision;
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using Robust.Shared.Physics.Components;
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using Robust.Shared.Physics.Dynamics;
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using Robust.Shared.Physics.Dynamics.Contacts;
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using Robust.Shared.Utility;
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namespace Robust.Shared.Physics.Systems;
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public abstract partial class SharedPhysicsSystem
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{
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private void ResetSolver(
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in SolverData data,
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in IslandData island,
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ContactVelocityConstraint[] velocityConstraints,
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ContactPositionConstraint[] positionConstraints)
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{
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var contactCount = island.Contacts.Count;
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// Build constraints
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// For now these are going to be bare but will change
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for (var i = 0; i < contactCount; i++)
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{
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var contact = island.Contacts[i];
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Fixture fixtureA = contact.FixtureA!;
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Fixture fixtureB = contact.FixtureB!;
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var shapeA = fixtureA.Shape;
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var shapeB = fixtureB.Shape;
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float radiusA = shapeA.Radius;
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float radiusB = shapeB.Radius;
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var bodyA = contact.BodyA!;
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var bodyB = contact.BodyB!;
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var manifold = contact.Manifold;
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int pointCount = manifold.PointCount;
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DebugTools.Assert(pointCount > 0);
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ref var velocityConstraint = ref velocityConstraints[i];
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velocityConstraint.Friction = contact.Friction;
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velocityConstraint.Restitution = contact.Restitution;
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velocityConstraint.TangentSpeed = contact.TangentSpeed;
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velocityConstraint.IndexA = bodyA.IslandIndex[island.Index];
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velocityConstraint.IndexB = bodyB.IslandIndex[island.Index];
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Array.Resize(ref velocityConstraint.Points, 2);
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// Don't need to reset point data as it all gets set below.
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var (invMassA, invMassB) = GetInvMass(bodyA, bodyB);
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(velocityConstraint.InvMassA, velocityConstraint.InvMassB) = (invMassA, invMassB);
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velocityConstraint.InvIA = bodyA.InvI;
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velocityConstraint.InvIB = bodyB.InvI;
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velocityConstraint.ContactIndex = i;
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velocityConstraint.PointCount = pointCount;
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velocityConstraint.K = System.Numerics.Vector4.Zero;
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velocityConstraint.NormalMass = System.Numerics.Vector4.Zero;
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ref var positionConstraint = ref positionConstraints[i];
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positionConstraint.IndexA = bodyA.IslandIndex[island.Index];
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positionConstraint.IndexB = bodyB.IslandIndex[island.Index];
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(positionConstraint.InvMassA, positionConstraint.InvMassB) = (invMassA, invMassB);
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positionConstraint.LocalCenterA = bodyA.LocalCenter;
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positionConstraint.LocalCenterB = bodyB.LocalCenter;
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Array.Resize(ref positionConstraint.LocalPoints, 2);
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positionConstraint.InvIA = bodyA.InvI;
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positionConstraint.InvIB = bodyB.InvI;
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positionConstraint.LocalNormal = manifold.LocalNormal;
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positionConstraint.LocalPoint = manifold.LocalPoint;
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positionConstraint.PointCount = pointCount;
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positionConstraint.RadiusA = radiusA;
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positionConstraint.RadiusB = radiusB;
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positionConstraint.Type = manifold.Type;
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for (var j = 0; j < pointCount; ++j)
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{
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var contactPoint = manifold.Points[j];
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ref var constraintPoint = ref velocityConstraint.Points[j];
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if (_warmStarting)
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{
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constraintPoint.NormalImpulse = data.DtRatio * contactPoint.NormalImpulse;
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constraintPoint.TangentImpulse = data.DtRatio * contactPoint.TangentImpulse;
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}
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else
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{
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constraintPoint.NormalImpulse = 0.0f;
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constraintPoint.TangentImpulse = 0.0f;
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}
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constraintPoint.RelativeVelocityA = Vector2.Zero;
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constraintPoint.RelativeVelocityB = Vector2.Zero;
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constraintPoint.NormalMass = 0.0f;
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constraintPoint.TangentMass = 0.0f;
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constraintPoint.VelocityBias = 0.0f;
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positionConstraint.LocalPoints[j] = contactPoint.LocalPoint;
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}
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}
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}
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private (float, float) GetInvMass(PhysicsComponent bodyA, PhysicsComponent bodyB)
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{
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// God this is shitcodey but uhhhh we need to snowflake KinematicController for nice collisions.
