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Diffstat (limited to 'src/3rdparty/Box2D/Dynamics/Joints/b2RopeJoint.cpp')
| -rw-r--r-- | src/3rdparty/Box2D/Dynamics/Joints/b2RopeJoint.cpp | 241 |
1 files changed, 241 insertions, 0 deletions
diff --git a/src/3rdparty/Box2D/Dynamics/Joints/b2RopeJoint.cpp b/src/3rdparty/Box2D/Dynamics/Joints/b2RopeJoint.cpp new file mode 100644 index 0000000..86d27e7 --- /dev/null +++ b/src/3rdparty/Box2D/Dynamics/Joints/b2RopeJoint.cpp @@ -0,0 +1,241 @@ +/* +* Copyright (c) 2007-2011 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/b2RopeJoint.h" +#include "Box2D/Dynamics/b2Body.h" +#include "Box2D/Dynamics/b2TimeStep.h" + + +// Limit: +// C = norm(pB - pA) - L +// u = (pB - pA) / norm(pB - pA) +// Cdot = dot(u, vB + cross(wB, rB) - vA - cross(wA, rA)) +// J = [-u -cross(rA, u) u cross(rB, u)] +// K = J * invM * JT +// = invMassA + invIA * cross(rA, u)^2 + invMassB + invIB * cross(rB, u)^2 + +b2RopeJoint::b2RopeJoint(const b2RopeJointDef* def) +: b2Joint(def) +{ + m_localAnchorA = def->localAnchorA; + m_localAnchorB = def->localAnchorB; + + m_maxLength = def->maxLength; + + m_mass = 0.0f; + m_impulse = 0.0f; + m_state = e_inactiveLimit; + m_length = 0.0f; +} + +void b2RopeJoint::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; + + m_length = m_u.Length(); + + float32 C = m_length - m_maxLength; + if (C > 0.0f) + { + m_state = e_atUpperLimit; + } + else + { + m_state = e_inactiveLimit; + } + + if (m_length > b2_linearSlop) + { + m_u *= 1.0f / m_length; + } + else + { + m_u.SetZero(); + m_mass = 0.0f; + m_impulse = 0.0f; + return; + } + + // Compute effective mass. + float32 crA = b2Cross(m_rA, m_u); + float32 crB = b2Cross(m_rB, m_u); + float32 invMass = m_invMassA + m_invIA * crA * crA + m_invMassB + m_invIB * crB * crB; + + m_mass = invMass != 0.0f ? 1.0f / invMass : 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 b2RopeJoint::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 C = m_length - m_maxLength; + float32 Cdot = b2Dot(m_u, vpB - vpA); + + // Predictive constraint. + if (C < 0.0f) + { + Cdot += data.step.inv_dt * C; + } + + float32 impulse = -m_mass * Cdot; + float32 oldImpulse = m_impulse; + m_impulse = b2Min(0.0f, m_impulse + impulse); + impulse = m_impulse - oldImpulse; + + 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 b2RopeJoint::SolvePositionConstraints(const b2SolverData& data) +{ + 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_maxLength; + + C = b2Clamp(C, 0.0f, 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 length - m_maxLength < b2_linearSlop; +} + +b2Vec2 b2RopeJoint::GetAnchorA() const +{ + return m_bodyA->GetWorldPoint(m_localAnchorA); +} + +b2Vec2 b2RopeJoint::GetAnchorB() const +{ + return m_bodyB->GetWorldPoint(m_localAnchorB); +} + +b2Vec2 b2RopeJoint::GetReactionForce(float32 inv_dt) const +{ + b2Vec2 F = (inv_dt * m_impulse) * m_u; + return F; +} + +float32 b2RopeJoint::GetReactionTorque(float32 inv_dt) const +{ + B2_NOT_USED(inv_dt); + return 0.0f; +} + +float32 b2RopeJoint::GetMaxLength() const +{ + return m_maxLength; +} + +b2LimitState b2RopeJoint::GetLimitState() const +{ + return m_state; +} + +void b2RopeJoint::Dump() +{ + int32 indexA = m_bodyA->m_islandIndex; + int32 indexB = m_bodyB->m_islandIndex; + + b2Log(" b2RopeJointDef 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.maxLength = %.15lef;\n", m_maxLength); + b2Log(" joints[%d] = m_world->CreateJoint(&jd);\n", m_index); +} |