diff options
Diffstat (limited to 'src/3rdparty/Box2D/Dynamics/Joints/b2WheelJoint.cpp')
-rw-r--r-- | src/3rdparty/Box2D/Dynamics/Joints/b2WheelJoint.cpp | 456 |
1 files changed, 456 insertions, 0 deletions
diff --git a/src/3rdparty/Box2D/Dynamics/Joints/b2WheelJoint.cpp b/src/3rdparty/Box2D/Dynamics/Joints/b2WheelJoint.cpp new file mode 100644 index 0000000..a95311e --- /dev/null +++ b/src/3rdparty/Box2D/Dynamics/Joints/b2WheelJoint.cpp @@ -0,0 +1,456 @@ +/* +* Copyright (c) 2006-2007 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/b2WheelJoint.h" +#include "Box2D/Dynamics/b2Body.h" +#include "Box2D/Dynamics/b2TimeStep.h" + +// Linear constraint (point-to-line) +// d = pB - pA = xB + rB - xA - rA +// C = dot(ay, d) +// Cdot = dot(d, cross(wA, ay)) + dot(ay, vB + cross(wB, rB) - vA - cross(wA, rA)) +// = -dot(ay, vA) - dot(cross(d + rA, ay), wA) + dot(ay, vB) + dot(cross(rB, ay), vB) +// J = [-ay, -cross(d + rA, ay), ay, cross(rB, ay)] + +// Spring linear constraint +// C = dot(ax, d) +// Cdot = = -dot(ax, vA) - dot(cross(d + rA, ax), wA) + dot(ax, vB) + dot(cross(rB, ax), vB) +// J = [-ax -cross(d+rA, ax) ax cross(rB, ax)] + +// Motor rotational constraint +// Cdot = wB - wA +// J = [0 0 -1 0 0 1] + +void b2WheelJointDef::Initialize(b2Body* bA, b2Body* bB, const b2Vec2& anchor, const b2Vec2& axis) +{ + bodyA = bA; + bodyB = bB; + localAnchorA = bodyA->GetLocalPoint(anchor); + localAnchorB = bodyB->GetLocalPoint(anchor); + localAxisA = bodyA->GetLocalVector(axis); +} + +b2WheelJoint::b2WheelJoint(const b2WheelJointDef* def) +: b2Joint(def) +{ + m_localAnchorA = def->localAnchorA; + m_localAnchorB = def->localAnchorB; + m_localXAxisA = def->localAxisA; + m_localYAxisA = b2Cross(1.0f, m_localXAxisA); + + m_mass = 0.0f; + m_impulse = 0.0f; + m_motorMass = 0.0f; + m_motorImpulse = 0.0f; + m_springMass = 0.0f; + m_springImpulse = 0.0f; + + m_maxMotorTorque = def->maxMotorTorque; + m_motorSpeed = def->motorSpeed; + m_enableMotor = def->enableMotor; + + m_frequencyHz = def->frequencyHz; + m_dampingRatio = def->dampingRatio; + + m_bias = 0.0f; + m_gamma = 0.0f; + + m_ax.SetZero(); + m_ay.SetZero(); +} + +void b2WheelJoint::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; + + float32 mA = m_invMassA, mB = m_invMassB; + float32 iA = m_invIA, iB = m_invIB; + + 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); + + // Compute the effective masses. + b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_localCenterA); + b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_localCenterB); + b2Vec2 d = cB + rB - cA - rA; + + // Point to line constraint + { + m_ay = b2Mul(qA, m_localYAxisA); + m_sAy = b2Cross(d + rA, m_ay); + m_sBy = b2Cross(rB, m_ay); + + m_mass = mA + mB + iA * m_sAy * m_sAy + iB * m_sBy * m_sBy; + + if (m_mass > 0.0f) + { + m_mass = 1.0f / m_mass; + } + } + + // Spring constraint + m_springMass = 0.0f; + m_bias = 0.0f; + m_gamma = 0.0f; + if (m_frequencyHz > 0.0f) + { + m_ax = b2Mul(qA, m_localXAxisA); + m_sAx = b2Cross(d + rA, m_ax); + m_sBx = b2Cross(rB, m_ax); + + float32 invMass = mA + mB + iA * m_sAx * m_sAx + iB * m_sBx * m_sBx; + + if (invMass > 0.0f) + { + m_springMass = 1.0f / invMass; + + float32 C = b2Dot(d, m_ax); + + // Frequency + float32 omega = 2.0f * b2_pi * m_frequencyHz; + + // Damping coefficient + float32 damp = 2.0f * m_springMass * m_dampingRatio * omega; + + // Spring stiffness + float32 k = m_springMass * omega * omega; + + // magic formulas + float32 h = data.step.dt; + m_gamma = h * (damp + h * k); + if (m_gamma > 0.0f) + { + m_gamma = 1.0f / m_gamma; + } + + m_bias = C * h * k * m_gamma; + + m_springMass = invMass + m_gamma; + if (m_springMass > 0.0f) + { + m_springMass = 1.0f / m_springMass; + } + } + } + else + { + m_springImpulse = 0.0f; + } + + // Rotational motor + if (m_enableMotor) + { + m_motorMass = iA + iB; + if (m_motorMass > 0.0f) + { + m_motorMass = 1.0f / m_motorMass; + } + } + else + { + m_motorMass = 0.0f; + m_motorImpulse = 0.0f; + } + + if (data.step.warmStarting) + { + // Account for variable time step. + m_impulse *= data.step.dtRatio; + m_springImpulse *= data.step.dtRatio; + m_motorImpulse *= data.step.dtRatio; + + b2Vec2 P = m_impulse * m_ay + m_springImpulse * m_ax; + float32 LA = m_impulse * m_sAy + m_springImpulse * m_sAx + m_motorImpulse; + float32 LB = m_impulse * m_sBy + m_springImpulse * m_sBx + m_motorImpulse; + + vA -= m_invMassA * P; + wA -= m_invIA * LA; + + vB += m_invMassB * P; + wB += m_invIB * LB; + } + else + { + m_impulse = 0.0f; + m_springImpulse = 0.0f; + m_motorImpulse = 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 b2WheelJoint::SolveVelocityConstraints(const b2SolverData& data) +{ + float32 mA = m_invMassA, mB = m_invMassB; + float32 iA = m_invIA, iB = m_invIB; + + 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; + + // Solve spring constraint + { + float32 Cdot = b2Dot(m_ax, vB - vA) + m_sBx * wB - m_sAx * wA; + float32 impulse = -m_springMass * (Cdot + m_bias + m_gamma * m_springImpulse); + m_springImpulse += impulse; + + b2Vec2 P = impulse * m_ax; + float32 LA = impulse * m_sAx; + float32 LB = impulse * m_sBx; + + vA -= mA * P; + wA -= iA * LA; + + vB += mB * P; + wB += iB * LB; + } + + // Solve rotational motor constraint + { + float32 Cdot = wB - wA - m_motorSpeed; + float32 impulse = -m_motorMass * Cdot; + + float32 oldImpulse = m_motorImpulse; + float32 maxImpulse = data.step.dt * m_maxMotorTorque; + m_motorImpulse = b2Clamp(m_motorImpulse + impulse, -maxImpulse, maxImpulse); + impulse = m_motorImpulse - oldImpulse; + + wA -= iA * impulse; + wB += iB * impulse; + } + + // Solve point to line constraint + { + float32 Cdot = b2Dot(m_ay, vB - vA) + m_sBy * wB - m_sAy * wA; + float32 impulse = -m_mass * Cdot; + m_impulse += impulse; + + b2Vec2 P = impulse * m_ay; + float32 LA = impulse * m_sAy; + float32 LB = impulse * m_sBy; + + vA -= mA * P; + wA -= iA * LA; + + vB += mB * P; + wB += iB * LB; + } + + 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 b2WheelJoint::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 d = (cB - cA) + rB - rA; + + b2Vec2 ay = b2Mul(qA, m_localYAxisA); + + float32 sAy = b2Cross(d + rA, ay); + float32 sBy = b2Cross(rB, ay); + + float32 C = b2Dot(d, ay); + + float32 k = m_invMassA + m_invMassB + m_invIA * m_sAy * m_sAy + m_invIB * m_sBy * m_sBy; + + float32 impulse; + if (k != 0.0f) + { + impulse = - C / k; + } + else + { + impulse = 0.0f; + } + + b2Vec2 P = impulse * ay; + float32 LA = impulse * sAy; + float32 LB = impulse * sBy; + + cA -= m_invMassA * P; + aA -= m_invIA * LA; + cB += m_invMassB * P; + aB += m_invIB * LB; + + 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 b2WheelJoint::GetAnchorA() const +{ + return m_bodyA->GetWorldPoint(m_localAnchorA); +} + +b2Vec2 b2WheelJoint::GetAnchorB() const +{ + return m_bodyB->GetWorldPoint(m_localAnchorB); +} + +b2Vec2 b2WheelJoint::GetReactionForce(float32 inv_dt) const +{ + return inv_dt * (m_impulse * m_ay + m_springImpulse * m_ax); +} + +float32 b2WheelJoint::GetReactionTorque(float32 inv_dt) const +{ + return inv_dt * m_motorImpulse; +} + +float32 b2WheelJoint::GetJointTranslation() const +{ + b2Body* bA = m_bodyA; + b2Body* bB = m_bodyB; + + b2Vec2 pA = bA->GetWorldPoint(m_localAnchorA); + b2Vec2 pB = bB->GetWorldPoint(m_localAnchorB); + b2Vec2 d = pB - pA; + b2Vec2 axis = bA->GetWorldVector(m_localXAxisA); + + float32 translation = b2Dot(d, axis); + return translation; +} + +float32 b2WheelJoint::GetJointLinearSpeed() const +{ + b2Body* bA = m_bodyA; + b2Body* bB = m_bodyB; + + b2Vec2 rA = b2Mul(bA->m_xf.q, m_localAnchorA - bA->m_sweep.localCenter); + b2Vec2 rB = b2Mul(bB->m_xf.q, m_localAnchorB - bB->m_sweep.localCenter); + b2Vec2 p1 = bA->m_sweep.c + rA; + b2Vec2 p2 = bB->m_sweep.c + rB; + b2Vec2 d = p2 - p1; + b2Vec2 axis = b2Mul(bA->m_xf.q, m_localXAxisA); + + b2Vec2 vA = bA->m_linearVelocity; + b2Vec2 vB = bB->m_linearVelocity; + float32 wA = bA->m_angularVelocity; + float32 wB = bB->m_angularVelocity; + + float32 speed = b2Dot(d, b2Cross(wA, axis)) + b2Dot(axis, vB + b2Cross(wB, rB) - vA - b2Cross(wA, rA)); + return speed; +} + +float32 b2WheelJoint::GetJointAngle() const +{ + b2Body* bA = m_bodyA; + b2Body* bB = m_bodyB; + return bB->m_sweep.a - bA->m_sweep.a; +} + +float32 b2WheelJoint::GetJointAngularSpeed() const +{ + float32 wA = m_bodyA->m_angularVelocity; + float32 wB = m_bodyB->m_angularVelocity; + return wB - wA; +} + +bool b2WheelJoint::IsMotorEnabled() const +{ + return m_enableMotor; +} + +void b2WheelJoint::EnableMotor(bool flag) +{ + if (flag != m_enableMotor) + { + m_bodyA->SetAwake(true); + m_bodyB->SetAwake(true); + m_enableMotor = flag; + } +} + +void b2WheelJoint::SetMotorSpeed(float32 speed) +{ + if (speed != m_motorSpeed) + { + m_bodyA->SetAwake(true); + m_bodyB->SetAwake(true); + m_motorSpeed = speed; + } +} + +void b2WheelJoint::SetMaxMotorTorque(float32 torque) +{ + if (torque != m_maxMotorTorque) + { + m_bodyA->SetAwake(true); + m_bodyB->SetAwake(true); + m_maxMotorTorque = torque; + } +} + +float32 b2WheelJoint::GetMotorTorque(float32 inv_dt) const +{ + return inv_dt * m_motorImpulse; +} + +void b2WheelJoint::Dump() +{ + int32 indexA = m_bodyA->m_islandIndex; + int32 indexB = m_bodyB->m_islandIndex; + + b2Log(" b2WheelJointDef 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.localAxisA.Set(%.15lef, %.15lef);\n", m_localXAxisA.x, m_localXAxisA.y); + b2Log(" jd.enableMotor = bool(%d);\n", m_enableMotor); + b2Log(" jd.motorSpeed = %.15lef;\n", m_motorSpeed); + b2Log(" jd.maxMotorTorque = %.15lef;\n", m_maxMotorTorque); + b2Log(" jd.frequencyHz = %.15lef;\n", m_frequencyHz); + b2Log(" jd.dampingRatio = %.15lef;\n", m_dampingRatio); + b2Log(" joints[%d] = m_world->CreateJoint(&jd);\n", m_index); +} |