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// TODO: Might need more finagling with the kinematic bodytype
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switch (bodyA.BodyType)
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{
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case BodyType.Kinematic:
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case BodyType.Static:
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return (bodyA.InvMass, bodyB.InvMass);
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case BodyType.KinematicController:
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switch (bodyB.BodyType)
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{
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case BodyType.Kinematic:
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case BodyType.Static:
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return (bodyA.InvMass, bodyB.InvMass);
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case BodyType.Dynamic:
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return (bodyA.InvMass, 0f);
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case BodyType.KinematicController:
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return (0f, 0f);
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default:
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throw new ArgumentOutOfRangeException();
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}
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case BodyType.Dynamic:
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switch (bodyB.BodyType)
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{
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case BodyType.Kinematic:
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case BodyType.Static:
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case BodyType.Dynamic:
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return (bodyA.InvMass, bodyB.InvMass);
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case BodyType.KinematicController:
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return (0f, bodyB.InvMass);
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default:
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throw new ArgumentOutOfRangeException();
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}
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default:
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throw new ArgumentOutOfRangeException();
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}
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}
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private void InitializeVelocityConstraints(
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in SolverData data,
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in IslandData island,
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ContactVelocityConstraint[] velocityConstraints,
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ContactPositionConstraint[] positionConstraints,
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Vector2[] positions,
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float[] angles,
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Vector2[] linearVelocities,
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float[] angularVelocities)
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{
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Span<Vector2> points = stackalloc Vector2[2];
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var contactCount = island.Contacts.Count;
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var contacts = island.Contacts;
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var offset = island.Offset;
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for (var i = 0; i < contactCount; ++i)
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{
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ref var velocityConstraint = ref velocityConstraints[i];
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var positionConstraint = positionConstraints[i];
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var radiusA = positionConstraint.RadiusA;
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var radiusB = positionConstraint.RadiusB;
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var manifold = contacts[velocityConstraint.ContactIndex].Manifold;
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var indexA = velocityConstraint.IndexA;
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var indexB = velocityConstraint.IndexB;
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var invMassA = velocityConstraint.InvMassA;
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var invMassB = velocityConstraint.InvMassB;
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var invIA = velocityConstraint.InvIA;
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var invIB = velocityConstraint.InvIB;
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var localCenterA = positionConstraint.LocalCenterA;
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var localCenterB = positionConstraint.LocalCenterB;
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var centerA = positions[indexA];
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var angleA = angles[indexA];
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var linVelocityA = linearVelocities[offset + indexA];
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var angVelocityA = angularVelocities[offset + indexA];
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var centerB = positions[indexB];
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var angleB = angles[indexB];
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var linVelocityB = linearVelocities[offset + indexB];
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var angVelocityB = angularVelocities[offset + indexB];
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DebugTools.Assert(manifold.PointCount > 0);
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var xfA = new Transform(angleA);
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var xfB = new Transform(angleB);
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xfA.Position = centerA - Physics.Transform.Mul(xfA.Quaternion2D, localCenterA);
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xfB.Position = centerB - Physics.Transform.Mul(xfB.Quaternion2D, localCenterB);
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InitializeManifold(ref manifold, xfA, xfB, radiusA, radiusB, out var normal, points);
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velocityConstraint.Normal = normal;
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int pointCount = velocityConstraint.PointCount;
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for (int j = 0; j < pointCount; ++j)
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{
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ref var vcp = ref velocityConstraint.Points[j];
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vcp.RelativeVelocityA = points[j] - centerA;
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vcp.RelativeVelocityB = points[j] - centerB;
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float rnA = Vector2Helpers.Cross(vcp.RelativeVelocityA, velocityConstraint.Normal);
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float rnB = Vector2Helpers.Cross(vcp.RelativeVelocityB, velocityConstraint.Normal);
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float kNormal = invMassA + invMassB + invIA * rnA * rnA + invIB * rnB * rnB;
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vcp.NormalMass = kNormal > 0.0f ? 1.0f / kNormal : 0.0f;
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Vector2 tangent = Vector2Helpers.Cross(velocityConstraint.Normal, 1.0f);
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float rtA = Vector2Helpers.Cross(vcp.RelativeVelocityA, tangent);
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float rtB = Vector2Helpers.Cross(vcp.RelativeVelocityB, tangent);
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float kTangent = invMassA + invMassB + invIA * rtA * rtA + invIB * rtB * rtB;
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vcp.TangentMass = kTangent > 0.0f ? 1.0f / kTangent : 0.0f;
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// Setup a velocity bias for restitution.
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vcp.VelocityBias = 0.0f;
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float vRel = Vector2.Dot(velocityConstraint.Normal, linVelocityB + Vector2Helpers.Cross(angVelocityB, vcp.RelativeVelocityB) - linVelocityA - Vector2Helpers.Cross(angVelocityA, vcp.RelativeVelocityA));
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if (vRel < -data.VelocityThreshold)
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{
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vcp.VelocityBias = -velocityConstraint.Restitution * vRel;
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}
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}
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// If we have two points, then prepare the block solver.
