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Diffstat (limited to 'src/3rdparty/Box2D/Dynamics/Joints/b2PulleyJoint.cpp')
| -rw-r--r-- | src/3rdparty/Box2D/Dynamics/Joints/b2PulleyJoint.cpp | 348 |
1 files changed, 348 insertions, 0 deletions
diff --git a/src/3rdparty/Box2D/Dynamics/Joints/b2PulleyJoint.cpp b/src/3rdparty/Box2D/Dynamics/Joints/b2PulleyJoint.cpp new file mode 100644 index 0000000..1525f41 --- /dev/null +++ b/src/3rdparty/Box2D/Dynamics/Joints/b2PulleyJoint.cpp @@ -0,0 +1,348 @@ +/* +* Copyright (c) 2007 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/b2PulleyJoint.h" +#include "Box2D/Dynamics/b2Body.h" +#include "Box2D/Dynamics/b2TimeStep.h" + +// Pulley: +// length1 = norm(p1 - s1) +// length2 = norm(p2 - s2) +// C0 = (length1 + ratio * length2)_initial +// C = C0 - (length1 + ratio * length2) +// u1 = (p1 - s1) / norm(p1 - s1) +// u2 = (p2 - s2) / norm(p2 - s2) +// Cdot = -dot(u1, v1 + cross(w1, r1)) - ratio * dot(u2, v2 + cross(w2, r2)) +// J = -[u1 cross(r1, u1) ratio * u2 ratio * cross(r2, u2)] +// K = J * invM * JT +// = invMass1 + invI1 * cross(r1, u1)^2 + ratio^2 * (invMass2 + invI2 * cross(r2, u2)^2) + +void b2PulleyJointDef::Initialize(b2Body* bA, b2Body* bB, + const b2Vec2& groundA, const b2Vec2& groundB, + const b2Vec2& anchorA, const b2Vec2& anchorB, + float32 r) +{ + bodyA = bA; + bodyB = bB; + groundAnchorA = groundA; + groundAnchorB = groundB; + localAnchorA = bodyA->GetLocalPoint(anchorA); + localAnchorB = bodyB->GetLocalPoint(anchorB); + b2Vec2 dA = anchorA - groundA; + lengthA = dA.Length(); + b2Vec2 dB = anchorB - groundB; + lengthB = dB.Length(); + ratio = r; + b2Assert(ratio > b2_epsilon); +} + +b2PulleyJoint::b2PulleyJoint(const b2PulleyJointDef* def) +: b2Joint(def) +{ + m_groundAnchorA = def->groundAnchorA; + m_groundAnchorB = def->groundAnchorB; + m_localAnchorA = def->localAnchorA; + m_localAnchorB = def->localAnchorB; + + m_lengthA = def->lengthA; + m_lengthB = def->lengthB; + + b2Assert(def->ratio != 0.0f); + m_ratio = def->ratio; + + m_constant = def->lengthA + m_ratio * def->lengthB; + + m_impulse = 0.0f; +} + +void b2PulleyJoint::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); + + // Get the pulley axes. + m_uA = cA + m_rA - m_groundAnchorA; + m_uB = cB + m_rB - m_groundAnchorB; + + float32 lengthA = m_uA.Length(); + float32 lengthB = m_uB.Length(); + + if (lengthA > 10.0f * b2_linearSlop) + { + m_uA *= 1.0f / lengthA; + } + else + { + m_uA.SetZero(); + } + + if (lengthB > 10.0f * b2_linearSlop) + { + m_uB *= 1.0f / lengthB; + } + else + { + m_uB.SetZero(); + } + + // Compute effective mass. + float32 ruA = b2Cross(m_rA, m_uA); + float32 ruB = b2Cross(m_rB, m_uB); + + float32 mA = m_invMassA + m_invIA * ruA * ruA; + float32 mB = m_invMassB + m_invIB * ruB * ruB; + + m_mass = mA + m_ratio * m_ratio * mB; + + if (m_mass > 0.0f) + { + m_mass = 1.0f / m_mass; + } + + if (data.step.warmStarting) + { + // Scale impulses to support variable time steps. + m_impulse *= data.step.dtRatio; + + // Warm starting. + b2Vec2 PA = -(m_impulse) * m_uA; + b2Vec2 PB = (-m_ratio * m_impulse) * m_uB; + + vA += m_invMassA * PA; + wA += m_invIA * b2Cross(m_rA, PA); + vB += m_invMassB * PB; + wB += m_invIB * b2Cross(m_rB, PB); + } + 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 b2PulleyJoint::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; + + b2Vec2 vpA = vA + b2Cross(wA, m_rA); + b2Vec2 vpB = vB + b2Cross(wB, m_rB); + + float32 