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authorchai <chaifix@163.com>2019-03-19 23:06:27 +0800
committerchai <chaifix@163.com>2019-03-19 23:06:27 +0800
commit1497dccd63a84b7ee2b229b1ad9c5c02718f2a78 (patch)
treef8d1bff50da13e126d08c7345653e002e293202d /Source/3rdParty/Box2D/Dynamics/Joints/b2DistanceJoint.cpp
parent5e2a973516e0729b225da9de0b03015dc5854ac4 (diff)
*rename
Diffstat (limited to 'Source/3rdParty/Box2D/Dynamics/Joints/b2DistanceJoint.cpp')
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diff --git a/Source/3rdParty/Box2D/Dynamics/Joints/b2DistanceJoint.cpp b/Source/3rdParty/Box2D/Dynamics/Joints/b2DistanceJoint.cpp
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-/*
-* Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
-*
-* This software is provided 'as-is', without any express or implied
-* warranty. In no event will the authors be held liable for any damages
-* arising from the use of this software.
-* Permission is granted to anyone to use this software for any purpose,
-* including commercial applications, and to alter it and redistribute it
-* freely, subject to the following restrictions:
-* 1. The origin of this software must not be misrepresented; you must not
-* claim that you wrote the original software. If you use this software
-* in a product, an acknowledgment in the product documentation would be
-* appreciated but is not required.
-* 2. Altered source versions must be plainly marked as such, and must not be
-* misrepresented as being the original software.
-* 3. This notice may not be removed or altered from any source distribution.
-*/
-
-#include "Box2D/Dynamics/Joints/b2DistanceJoint.h"
-#include "Box2D/Dynamics/b2Body.h"
-#include "Box2D/Dynamics/b2TimeStep.h"
-
-// 1-D constrained system
-// m (v2 - v1) = lambda
-// v2 + (beta/h) * x1 + gamma * lambda = 0, gamma has units of inverse mass.
-// x2 = x1 + h * v2
-
-// 1-D mass-damper-spring system
-// m (v2 - v1) + h * d * v2 + h * k *
-
-// C = norm(p2 - p1) - L
-// u = (p2 - p1) / norm(p2 - p1)
-// Cdot = dot(u, v2 + cross(w2, r2) - v1 - cross(w1, r1))
-// J = [-u -cross(r1, u) u cross(r2, u)]
-// K = J * invM * JT
-// = invMass1 + invI1 * cross(r1, u)^2 + invMass2 + invI2 * cross(r2, u)^2
-
-void b2DistanceJointDef::Initialize(b2Body* b1, b2Body* b2,
- const b2Vec2& anchor1, const b2Vec2& anchor2)
-{
- bodyA = b1;
- bodyB = b2;
- localAnchorA = bodyA->GetLocalPoint(anchor1);
- localAnchorB = bodyB->GetLocalPoint(anchor2);
- b2Vec2 d = anchor2 - anchor1;
- length = d.Length();
-}
-
-b2DistanceJoint::b2DistanceJoint(const b2DistanceJointDef* def)
-: b2Joint(def)
-{
- m_localAnchorA = def->localAnchorA;
- m_localAnchorB = def->localAnchorB;
- m_length = def->length;
- m_frequencyHz = def->frequencyHz;
- m_dampingRatio = def->dampingRatio;
- m_impulse = 0.0f;
- m_gamma = 0.0f;
- m_bias = 0.0f;
-}
-
-void b2DistanceJoint::InitVelocityConstraints(const b2SolverData& data)
-{
- m_indexA = m_bodyA->m_islandIndex;
- m_indexB = m_bodyB->m_islandIndex;
- m_localCenterA = m_bodyA->m_sweep.localCenter;
- m_localCenterB = m_bodyB->m_sweep.localCenter;
- m_invMassA = m_bodyA->m_invMass;
- m_invMassB = m_bodyB->m_invMass;
- m_invIA = m_bodyA->m_invI;
- m_invIB = m_bodyB->m_invI;
-
- b2Vec2 cA = data.positions[m_indexA].c;
- float32 aA = data.positions[m_indexA].a;
- b2Vec2 vA = data.velocities[m_indexA].v;
- float32 wA = data.velocities[m_indexA].w;
-
- b2Vec2 cB = data.positions[m_indexB].c;
- float32 aB = data.positions[m_indexB].a;
- b2Vec2 vB = data.velocities[m_indexB].v;
- float32 wB = data.velocities[m_indexB].w;
-
- b2Rot qA(aA), qB(aB);
-
- m_rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
- m_rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
- m_u = cB + m_rB - cA - m_rA;
-
- // Handle singularity.
- float32 length = m_u.Length();
- if (length > b2_linearSlop)
- {
- m_u *= 1.0f / length;
- }
- else
- {
- m_u.Set(0.0f, 0.0f);
- }
-
- float32 crAu = b2Cross(m_rA, m_u);
- float32 crBu = b2Cross(m_rB, m_u);
- float32 invMass = m_invMassA + m_invIA * crAu * crAu + m_invMassB + m_invIB * crBu * crBu;
-
- // Compute the effective mass matrix.