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if (velocityConstraint.PointCount == 2)
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{
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var vcp1 = velocityConstraint.Points[0];
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var vcp2 = velocityConstraint.Points[1];
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var rn1A = Vector2Helpers.Cross(vcp1.RelativeVelocityA, velocityConstraint.Normal);
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var rn1B = Vector2Helpers.Cross(vcp1.RelativeVelocityB, velocityConstraint.Normal);
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var rn2A = Vector2Helpers.Cross(vcp2.RelativeVelocityA, velocityConstraint.Normal);
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var rn2B = Vector2Helpers.Cross(vcp2.RelativeVelocityB, velocityConstraint.Normal);
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var k11 = invMassA + invMassB + invIA * rn1A * rn1A + invIB * rn1B * rn1B;
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var k22 = invMassA + invMassB + invIA * rn2A * rn2A + invIB * rn2B * rn2B;
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var k12 = invMassA + invMassB + invIA * rn1A * rn2A + invIB * rn1B * rn2B;
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// Ensure a reasonable condition number.
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const float k_maxConditionNumber = 1000.0f;
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if (k11 * k11 < k_maxConditionNumber * (k11 * k22 - k12 * k12))
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{
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// K is safe to invert.
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velocityConstraint.K = new System.Numerics.Vector4(k11, k12, k12, k22);
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velocityConstraint.NormalMass = Vector4Helpers.Inverse(velocityConstraint.K);
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}
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else
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{
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// The constraints are redundant, just use one.
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// TODO_ERIN use deepest?
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velocityConstraint.PointCount = 1;
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}
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}
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}
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}
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private void WarmStart(
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in SolverData data,
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in IslandData island,
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ContactVelocityConstraint[] velocityConstraints,
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Vector2[] linearVelocities,
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float[] angularVelocities)
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{
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var offset = island.Offset;
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for (var i = 0; i < island.Contacts.Count; ++i)
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{
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var velocityConstraint = velocityConstraints[i];
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var indexA = velocityConstraint.IndexA;
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var indexB = velocityConstraint.IndexB;
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var invMassA = velocityConstraint.InvMassA;
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var invIA = velocityConstraint.InvIA;
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var invMassB = velocityConstraint.InvMassB;
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var invIB = velocityConstraint.InvIB;
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var pointCount = velocityConstraint.PointCount;
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ref var linVelocityA = ref linearVelocities[offset + indexA];
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ref var angVelocityA = ref angularVelocities[offset + indexA];
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ref var linVelocityB = ref linearVelocities[offset + indexB];
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ref var angVelocityB = ref angularVelocities[offset + indexB];
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var normal = velocityConstraint.Normal;
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var tangent = Vector2Helpers.Cross(normal, 1.0f);
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for (var j = 0; j < pointCount; ++j)
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{
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var constraintPoint = velocityConstraint.Points[j];
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var P = normal * constraintPoint.NormalImpulse + tangent * constraintPoint.TangentImpulse;
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angVelocityA -= invIA * Vector2Helpers.Cross(constraintPoint.RelativeVelocityA, P);
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linVelocityA -= P * invMassA;
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angVelocityB += invIB * Vector2Helpers.Cross(constraintPoint.RelativeVelocityB, P);
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linVelocityB += P * invMassB;
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}
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}
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}
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private void SolveVelocityConstraints(IslandData island,
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ParallelOptions? options,
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ContactVelocityConstraint[] velocityConstraints,
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Vector2[] linearVelocities,
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float[] angularVelocities)
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{
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var contactCount = island.Contacts.Count;
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if (options != null && contactCount > VelocityConstraintsPerThread * 2)
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{
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var batches = (int) Math.Ceiling((float) contactCount / VelocityConstraintsPerThread);
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Parallel.For(0, batches, options, i =>
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{
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var start = i * VelocityConstraintsPerThread;
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var end = Math.Min(start + VelocityConstraintsPerThread, contactCount);
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SolveVelocityConstraints(island, start, end, velocityConstraints, linearVelocities, angularVelocities);
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});
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}
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else
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{
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SolveVelocityConstraints(island, 0, contactCount, velocityConstraints, linearVelocities, angularVelocities);
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}
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}
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private void SolveVelocityConstraints(
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IslandData island,
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int start,
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int end,
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ContactVelocityConstraint[] velocityConstraints,
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Vector2[] linearVelocities,
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float[] angularVelocities)
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{
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var offset = island.Offset;
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// Here be dragons
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for (var i = start; i < end; ++i)
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{
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ref var velocityConstraint = ref velocityConstraints[i];
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var indexA = velocityConstraint.IndexA;
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var indexB = velocityConstraint.IndexB;
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var mA = velocityConstraint.InvMassA;
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var iA = velocityConstraint.InvIA;
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var mB = velocityConstraint.InvMassB;
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var iB = velocityConstraint.InvIB;
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var pointCount = velocityConstraint.PointCount;
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ref var vA = ref linearVelocities[offset + indexA];
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ref var wA = ref angularVelocities[offset + indexA];
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ref var vB = ref linearVelocities[offset + indexB];
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ref var wB = ref angularVelocities[offset + indexB];
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var normal = velocityConstraint.Normal;
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var tangent = Vector2Helpers.Cross(normal, 1.0f);
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var friction = velocityConstraint.Friction;
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DebugTools.Assert(pointCount is 1 or 2);
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// Solve tangent constraints first because non-penetration is more important
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// than friction.
