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Rename Box2D folder to box2d
This commit is contained in:
Garrett Brown
@@ -0,0 +1,842 @@
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// MIT License
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// Copyright (c) 2019 Erin Catto
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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// The above copyright notice and this permission notice shall be included in all
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// copies or substantial portions of the Software.
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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// SOFTWARE.
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#include "b2_contact_solver.h"
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#include "box2d/b2_body.h"
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#include "box2d/b2_contact.h"
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#include "box2d/b2_fixture.h"
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#include "box2d/b2_stack_allocator.h"
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#include "box2d/b2_world.h"
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// Solver debugging is normally disabled because the block solver sometimes has to deal with a poorly conditioned effective mass matrix.
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#define B2_DEBUG_SOLVER 0
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bool g_blockSolve = true;
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struct b2ContactPositionConstraint
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{
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b2Vec2 localPoints[b2_maxManifoldPoints];
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b2Vec2 localNormal;
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b2Vec2 localPoint;
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int32 indexA;
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int32 indexB;
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float invMassA, invMassB;
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b2Vec2 localCenterA, localCenterB;
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float invIA, invIB;
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b2Manifold::Type type;
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float radiusA, radiusB;
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int32 pointCount;
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};
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b2ContactSolver::b2ContactSolver(b2ContactSolverDef* def)
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{
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m_step = def->step;
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m_allocator = def->allocator;
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m_count = def->count;
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m_positionConstraints = (b2ContactPositionConstraint*)m_allocator->Allocate(m_count * sizeof(b2ContactPositionConstraint));
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m_velocityConstraints = (b2ContactVelocityConstraint*)m_allocator->Allocate(m_count * sizeof(b2ContactVelocityConstraint));
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m_positions = def->positions;
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m_velocities = def->velocities;
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m_contacts = def->contacts;
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// Initialize position independent portions of the constraints.
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for (int32 i = 0; i < m_count; ++i)
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{
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b2Contact* contact = m_contacts[i];
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b2Fixture* fixtureA = contact->m_fixtureA;
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b2Fixture* fixtureB = contact->m_fixtureB;
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b2Shape* shapeA = fixtureA->GetShape();
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b2Shape* shapeB = fixtureB->GetShape();
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float radiusA = shapeA->m_radius;
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float radiusB = shapeB->m_radius;
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b2Body* bodyA = fixtureA->GetBody();
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b2Body* bodyB = fixtureB->GetBody();
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b2Manifold* manifold = contact->GetManifold();
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int32 pointCount = manifold->pointCount;
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b2Assert(pointCount > 0);
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b2ContactVelocityConstraint* vc = m_velocityConstraints + i;
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vc->friction = contact->m_friction;
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vc->restitution = contact->m_restitution;
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vc->tangentSpeed = contact->m_tangentSpeed;
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vc->indexA = bodyA->m_islandIndex;
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vc->indexB = bodyB->m_islandIndex;
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vc->invMassA = bodyA->m_invMass;
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vc->invMassB = bodyB->m_invMass;
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vc->invIA = bodyA->m_invI;
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vc->invIB = bodyB->m_invI;
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vc->contactIndex = i;
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vc->pointCount = pointCount;
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vc->K.SetZero();
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vc->normalMass.SetZero();
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b2ContactPositionConstraint* pc = m_positionConstraints + i;
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pc->indexA = bodyA->m_islandIndex;
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pc->indexB = bodyB->m_islandIndex;
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pc->invMassA = bodyA->m_invMass;
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pc->invMassB = bodyB->m_invMass;
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pc->localCenterA = bodyA->m_sweep.localCenter;
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pc->localCenterB = bodyB->m_sweep.localCenter;
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pc->invIA = bodyA->m_invI;
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pc->invIB = bodyB->m_invI;
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pc->localNormal = manifold->localNormal;
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pc->localPoint = manifold->localPoint;
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pc->pointCount = pointCount;
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pc->radiusA = radiusA;
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pc->radiusB = radiusB;
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pc->type = manifold->type;
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for (int32 j = 0; j < pointCount; ++j)
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{
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b2ManifoldPoint* cp = manifold->points + j;
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b2VelocityConstraintPoint* vcp = vc->points + j;
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if (m_step.warmStarting)
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{
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vcp->normalImpulse = m_step.dtRatio * cp->normalImpulse;
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vcp->tangentImpulse = m_step.dtRatio * cp->tangentImpulse;
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}
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else
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{
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vcp->normalImpulse = 0.0f;
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vcp->tangentImpulse = 0.0f;
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}
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vcp->rA.SetZero();
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vcp->rB.SetZero();
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vcp->normalMass = 0.0f;
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vcp->tangentMass = 0.0f;
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vcp->velocityBias = 0.0f;
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pc->localPoints[j] = cp->localPoint;
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}
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}
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}
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b2ContactSolver::~b2ContactSolver()
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{
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m_allocator->Free(m_velocityConstraints);
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m_allocator->Free(m_positionConstraints);
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}
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// Initialize position dependent portions of the velocity constraints.