Cdot = -b2Dot(m_uA, vpA) - m_ratio * b2Dot(m_uB, vpB); + float32 impulse = -m_mass * Cdot; + m_impulse += impulse; + + b2Vec2 PA = -impulse * m_uA; + b2Vec2 PB = -m_ratio * impulse * m_uB; + vA += m_invMassA * PA; + wA += m_invIA * b2Cross(m_rA, PA); + vB += m_invMassB * PB; + wB += m_invIB * b2Cross(m_rB, PB); + + 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 b2PulleyJoint::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); + + // Get the pulley axes. + b2Vec2 uA = cA + rA - m_groundAnchorA; + b2Vec2 uB = cB + rB - m_groundAnchorB; + + float32 lengthA = uA.Length(); + float32 lengthB = uB.Length(); + + if (lengthA > 10.0f * b2_linearSlop) + { + uA *= 1.0f / lengthA; + } + else + { + uA.SetZero(); + } + + if (lengthB > 10.0f * b2_linearSlop) + { + uB *= 1.0f / lengthB; + } + else + { + uB.SetZero(); + } + + // Compute effective mass. + float32 ruA = b2Cross(rA, uA); + float32 ruB = b2Cross(rB, uB); + + float32 mA = m_invMassA + m_invIA * ruA * ruA; + float32 mB = m_invMassB + m_invIB * ruB * ruB; + + float32 mass = mA + m_ratio * m_ratio * mB; + + if (mass > 0.0f) + { + mass = 1.0f / mass; + } + + float32 C = m_constant - lengthA - m_ratio * lengthB; + float32 linearError = b2Abs(C); + + float32 impulse = -mass * C; + + b2Vec2 PA = -impulse * uA; + b2Vec2 PB = -m_ratio * impulse * uB; + + cA += m_invMassA * PA; + aA += m_invIA * b2Cross(rA, PA); + cB += m_invMassB * PB; + aB += m_invIB * b2Cross(rB, PB); + + 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 linearError < b2_linearSlop; +} + +b2Vec2 b2PulleyJoint::GetAnchorA() const +{ + return m_bodyA->GetWorldPoint(m_localAnchorA); +} + +b2Vec2 b2PulleyJoint::GetAnchorB() const +{ + return m_bodyB->GetWorldPoint(m_localAnchorB); +} + +b2Vec2 b2PulleyJoint::GetReactionForce(float32 inv_dt) const +{ + b2Vec2 P = m_impulse * m_uB; + return inv_dt * P; +} + +float32 b2PulleyJoint::GetReactionTorque(float32 inv_dt) const +{ + B2_NOT_USED(inv_dt); + return 0.0f; +} + +b2Vec2 b2PulleyJoint::GetGroundAnchorA() const +{ + return m_groundAnchorA; +} + +b2Vec2 b2PulleyJoint::GetGroundAnchorB() const +{ + return m_groundAnchorB; +} + +float32 b2PulleyJoint::GetLengthA() const +{ + return m_lengthA; +} + +float32 b2PulleyJoint::GetLengthB() const +{ + return m_lengthB; +} + +float32 b2PulleyJoint::GetRatio() const +{ + return m_ratio; +} + +float32 b2PulleyJoint::GetCurrentLengthA() const +{ + b2Vec2 p = m_bodyA->GetWorldPoint(m_localAnchorA); + b2Vec2 s = m_groundAnchorA; + b2Vec2 d = p - s; + return d.Length(); +} + +float32 b2PulleyJoint::GetCurrentLengthB() const +{ + b2Vec2 p = m_bodyB->GetWorldPoint(m_localAnchorB); + b2Vec2 s = m_groundAnchorB; + b2Vec2 d = p - s; + return d.Length(); +} + +void b2PulleyJoint::Dump() +{ + int32 indexA = m_bodyA->m_islandIndex; + int32 indexB = m_bodyB->m_islandIndex; + + b2Log(" b2PulleyJointDef 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.groundAnchorA.Set(%.15lef, %.15lef);\n", m_groundAnchorA.x, m_groundAnchorA.y); + b2Log(" jd.groundAnchorB.Set(%.15lef, %.15lef);\n", m_groundAnchorB.x, m_groundAnchorB.y); + 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.lengthA = %.15lef;\n", m_lengthA); + b2Log(" jd.lengthB = %.15lef;\n", m_lengthB); + b2Log(" jd.ratio = %.15lef;\n", m_ratio); + b2Log(" joints[%d] = m_world->CreateJoint(&jd);\n", m_index); +} + +void b2PulleyJoint::ShiftOrigin(const b2Vec2& newOrigin) +{ + m_groundAnchorA -= newOrigin; + m_groundAnchorB -= newOrigin; +} |