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for (var j = 0; j < pointCount; ++j)
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{
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ref var velConstraintPoint = ref velocityConstraint.Points[j];
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// Relative velocity at contact
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var dv = vB + Vector2Helpers.Cross(wB, velConstraintPoint.RelativeVelocityB) - vA - Vector2Helpers.Cross(wA, velConstraintPoint.RelativeVelocityA);
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// Compute tangent force
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float vt = Vector2.Dot(dv, tangent) - velocityConstraint.TangentSpeed;
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float lambda = velConstraintPoint.TangentMass * (-vt);
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// b2Clamp the accumulated force
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var maxFriction = friction * velConstraintPoint.NormalImpulse;
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var newImpulse = Math.Clamp(velConstraintPoint.TangentImpulse + lambda, -maxFriction, maxFriction);
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lambda = newImpulse - velConstraintPoint.TangentImpulse;
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velConstraintPoint.TangentImpulse = newImpulse;
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// Apply contact impulse
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Vector2 P = tangent * lambda;
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vA -= P * mA;
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wA -= iA * Vector2Helpers.Cross(velConstraintPoint.RelativeVelocityA, P);
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vB += P * mB;
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wB += iB * Vector2Helpers.Cross(velConstraintPoint.RelativeVelocityB, P);
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}
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// Solve normal constraints
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if (velocityConstraint.PointCount == 1)
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{
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ref var vcp = ref velocityConstraint.Points[0];
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// Relative velocity at contact
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Vector2 dv = vB + Vector2Helpers.Cross(wB, vcp.RelativeVelocityB) - vA - Vector2Helpers.Cross(wA, vcp.RelativeVelocityA);
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// Compute normal impulse
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float vn = Vector2.Dot(dv, normal);
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float lambda = -vcp.NormalMass * (vn - vcp.VelocityBias);
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// b2Clamp the accumulated impulse
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float newImpulse = Math.Max(vcp.NormalImpulse + lambda, 0.0f);
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lambda = newImpulse - vcp.NormalImpulse;
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vcp.NormalImpulse = newImpulse;
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// Apply contact impulse
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Vector2 P = normal * lambda;
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vA -= P * mA;
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wA -= iA * Vector2Helpers.Cross(vcp.RelativeVelocityA, P);
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vB += P * mB;
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wB += iB * Vector2Helpers.Cross(vcp.RelativeVelocityB, P);
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}
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else
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{
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// Block solver developed in collaboration with Dirk Gregorius (back in 01/07 on Box2D_Lite).
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// Build the mini LCP for this contact patch
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//
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// vn = A * x + b, vn >= 0, , vn >= 0, x >= 0 and vn_i * x_i = 0 with i = 1..2
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//
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// A = J * W * JT and J = ( -n, -r1 x n, n, r2 x n )
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// b = vn0 - velocityBias
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//
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// The system is solved using the "Total enumeration method" (s. Murty). The complementary constraint vn_i * x_i
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// implies that we must have in any solution either vn_i = 0 or x_i = 0. So for the 2D contact problem the cases
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// vn1 = 0 and vn2 = 0, x1 = 0 and x2 = 0, x1 = 0 and vn2 = 0, x2 = 0 and vn1 = 0 need to be tested. The first valid
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// solution that satisfies the problem is chosen.
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//
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// In order to account of the accumulated impulse 'a' (because of the iterative nature of the solver which only requires
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// that the accumulated impulse is clamped and not the incremental impulse) we change the impulse variable (x_i).