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void b2ContactSolver::InitializeVelocityConstraints()
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{
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for (int32 i = 0; i < m_count; ++i)
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{
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b2ContactVelocityConstraint* vc = m_velocityConstraints + i;
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b2ContactPositionConstraint* pc = m_positionConstraints + i;
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float radiusA = pc->radiusA;
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float radiusB = pc->radiusB;
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b2Manifold* manifold = m_contacts[vc->contactIndex]->GetManifold();
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int32 indexA = vc->indexA;
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int32 indexB = vc->indexB;
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float mA = vc->invMassA;
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float mB = vc->invMassB;
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float iA = vc->invIA;
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float iB = vc->invIB;
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b2Vec2 localCenterA = pc->localCenterA;
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b2Vec2 localCenterB = pc->localCenterB;
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b2Vec2 cA = m_positions[indexA].c;
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float aA = m_positions[indexA].a;
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b2Vec2 vA = m_velocities[indexA].v;
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float wA = m_velocities[indexA].w;
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b2Vec2 cB = m_positions[indexB].c;
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float aB = m_positions[indexB].a;
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b2Vec2 vB = m_velocities[indexB].v;
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float wB = m_velocities[indexB].w;
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b2Assert(manifold->pointCount > 0);
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b2Transform xfA, xfB;
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xfA.q.Set(aA);
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xfB.q.Set(aB);
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xfA.p = cA - b2Mul(xfA.q, localCenterA);
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xfB.p = cB - b2Mul(xfB.q, localCenterB);
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b2WorldManifold worldManifold;
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worldManifold.Initialize(manifold, xfA, radiusA, xfB, radiusB);
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vc->normal = worldManifold.normal;
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int32 pointCount = vc->pointCount;
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for (int32 j = 0; j < pointCount; ++j)
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{
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b2VelocityConstraintPoint* vcp = vc->points + j;
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vcp->rA = worldManifold.points[j] - cA;
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vcp->rB = worldManifold.points[j] - cB;
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float rnA = b2Cross(vcp->rA, vc->normal);
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float rnB = b2Cross(vcp->rB, vc->normal);
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float kNormal = mA + mB + iA * rnA * rnA + iB * rnB * rnB;
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vcp->normalMass = kNormal > 0.0f ? 1.0f / kNormal : 0.0f;
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b2Vec2 tangent = b2Cross(vc->normal, 1.0f);
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float rtA = b2Cross(vcp->rA, tangent);
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float rtB = b2Cross(vcp->rB, tangent);
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float kTangent = mA + mB + iA * rtA * rtA + iB * 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 = b2Dot(vc->normal, vB + b2Cross(wB, vcp->rB) - vA - b2Cross(wA, vcp->rA));
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if (vRel < -b2_velocityThreshold)
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{
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vcp->velocityBias = -vc->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 (vc->pointCount == 2 && g_blockSolve)
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{
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b2VelocityConstraintPoint* vcp1 = vc->points + 0;
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b2VelocityConstraintPoint* vcp2 = vc->points + 1;
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float rn1A = b2Cross(vcp1->rA, vc->normal);
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float rn1B = b2Cross(vcp1->rB, vc->normal);
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float rn2A = b2Cross(vcp2->rA, vc->normal);
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float rn2B = b2Cross(vcp2->rB, vc->normal);
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float k11 = mA + mB + iA * rn1A * rn1A + iB * rn1B * rn1B;
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float k22 = mA + mB + iA * rn2A * rn2A + iB * rn2B * rn2B;
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float k12 = mA + mB + iA * rn1A * rn2A + iB * 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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vc->K.ex.Set(k11, k12);
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vc->K.ey.Set(k12, k22);
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vc->normalMass = vc->K.GetInverse();
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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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vc->pointCount = 1;
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}
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}
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}
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}
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void b2ContactSolver::WarmStart()
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{
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// Warm start.