- m_mass = invMass != 0.0f ? 1.0f / invMass : 0.0f;
-
- if (m_frequencyHz > 0.0f)
- {
- float32 C = length - m_length;
-
- // Frequency
- float32 omega = 2.0f * b2_pi * m_frequencyHz;
-
- // Damping coefficient
- float32 d = 2.0f * m_mass * m_dampingRatio * omega;
-
- // Spring stiffness
- float32 k = m_mass * omega * omega;
-
- // magic formulas
- float32 h = data.step.dt;
- m_gamma = h * (d + h * k);
- m_gamma = m_gamma != 0.0f ? 1.0f / m_gamma : 0.0f;
- m_bias = C * h * k * m_gamma;
-
- invMass += m_gamma;
- m_mass = invMass != 0.0f ? 1.0f / invMass : 0.0f;
- }
- else
- {
- m_gamma = 0.0f;
- m_bias = 0.0f;
- }
-
- if (data.step.warmStarting)
- {
- // Scale the impulse to support a variable time step.
- m_impulse *= data.step.dtRatio;
-
- b2Vec2 P = m_impulse * m_u;
- vA -= m_invMassA * P;
- wA -= m_invIA * b2Cross(m_rA, P);
- vB += m_invMassB * P;
- wB += m_invIB * b2Cross(m_rB, P);
- }
- else
- {
- m_impulse = 0.0f;
- }
-
- data.velocities[m_indexA].v = vA;
- data.velocities[m_indexA].w = wA;
- data.velocities[m_indexB].v = vB;
- data.velocities[m_indexB].w = wB;
-}
-
-void b2DistanceJoint::SolveVelocityConstraints(const b2SolverData& data)
-{
- b2Vec2 vA = data.velocities[m_indexA].v;
- float32 wA = data.velocities[m_indexA].w;
- b2Vec2 vB = data.velocities[m_indexB].v;
- float32 wB = data.velocities[m_indexB].w;
-
- // Cdot = dot(u, v + cross(w, r))
- b2Vec2 vpA = vA + b2Cross(wA, m_rA);
- b2Vec2 vpB = vB + b2Cross(wB, m_rB);
- float32 Cdot = b2Dot(m_u, vpB - vpA);
-
- float32 impulse = -m_mass * (Cdot + m_bias + m_gamma * m_impulse);
- m_impulse += impulse;
-
- b2Vec2 P = impulse * m_u;
- vA -= m_invMassA * P;
- wA -= m_invIA * b2Cross(m_rA, P);
- vB += m_invMassB * P;
- wB += m_invIB * b2Cross(m_rB, P);
-
- data.velocities[m_indexA].v = vA;
- data.velocities[m_indexA].w = wA;
- data.velocities[m_indexB].v = vB;
- data.velocities[m_indexB].w = wB;
-}
-
-bool b2DistanceJoint::SolvePositionConstraints(const b2SolverData& data)
-{
- if (m_frequencyHz > 0.0f)
- {
- // There is no position correction for soft distance constraints.
- return true;
- }
-
- b2Vec2 cA = data.positions[m_indexA].c;
- float32 aA = data.positions[m_indexA].a;
- b2Vec2 cB = data.positions[m_indexB].c;
- float32 aB = data.positions[m_indexB].a;
-
- b2Rot qA(aA), qB(aB);
-
- b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
- b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
- b2Vec2 u = cB + rB - cA - rA;
-
- float32 length = u.Normalize();
- float32 C = length - m_length;
- C = b2Clamp(C, -b2_maxLinearCorrection, b2_maxLinearCorrection);
-
- float32 impulse = -m_mass * C;
- b2Vec2 P = impulse * u;
-
- cA -= m_invMassA * P;
- aA -= m_invIA * b2Cross(rA, P);
- cB += m_invMassB * P;
- aB += m_invIB * b2Cross(rB, P);
-
- data.positions[m_indexA].c = cA;
- data.positions[m_indexA].a = aA;
- data.positions[m_indexB].c = cB;
- data.positions[m_indexB].a = aB;
-
- return b2Abs(C) < b2_linearSlop;
-}
-
-b2Vec2 b2DistanceJoint::GetAnchorA() const
-{
- return m_bodyA->GetWorldPoint(m_localAnchorA);
-}
-
-b2Vec2 b2DistanceJoint::GetAnchorB() const
-{
- return m_bodyB->GetWorldPoint(m_localAnchorB);
-}
-
-b2Vec2 b2DistanceJoint::GetReactionForce(float32 inv_dt) const
-{
- b2Vec2 F = (inv_dt * m_impulse) * m_u;
- return F;
-}
-
-float32 b2DistanceJoint::GetReactionTorque(float32 inv_dt) const
-{
- B2_NOT_USED(inv_dt);
- return 0.0f;
-}
-
-void b2DistanceJoint::Dump()
-{
- int32 indexA = m_bodyA->m_islandIndex;
- int32 indexB = m_bodyB->m_islandIndex;
-
- b2Log(" b2DistanceJointDef jd;\n");
- b2Log(" jd.bodyA = bodies[%d];\n", indexA);
- b2Log(" jd.bodyB = bodies[%d];\n", indexB);
- b2Log(" jd.collideConnected = bool(%d);\n", m_collideConnected);
- b2Log(" jd.localAnchorA.Set(%.15lef, %.15lef);\n", m_localAnchorA.x, m_localAnchorA.y);
- b2Log(" jd.localAnchorB.Set(%.15lef, %.15lef);\n", m_localAnchorB.x, m_localAnchorB.y);
- b2Log(" jd.length = %.15lef;\n", m_length);
- b2Log(" jd.frequencyHz = %.15lef;\n", m_frequencyHz);
- b2Log(" jd.dampingRatio = %.15lef;\n", m_dampingRatio);
- b2Log(" joints[%d] = m_world->CreateJoint(&jd);\n", m_index);
-}