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//
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// Substitute:
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//
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// x = a + d
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//
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// a := old total impulse
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// x := new total impulse
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// d := incremental impulse
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//
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// For the current iteration we extend the formula for the incremental impulse
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// to compute the new total impulse:
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//
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// vn = A * d + b
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// = A * (x - a) + b
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// = A * x + b - A * a
|
|
// = A * x + b'
|
|
// b' = b - A * a;
|
|
|
|
ref var cp1 = ref velocityConstraint.Points[0];
|
|
ref var cp2 = ref velocityConstraint.Points[1];
|
|
|
|
Vector2 a = new Vector2(cp1.NormalImpulse, cp2.NormalImpulse);
|
|
DebugTools.Assert(a.X >= 0.0f && a.Y >= 0.0f);
|
|
|
|
// Relative velocity at contact
|
|
Vector2 dv1 = vB + Vector2Helpers.Cross(wB, cp1.RelativeVelocityB) - vA - Vector2Helpers.Cross(wA, cp1.RelativeVelocityA);
|
|
Vector2 dv2 = vB + Vector2Helpers.Cross(wB, cp2.RelativeVelocityB) - vA - Vector2Helpers.Cross(wA, cp2.RelativeVelocityA);
|
|
|
|
// Compute normal velocity
|
|
float vn1 = Vector2.Dot(dv1, normal);
|
|
float vn2 = Vector2.Dot(dv2, normal);
|
|
|
|
Vector2 b = new Vector2
|
|
{
|
|
X = vn1 - cp1.VelocityBias,
|
|
Y = vn2 - cp2.VelocityBias
|
|
};
|
|
|
|
// Compute b'
|
|
b -= Physics.Transform.Mul(velocityConstraint.K, a);
|
|
|
|
//const float k_errorTol = 1e-3f;
|
|
//B2_NOT_USED(k_errorTol);
|
|
|
|
for (; ; )
|
|
{
|
|
//
|
|
// Case 1: vn = 0
|
|
//
|
|
// 0 = A * x + b'
|
|
//
|
|
// Solve for x:
|
|
//
|
|
// x = - inv(A) * b'
|
|
//
|
|
Vector2 x = -Physics.Transform.Mul(velocityConstraint.NormalMass, b);
|
|
|
|
if (x.X >= 0.0f && x.Y >= 0.0f)
|
|
{
|
|
// Get the incremental impulse
|
|
Vector2 d = x - a;
|
|
|
|
// Apply incremental impulse
|
|
Vector2 P1 = normal * d.X;
|
|
Vector2 P2 = normal * d.Y;
|
|
vA -= (P1 + P2) * mA;
|
|
wA -= iA * (Vector2Helpers.Cross(cp1.RelativeVelocityA, P1) + Vector2Helpers.Cross(cp2.RelativeVelocityA, P2));
|
|
|
|
vB += (P1 + P2) * mB;
|
|
wB += iB * (Vector2Helpers.Cross(cp1.RelativeVelocityB, P1) + Vector2Helpers.Cross(cp2.RelativeVelocityB, P2));
|
|
|
|
// Accumulate
|
|
cp1.NormalImpulse = x.X;
|
|
cp2.NormalImpulse = x.Y;
|
|
|
|
break;
|
|
}
|
|
|
|
//
|
|
// Case 2: vn1 = 0 and x2 = 0
|
|
//
|
|
// 0 = a11 * x1 + a12 * 0 + b1'
|
|
// vn2 = a21 * x1 + a22 * 0 + b2'
|
|
//
|
|
x.X = -cp1.NormalMass * b.X;
|
|
x.Y = 0.0f;
|
|
vn1 = 0.0f;
|
|
vn2 = velocityConstraint.K.Y * x.X + b.Y;
|
|
|
|
if (x.X >= 0.0f && vn2 >= 0.0f)
|
|
{
|
|
// Get the incremental impulse
|
|
Vector2 d = x - a;
|
|
|
|
// Apply incremental impulse
|
|
Vector2 P1 = normal * d.X;
|
|
Vector2 P2 = normal * d.Y;
|
|
vA -= (P1 + P2) * mA;
|
|
wA -= iA * (Vector2Helpers.Cross(cp1.RelativeVelocityA, P1) + Vector2Helpers.Cross(cp2.RelativeVelocityA, P2));
|
|
|
|
vB += (P1 + P2) * mB;
|
|
wB += iB * (Vector2Helpers.Cross(cp1.RelativeVelocityB, P1) + Vector2Helpers.Cross(cp2.RelativeVelocityB, P2));