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for (int32 i = 0; i < m_count; ++i)
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{
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b2ContactVelocityConstraint* vc = m_velocityConstraints + i;
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int32 indexA = vc->indexA;
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int32 indexB = vc->indexB;
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float mA = vc->invMassA;
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float iA = vc->invIA;
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float mB = vc->invMassB;
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float iB = vc->invIB;
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int32 pointCount = vc->pointCount;
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b2Vec2 vA = m_velocities[indexA].v;
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float wA = m_velocities[indexA].w;
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b2Vec2 vB = m_velocities[indexB].v;
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float wB = m_velocities[indexB].w;
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b2Vec2 normal = vc->normal;
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b2Vec2 tangent = b2Cross(normal, 1.0f);
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for (int32 j = 0; j < pointCount; ++j)
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{
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b2VelocityConstraintPoint* vcp = vc->points + j;
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b2Vec2 P = vcp->normalImpulse * normal + vcp->tangentImpulse * tangent;
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wA -= iA * b2Cross(vcp->rA, P);
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vA -= mA * P;
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wB += iB * b2Cross(vcp->rB, P);
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vB += mB * P;
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}
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m_velocities[indexA].v = vA;
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m_velocities[indexA].w = wA;
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m_velocities[indexB].v = vB;
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m_velocities[indexB].w = wB;
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}
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}
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void b2ContactSolver::SolveVelocityConstraints()
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{
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for (int32 i = 0; i < m_count; ++i)
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{
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b2ContactVelocityConstraint* vc = m_velocityConstraints + i;
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int32 indexA = vc->indexA;
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int32 indexB = vc->indexB;
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float mA = vc->invMassA;
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float iA = vc->invIA;
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float mB = vc->invMassB;
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float iB = vc->invIB;
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int32 pointCount = vc->pointCount;
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b2Vec2 vA = m_velocities[indexA].v;
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float wA = m_velocities[indexA].w;
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b2Vec2 vB = m_velocities[indexB].v;
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float wB = m_velocities[indexB].w;
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b2Vec2 normal = vc->normal;
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b2Vec2 tangent = b2Cross(normal, 1.0f);
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float friction = vc->friction;
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b2Assert(pointCount == 1 || pointCount == 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 (int32 j = 0; j < pointCount; ++j)
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{
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b2VelocityConstraintPoint* vcp = vc->points + j;
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// Relative velocity at contact
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b2Vec2 dv = vB + b2Cross(wB, vcp->rB) - vA - b2Cross(wA, vcp->rA);
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// Compute tangent force
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float vt = b2Dot(dv, tangent) - vc->tangentSpeed;