|
|
|
|
// Accumulate
|
|
cp1.NormalImpulse = x.X;
|
|
cp2.NormalImpulse = x.Y;
|
|
|
|
break;
|
|
}
|
|
|
|
|
|
//
|
|
// Case 3: vn2 = 0 and x1 = 0
|
|
//
|
|
// vn1 = a11 * 0 + a12 * x2 + b1'
|
|
// 0 = a21 * 0 + a22 * x2 + b2'
|
|
//
|
|
x.X = 0.0f;
|
|
x.Y = -cp2.NormalMass * b.Y;
|
|
vn1 = velocityConstraint.K.Z * x.Y + b.X;
|
|
vn2 = 0.0f;
|
|
|
|
if (x.Y >= 0.0f && vn1 >= 0.0f)
|
|
{
|
|
// Resubstitute for the incremental impulse
|
|
Vector2 d = x - a;
|
|
|
|
// Apply incremental impulse
|
|
Vector2 P1 = normal * d.X;
|
|
Vector2 P2 = normal * d.Y;
|
|
vA -= (P1 + P2) * mA;
|
|
wA -= iA * (Vector2Helpers.Cross(cp1.RelativeVelocityA, P1) + Vector2Helpers.Cross(cp2.RelativeVelocityA, P2));
|
|
|
|
vB += (P1 + P2) * mB;
|
|
wB += iB * (Vector2Helpers.Cross(cp1.RelativeVelocityB, P1) + Vector2Helpers.Cross(cp2.RelativeVelocityB, P2));
|
|
|
|
// Accumulate
|
|
cp1.NormalImpulse = x.X;
|
|
cp2.NormalImpulse = x.Y;
|
|
|
|
break;
|
|
}
|
|
|
|
//
|
|
// Case 4: x1 = 0 and x2 = 0
|
|
//
|
|
// vn1 = b1
|
|
// vn2 = b2;
|
|
x.X = 0.0f;
|
|
x.Y = 0.0f;
|
|
vn1 = b.X;
|
|
vn2 = b.Y;
|
|
|
|
if (vn1 >= 0.0f && vn2 >= 0.0f)
|
|
{
|
|
// Resubstitute for the incremental impulse
|
|
Vector2 d = x - a;
|
|
|
|
// Apply incremental impulse
|
|
Vector2 P1 = normal * d.X;
|
|
Vector2 P2 = normal * d.Y;
|
|
vA -= (P1 + P2) * mA;
|
|
wA -= iA * (Vector2Helpers.Cross(cp1.RelativeVelocityA, P1) + Vector2Helpers.Cross(cp2.RelativeVelocityA, P2));
|
|
|
|
vB += (P1 + P2) * mB;
|
|
wB += iB * (Vector2Helpers.Cross(cp1.RelativeVelocityB, P1) + Vector2Helpers.Cross(cp2.RelativeVelocityB, P2));
|
|
|
|
// Accumulate
|
|
cp1.NormalImpulse = x.X;
|
|
cp2.NormalImpulse = x.Y;
|
|
|
|
break;
|
|
}
|
|
|
|
// No solution, give up. This is hit sometimes, but it doesn't seem to matter.
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
private void StoreImpulses(in IslandData island, ContactVelocityConstraint[] velocityConstraints)
|
|
{
|
|
for (var i = 0; i < island.Contacts.Count; ++i)
|
|
{
|
|
ContactVelocityConstraint velocityConstraint = velocityConstraints[i];
|
|
ref var manifold = ref island.Contacts[velocityConstraint.ContactIndex].Manifold;
|
|
|
|
for (var j = 0; j < velocityConstraint.PointCount; ++j)
|
|
{
|
|
ref var point = ref manifold.Points[j];
|
|
point.NormalImpulse = velocityConstraint.Points[j].NormalImpulse;
|
|
point.TangentImpulse = velocityConstraint.Points[j].TangentImpulse;
|
|
}
|
|
}
|
|
}
|
|
|
|
private bool SolvePositionConstraints(
|
|
SolverData data,
|
|
in IslandData island,
|
|
ParallelOptions? options,
|
|
ContactPositionConstraint[] positionConstraints,
|
|
Vector2[] positions,
|
|
float[] angles)
|
|
{
|
|
var contactCount = island.Contacts.Count;
|
|
|
|
// Parallel
|
|
if (options != null && contactCount > PositionConstraintsPerThread * 2)
|
|
{
|
|
var unsolved = 0;
|
|
var batches = (int) Math.Ceiling((float) contactCount / PositionConstraintsPerThread);
|
|
|
|
Parallel.For(0, batches, options, i =>
|
|
{
|
|
var start = i * PositionConstraintsPerThread;
|
|
var end = Math.Min(start + PositionConstraintsPerThread, contactCount);
|
|
|
|
if (!SolvePositionConstraints(data, start, end, positionConstraints, positions, angles))
|
|
Interlocked.Increment(ref unsolved);
|
|
});
|
|
|
|
return unsolved == 0;
|
|
}
|
|
|
|
// No parallel
|
|
return SolvePositionConstraints(data, 0, contactCount, positionConstraints, positions, angles);
|
|
}
|
|
|
|
/// <summary>
|
|
/// Tries to solve positions for all contacts specified.
|
|
/// </summary>
|
|
/// <returns>true if all positions solved</returns>
|
|
private bool SolvePositionConstraints(
|
|
SolverData data,
|
|
int start,
|
|
int end,
|
|
ContactPositionConstraint[] positionConstraints,
|
|
Vector2[] positions,
|
|
float[] angles)
|
|
{
|
|
float minSeparation = 0.0f;
|
|
|
|
for (int i = start; i < end; ++i)
|
|
{
|
|
var pc = positionConstraints[i];
|
|
|
|
int indexA = pc.IndexA;
|
|
int indexB = pc.IndexB;
|
|
Vector2 localCenterA = pc.LocalCenterA;
|
|
float mA = pc.InvMassA;
|
|
float iA = pc.InvIA;
|
|
Vector2 localCenterB = pc.LocalCenterB;
|
|
float mB = pc.InvMassB;
|
|
float iB = pc.InvIB;
|
|
int pointCount = pc.PointCount;
|
|
|
|
ref var centerA = ref positions[indexA];
|
|
ref var angleA = ref angles[indexA];
|
|
ref var centerB = ref positions[indexB];
|
|
ref var angleB = ref angles[indexB];
|
|
|
|
// Solve normal constraints
|
|
for (int j = 0; j < pointCount; ++j)
|
|
{
|
|
Transform xfA = new Transform(angleA);
|
|
Transform xfB = new Transform(angleB);
|
|
xfA.Position = centerA - Physics.Transform.Mul(xfA.Quaternion2D, localCenterA);
|
|
xfB.Position = centerB - Physics.Transform.Mul(xfB.Quaternion2D, localCenterB);
|
|
|
|
Vector2 normal;
|
|
Vector2 point;
|
|
float separation;
|
|
|
|
PositionSolverManifoldInitialize(pc, j, xfA, xfB, out normal, out point, out separation);
|
|
|
|
Vector2 rA = point - centerA;
|
|
Vector2 rB = point - centerB;
|
|
|
|
// Track max constraint error.
|
|
minSeparation = Math.Min(minSeparation, separation);
|
|
|
|
// Prevent large corrections and allow slop.
|
|
float C = Math.Clamp(data.Baumgarte * (separation + PhysicsConstants.LinearSlop), -_maxLinearCorrection, 0.0f);
|
|
|
|
// Compute the effective mass.
|
|
float rnA = Vector2Helpers.Cross(rA, normal);
|
|
float rnB = Vector2Helpers.Cross(rB, normal);
|
|
float K = mA + mB + iA * rnA * rnA + iB * rnB * rnB;
|
|
|
|
// Compute normal impulse
|
|
float impulse = K > 0.0f ? -C / K : 0.0f;
|
|
|
|
Vector2 P = normal * impulse;
|
|
|
|
centerA -= P * mA;
|
|
angleA -= iA * Vector2Helpers.Cross(rA, P);
|
|
|
|
centerB += P * mB;
|
|
angleB += iB * Vector2Helpers.Cross(rB, P);
|
|
}
|
|
}
|
|
|
|
// We can't expect minSpeparation >= -b2_linearSlop because we don't
|
|
// push the separation above -b2_linearSlop.
|
|
return minSeparation >= -3.0f * PhysicsConstants.LinearSlop;
|
|
}
|
|
|
|
/// <summary>
|
|
/// Evaluate the manifold with supplied transforms. This assumes
|
|
/// modest motion from the original state. This does not change the
|
|
/// point count, impulses, etc. The radii must come from the Shapes
|
|
/// that generated the manifold.