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float lambda = vcp->tangentMass * (-vt);
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// b2Clamp the accumulated force
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float maxFriction = friction * vcp->normalImpulse;
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float newImpulse = b2Clamp(vcp->tangentImpulse + lambda, -maxFriction, maxFriction);
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lambda = newImpulse - vcp->tangentImpulse;
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vcp->tangentImpulse = newImpulse;
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// Apply contact impulse
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b2Vec2 P = lambda * tangent;
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vA -= mA * P;
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wA -= iA * b2Cross(vcp->rA, P);
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vB += mB * P;
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wB += iB * b2Cross(vcp->rB, P);
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}
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// Solve normal constraints
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if (pointCount == 1 || g_blockSolve == false)
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{
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for (int32 j = 0; j < pointCount; ++j)
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{
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b2VelocityConstraintPoint* vcp = vc->points + j;
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// Relative velocity at contact
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b2Vec2 dv = vB + b2Cross(wB, vcp->rB) - vA - b2Cross(wA, vcp->rA);
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// Compute normal impulse
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float vn = b2Dot(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 = b2Max(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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b2Vec2 P = lambda * normal;
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vA -= mA * P;
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wA -= iA * b2Cross(vcp->rA, P);
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vB += mB * P;
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wB += iB * b2Cross(vcp->rB, P);
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}
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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, 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
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// = A * x + b'
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// b' = b - A * a;
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b2VelocityConstraintPoint* cp1 = vc->points + 0;
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b2VelocityConstraintPoint* cp2 = vc->points + 1;
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b2Vec2 a(cp1->normalImpulse, cp2->normalImpulse);
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b2Assert(a.x >= 0.0f && a.y >= 0.0f);
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// Relative velocity at contact
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b2Vec2 dv1 = vB + b2Cross(wB, cp1->rB) - vA - b2Cross(wA, cp1->rA);
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b2Vec2 dv2 = vB + b2Cross(wB, cp2->rB) - vA - b2Cross(wA, cp2->rA);
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// Compute normal velocity
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float vn1 = b2Dot(dv1, normal);
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float vn2 = b2Dot(dv2, normal);
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b2Vec2 b;
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b.x = vn1 - cp1->velocityBias;
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b.y = vn2 - cp2->velocityBias;
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||||
|
||||
// Compute b'
|
||||
b -= b2Mul(vc->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'
|
||||
//
|
||||
b2Vec2 x = - b2Mul(vc->normalMass, b);
|
||||
|
||||
if (x.x >= 0.0f && x.y >= 0.0f)
|
||||
{
|
||||
// Get the incremental impulse
|
||||
b2Vec2 d = x - a;
|
||||
|
||||
// Apply incremental impulse
|
||||
b2Vec2 P1 = d.x * normal;
|
||||
b2Vec2 P2 = d.y * normal;
|
||||
vA -= mA * (P1 + P2);
|
||||
wA -= iA * (b2Cross(cp1->rA, P1) + b2Cross(cp2->rA, P2));
|
||||
|
||||
vB += mB * (P1 + P2);
|
||||
wB += iB * (b2Cross(cp1->rB, P1) + b2Cross(cp2->rB, P2));
|
||||
|
||||
// Accumulate
|
||||
cp1->normalImpulse = x.x;
|
||||
cp2->normalImpulse = x.y;
|
||||
|
||||
#if B2_DEBUG_SOLVER == 1
|
||||
// Postconditions
|
||||
dv1 = vB + b2Cross(wB, cp1->rB) - vA - b2Cross(wA, cp1->rA);
|
||||
dv2 = vB + b2Cross(wB, cp2->rB) - vA - b2Cross(wA, cp2->rA);
|
||||
|
||||
// Compute normal velocity
|
||||
vn1 = b2Dot(dv1, normal);
|
||||
vn2 = b2Dot(dv2, normal);
|
||||
|
||||
b2Assert(b2Abs(vn1 - cp1->velocityBias) < k_errorTol);
|
||||
b2Assert(b2Abs(vn2 - cp2->velocityBias) < k_errorTol);
|
||||
#endif
|
||||
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 = vc->K.ex.y * x.x + b.y;
|
||||
if (x.x >= 0.0f && vn2 >= 0.0f)
|
||||
{
|
||||
// Get the incremental impulse
|
||||
b2Vec2 d = x - a;
|
||||
|
||||
// Apply incremental impulse
|
||||
b2Vec2 P1 = d.x * normal;
|
||||
b2Vec2 P2 = d.y * normal;
|
||||
vA -= mA * (P1 + P2);
|
||||
wA -= iA * (b2Cross(cp1->rA, P1) + b2Cross(cp2->rA, P2));
|
||||
|
||||
vB += mB * (P1 + P2);
|
||||
wB += iB * (b2Cross(cp1->rB, P1) + b2Cross(cp2->rB, P2));
|
||||
|
||||
// Accumulate
|
||||
cp1->normalImpulse = x.x;
|
||||
cp2->normalImpulse = x.y;
|
||||
|
||||
#if B2_DEBUG_SOLVER == 1
|
||||
// Postconditions
|
||||
dv1 = vB + b2Cross(wB, cp1->rB) - vA - b2Cross(wA, cp1->rA);
|
||||
|
||||
// Compute normal velocity
|
||||
vn1 = b2Dot(dv1, normal);
|
||||
|
||||
b2Assert(b2Abs(vn1 - cp1->velocityBias) < k_errorTol);
|
||||
#endif
|
||||
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 = vc->K.ey.x * x.y + b.x;
|
||||
vn2 = 0.0f;
|
||||
|
||||
if (x.y >= 0.0f && vn1 >= 0.0f)
|
||||
{
|
||||
// Resubstitute for the incremental impulse
|
||||
b2Vec2 d = x - a;
|
||||
|
||||
// Apply incremental impulse
|
||||
b2Vec2 P1 = d.x * normal;
|
||||
b2Vec2 P2 = d.y * normal;
|
||||
vA -= mA * (P1 + P2);
|
||||
wA -= iA * (b2Cross(cp1->rA, P1) + b2Cross(cp2->rA, P2));
|
||||
|
||||
vB += mB * (P1 + P2);
|
||||
wB += iB * (b2Cross(cp1->rB, P1) + b2Cross(cp2->rB, P2));
|
||||
|
||||
// Accumulate
|
||||
cp1->normalImpulse = x.x;
|
||||
cp2->normalImpulse = x.y;
|
||||
|
||||
#if B2_DEBUG_SOLVER == 1
|
||||
// Postconditions
|
||||
dv2 = vB + b2Cross(wB, cp2->rB) - vA - b2Cross(wA, cp2->rA);
|
||||
|
||||
// Compute normal velocity
|
||||
vn2 = b2Dot(dv2, normal);
|
||||
|
||||
b2Assert(b2Abs(vn2 - cp2->velocityBias) < k_errorTol);
|
||||
#endif
|
||||
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
|
||||
b2Vec2 d = x - a;
|
||||
|
||||
// Apply incremental impulse
|
||||
b2Vec2 P1 = d.x * normal;
|
||||
b2Vec2 P2 = d.y * normal;
|
||||
vA -= mA * (P1 + P2);
|
||||
wA -= iA * (b2Cross(cp1->rA, P1) + b2Cross(cp2->rA, P2));
|
||||
|
||||
vB += mB * (P1 + P2);
|
||||
wB += iB * (b2Cross(cp1->rB, P1) + b2Cross(cp2->rB, 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;
|
||||
}
|
||||
}
|
||||
|
||||
m_velocities[indexA].v = vA;
|
||||
m_velocities[indexA].w = wA;
|
||||
m_velocities[indexB].v = vB;
|
||||
m_velocities[indexB].w = wB;
|
||||
}
|
||||
}
|
||||
|
||||
void b2ContactSolver::StoreImpulses()
|
||||
{
|
||||
for (int32 i = 0; i < m_count; ++i)
|
||||
{
|
||||
b2ContactVelocityConstraint* vc = m_velocityConstraints + i;
|
||||
b2Manifold* manifold = m_contacts[vc->contactIndex]->GetManifold();
|
||||
|
||||
for (int32 j = 0; j < vc->pointCount; ++j)
|
||||
{
|
||||
manifold->points[j].normalImpulse = vc->points[j].normalImpulse;
|
||||
manifold->points[j].tangentImpulse = vc->points[j].tangentImpulse;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
struct b2PositionSolverManifold
|
||||
{
|
||||
void Initialize(b2ContactPositionConstraint* pc, const b2Transform& xfA, const b2Transform& xfB, int32 index)
|
||||
{
|
||||
b2Assert(pc->pointCount > 0);
|
||||
|
||||
switch (pc->type)
|
||||
{
|
||||
case b2Manifold::e_circles:
|
||||
{
|
||||
b2Vec2 pointA = b2Mul(xfA, pc->localPoint);
|
||||
b2Vec2 pointB = b2Mul(xfB, pc->localPoints[0]);
|
||||
normal = pointB - pointA;
|
||||
normal.Normalize();
|
||||
point = 0.5f * (pointA + pointB);
|
||||
separation = b2Dot(pointB - pointA, normal) - pc->radiusA - pc->radiusB;
|
||||
}
|
||||
break;
|
||||
|
||||
case b2Manifold::e_faceA:
|
||||
{
|
||||
normal = b2Mul(xfA.q, pc->localNormal);
|
||||
b2Vec2 planePoint = b2Mul(xfA, pc->localPoint);
|
||||
|
||||
b2Vec2 clipPoint = b2Mul(xfB, pc->localPoints[index]);
|
||||
separation = b2Dot(clipPoint - planePoint, normal) - pc->radiusA - pc->radiusB;
|
||||
point = clipPoint;
|
||||
}
|
||||
break;
|
||||
|
||||
case b2Manifold::e_faceB:
|
||||
{
|
||||
normal = b2Mul(xfB.q, pc->localNormal);
|
||||
b2Vec2 planePoint = b2Mul(xfB, pc->localPoint);
|
||||
|
||||
b2Vec2 clipPoint = b2Mul(xfA, pc->localPoints[index]);
|
||||
separation = b2Dot(clipPoint - planePoint, normal) - pc->radiusA - pc->radiusB;
|
||||
point = clipPoint;
|
||||
|
||||
// Ensure normal points from A to B
|
||||
normal = -normal;
|
||||
}
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
b2Vec2 normal;
|
||||
b2Vec2 point;
|
||||
float separation;
|
||||
};
|
||||
|
||||
// Sequential solver.