|
|
/// </summary>
|
|
internal static void InitializeManifold(
|
|
ref Manifold manifold,
|
|
in Transform xfA,
|
|
in Transform xfB,
|
|
float radiusA,
|
|
float radiusB,
|
|
out Vector2 normal,
|
|
Span<Vector2> points)
|
|
{
|
|
normal = Vector2.Zero;
|
|
|
|
if (manifold.PointCount == 0)
|
|
{
|
|
return;
|
|
}
|
|
|
|
switch (manifold.Type)
|
|
{
|
|
case ManifoldType.Circles:
|
|
{
|
|
normal = new Vector2(1.0f, 0.0f);
|
|
Vector2 pointA = Physics.Transform.Mul(xfA, manifold.LocalPoint);
|
|
Vector2 pointB = Physics.Transform.Mul(xfB, manifold.Points[0].LocalPoint);
|
|
|
|
if ((pointA - pointB).LengthSquared() > float.Epsilon * float.Epsilon)
|
|
{
|
|
normal = pointB - pointA;
|
|
normal = normal.Normalized();
|
|
}
|
|
|
|
Vector2 cA = pointA + normal * radiusA;
|
|
Vector2 cB = pointB - normal * radiusB;
|
|
points[0] = (cA + cB) * 0.5f;
|
|
}
|
|
break;
|
|
|
|
case ManifoldType.FaceA:
|
|
{
|
|
normal = Physics.Transform.Mul(xfA.Quaternion2D, manifold.LocalNormal);
|
|
Vector2 planePoint = Physics.Transform.Mul(xfA, manifold.LocalPoint);
|
|
|
|
for (int i = 0; i < manifold.PointCount; ++i)
|
|
{
|
|
Vector2 clipPoint = Physics.Transform.Mul(xfB, manifold.Points[i].LocalPoint);
|
|
Vector2 cA = clipPoint + normal * (radiusA - Vector2.Dot(clipPoint - planePoint, normal));
|
|
Vector2 cB = clipPoint - normal * radiusB;
|
|
points[i] = (cA + cB) * 0.5f;
|
|
}
|
|
}
|
|
break;
|
|
|
|
case ManifoldType.FaceB:
|
|
{
|
|
normal = Physics.Transform.Mul(xfB.Quaternion2D, manifold.LocalNormal);
|
|
Vector2 planePoint = Physics.Transform.Mul(xfB, manifold.LocalPoint);
|
|
|
|
for (int i = 0; i < manifold.PointCount; ++i)
|
|
{
|
|
Vector2 clipPoint = Physics.Transform.Mul(xfA, manifold.Points[i].LocalPoint);
|
|
Vector2 cB = clipPoint + normal * (radiusB - Vector2.Dot(clipPoint - planePoint, normal));
|
|
Vector2 cA = clipPoint - normal * radiusA;
|
|
points[i] = (cA + cB) * 0.5f;
|
|
}
|
|
|
|
// Ensure normal points from A to B.
|
|
normal = -normal;
|
|
}
|
|
break;
|
|
default:
|
|
// Shouldn't happentm
|
|
throw new InvalidOperationException();
|
|
|
|
}
|
|
}
|
|
|
|
private static void PositionSolverManifoldInitialize(
|
|
in ContactPositionConstraint pc,
|
|
int index,
|
|
in Transform xfA,
|
|
in Transform xfB,
|
|
out Vector2 normal,
|
|
out Vector2 point,
|
|
out float separation)
|
|
{
|
|
DebugTools.Assert(pc.PointCount > 0);
|
|
|
|
switch (pc.Type)
|
|
{
|
|
case ManifoldType.Circles:
|
|
{
|
|
Vector2 pointA = Physics.Transform.Mul(xfA, pc.LocalPoint);
|
|
Vector2 pointB = Physics.Transform.Mul(xfB, pc.LocalPoints[0]);
|
|
normal = pointB - pointA;
|
|
|
|
//FPE: Fix to handle zero normalization
|
|
if (normal != Vector2.Zero)
|
|
normal = normal.Normalized();
|
|
|
|
point = (pointA + pointB) * 0.5f;
|
|
separation = Vector2.Dot(pointB - pointA, normal) - pc.RadiusA - pc.RadiusB;
|
|
}
|
|
break;
|
|
|
|
case ManifoldType.FaceA:
|
|
{
|
|
normal = Physics.Transform.Mul(xfA.Quaternion2D, pc.LocalNormal);
|
|
Vector2 planePoint = Physics.Transform.Mul(xfA, pc.LocalPoint);
|
|
|
|
Vector2 clipPoint = Physics.Transform.Mul(xfB, pc.LocalPoints[index]);
|
|
separation = Vector2.Dot(clipPoint - planePoint, normal) - pc.RadiusA - pc.RadiusB;
|
|
point = clipPoint;
|
|
}
|
|
break;
|
|
|
|
case ManifoldType.FaceB:
|
|
{
|
|
normal = Physics.Transform.Mul(xfB.Quaternion2D, pc.LocalNormal);
|
|
Vector2 planePoint = Physics.Transform.Mul(xfB, pc.LocalPoint);
|
|
|
|
Vector2 clipPoint = Physics.Transform.Mul(xfA, pc.LocalPoints[index]);
|
|
separation = Vector2.Dot(clipPoint - planePoint, normal) - pc.RadiusA - pc.RadiusB;
|
|
point = clipPoint;
|
|
|
|
// Ensure normal points from A to B
|
|
normal = -normal;
|
|
}
|
|
break;
|
|
default:
|
|
normal = Vector2.Zero;
|
|
point = Vector2.Zero;
|
|
separation = 0;
|
|
break;
|
|
|
|
}
|
|
}
|
|
}
|