|
||||
bool b2ContactSolver::SolvePositionConstraints()
|
||||
{
|
||||
float minSeparation = 0.0f;
|
||||
|
||||
for (int32 i = 0; i < m_count; ++i)
|
||||
{
|
||||
b2ContactPositionConstraint* pc = m_positionConstraints + i;
|
||||
|
||||
int32 indexA = pc->indexA;
|
||||
int32 indexB = pc->indexB;
|
||||
b2Vec2 localCenterA = pc->localCenterA;
|
||||
float mA = pc->invMassA;
|
||||
float iA = pc->invIA;
|
||||
b2Vec2 localCenterB = pc->localCenterB;
|
||||
float mB = pc->invMassB;
|
||||
float iB = pc->invIB;
|
||||
int32 pointCount = pc->pointCount;
|
||||
|
||||
b2Vec2 cA = m_positions[indexA].c;
|
||||
float aA = m_positions[indexA].a;
|
||||
|
||||
b2Vec2 cB = m_positions[indexB].c;
|
||||
float aB = m_positions[indexB].a;
|
||||
|
||||
// Solve normal constraints
|
||||
for (int32 j = 0; j < pointCount; ++j)
|
||||
{
|
||||
b2Transform xfA, xfB;
|
||||
xfA.q.Set(aA);
|
||||
xfB.q.Set(aB);
|
||||
xfA.p = cA - b2Mul(xfA.q, localCenterA);
|
||||
xfB.p = cB - b2Mul(xfB.q, localCenterB);
|
||||
|
||||
b2PositionSolverManifold psm;
|
||||
psm.Initialize(pc, xfA, xfB, j);
|
||||
b2Vec2 normal = psm.normal;
|
||||
|
||||
b2Vec2 point = psm.point;
|
||||
float separation = psm.separation;
|
||||
|
||||
b2Vec2 rA = point - cA;
|
||||
b2Vec2 rB = point - cB;
|
||||
|
||||
// Track max constraint error.
|
||||
minSeparation = b2Min(minSeparation, separation);
|
||||
|
||||
// Prevent large corrections and allow slop.
|
||||
float C = b2Clamp(b2_baumgarte * (separation + b2_linearSlop), -b2_maxLinearCorrection, 0.0f);
|
||||
|
||||
// Compute the effective mass.
|
||||
float rnA = b2Cross(rA, normal);
|
||||
float rnB = b2Cross(rB, normal);
|
||||
float K = mA + mB + iA * rnA * rnA + iB * rnB * rnB;
|
||||
|
||||
// Compute normal impulse
|
||||
float impulse = K > 0.0f ? - C / K : 0.0f;
|
||||
|
||||
b2Vec2 P = impulse * normal;
|
||||
|
||||
cA -= mA * P;
|
||||
aA -= iA * b2Cross(rA, P);
|
||||
|
||||
cB += mB * P;
|
||||
aB += iB * b2Cross(rB, P);
|
||||
}
|
||||
|
||||
m_positions[indexA].c = cA;
|
||||
m_positions[indexA].a = aA;
|
||||
|
||||
m_positions[indexB].c = cB;
|
||||
m_positions[indexB].a = aB;
|
||||
}
|
||||
|
||||
// We can't expect minSpeparation >= -b2_linearSlop because we don't
|
||||
// push the separation above -b2_linearSlop.
|
||||
return minSeparation >= -3.0f * b2_linearSlop;
|
||||
}
|
||||
|
||||
// Sequential position solver for position constraints.
|
||||
bool b2ContactSolver::SolveTOIPositionConstraints(int32 toiIndexA, int32 toiIndexB)
|
||||
{
|
||||
float minSeparation = 0.0f;
|
||||
|
||||
for (int32 i = 0; i < m_count; ++i)
|
||||
{
|
||||
b2ContactPositionConstraint* pc = m_positionConstraints + i;
|
||||
|
||||
int32 indexA = pc->indexA;
|
||||
int32 indexB = pc->indexB;
|
||||
b2Vec2 localCenterA = pc->localCenterA;
|
||||
b2Vec2 localCenterB = pc->localCenterB;
|
||||
int32 pointCount = pc->pointCount;
|
||||
|
||||
float mA = 0.0f;
|
||||
float iA = 0.0f;
|
||||
if (indexA == toiIndexA || indexA == toiIndexB)
|
||||
{
|
||||
mA = pc->invMassA;
|
||||
iA = pc->invIA;
|
||||
}
|
||||
|
||||
float mB = 0.0f;
|
||||
float iB = 0.;
|
||||
if (indexB == toiIndexA || indexB == toiIndexB)
|
||||
{
|
||||
mB = pc->invMassB;
|
||||
iB = pc->invIB;
|
||||
}
|
||||
|
||||
b2Vec2 cA = m_positions[indexA].c;
|
||||
float aA = m_positions[indexA].a;
|
||||
|
||||
b2Vec2 cB = m_positions[indexB].c;
|
||||
float aB = m_positions[indexB].a;
|
||||
|
||||
// Solve normal constraints
|
||||
for (int32 j = 0; j < pointCount; ++j)
|
||||
{
|
||||
b2Transform xfA, xfB;
|
||||
xfA.q.Set(aA);
|
||||
xfB.q.Set(aB);
|
||||
xfA.p = cA - b2Mul(xfA.q, localCenterA);
|
||||
xfB.p = cB - b2Mul(xfB.q, localCenterB);
|
||||
|
||||
b2PositionSolverManifold psm;
|
||||
psm.Initialize(pc, xfA, xfB, j);
|
||||
b2Vec2 normal = psm.normal;
|
||||
|
||||
b2Vec2 point = psm.point;
|
||||
float separation = psm.separation;
|
||||
|
||||
b2Vec2 rA = point - cA;
|
||||
b2Vec2 rB = point - cB;
|
||||
|
||||
// Track max constraint error.
|
||||
minSeparation = b2Min(minSeparation, separation);
|
||||
|
||||
// Prevent large corrections and allow slop.
|
||||
float C = b2Clamp(b2_toiBaumgarte * (separation + b2_linearSlop), -b2_maxLinearCorrection, 0.0f);
|
||||
|
||||
// Compute the effective mass.
|
||||
float rnA = b2Cross(rA, normal);
|
||||
float rnB = b2Cross(rB, normal);
|
||||
float K = mA + mB + iA * rnA * rnA + iB * rnB * rnB;
|
||||
|
||||
// Compute normal impulse
|
||||
float impulse = K > 0.0f ? - C / K : 0.0f;
|
||||
|
||||
b2Vec2 P = impulse * normal;
|
||||
|
||||
cA -= mA * P;
|
||||
aA -= iA * b2Cross(rA, P);
|
||||
|
||||
cB += mB * P;
|
||||
aB += iB * b2Cross(rB, P);
|
||||
}
|
||||
|
||||
m_positions[indexA].c = cA;
|
||||
m_positions[indexA].a = aA;
|
||||
|
||||
m_positions[indexB].c = cB;
|
||||
m_positions[indexB].a = aB;
|
||||
}
|
||||
|
||||
// We can't expect minSpeparation >= -b2_linearSlop because we don't
|
||||
// push the separation above -b2_linearSlop.
|
||||
return minSeparation >= -1.5f * b2_linearSlop;
|
||||
}
|
||||
Reference in New Issue
Block a user