X-Git-Url: https://vcs.maemo.org/git/?a=blobdiff_plain;f=Box2D%2FSource%2FDynamics%2FJoints%2Fb2RevoluteJoint.cpp;fp=Box2D%2FSource%2FDynamics%2FJoints%2Fb2RevoluteJoint.cpp;h=4fcc17ae363a75209e0a0cfbbc34c65b122a40ad;hb=f4dacbe0a45b6d24b5c0c0f30634988c71bc321d;hp=0000000000000000000000000000000000000000;hpb=1ef80d0d5bf4d1fc254fb1d05ad4e448645d5895;p=blok diff --git a/Box2D/Source/Dynamics/Joints/b2RevoluteJoint.cpp b/Box2D/Source/Dynamics/Joints/b2RevoluteJoint.cpp new file mode 100644 index 0000000..4fcc17a --- /dev/null +++ b/Box2D/Source/Dynamics/Joints/b2RevoluteJoint.cpp @@ -0,0 +1,399 @@ +/* +* Copyright (c) 2006-2007 Erin Catto http://www.gphysics.com +* +* 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 "b2RevoluteJoint.h" +#include "../b2Body.h" +#include "../b2World.h" + +#include "../b2Island.h" + +// Point-to-point constraint +// C = p2 - p1 +// Cdot = v2 - v1 +// = v2 + cross(w2, r2) - v1 - cross(w1, r1) +// J = [-I -r1_skew I r2_skew ] +// Identity used: +// w k % (rx i + ry j) = w * (-ry i + rx j) + +// Motor constraint +// Cdot = w2 - w1 +// J = [0 0 -1 0 0 1] +// K = invI1 + invI2 + +void b2RevoluteJointDef::Initialize(b2Body* b1, b2Body* b2, const b2Vec2& anchor) +{ + body1 = b1; + body2 = b2; + localAnchor1 = body1->GetLocalPoint(anchor); + localAnchor2 = body2->GetLocalPoint(anchor); + referenceAngle = body2->GetAngle() - body1->GetAngle(); +} + +b2RevoluteJoint::b2RevoluteJoint(const b2RevoluteJointDef* def) +: b2Joint(def) +{ + m_localAnchor1 = def->localAnchor1; + m_localAnchor2 = def->localAnchor2; + m_referenceAngle = def->referenceAngle; + + m_pivotForce.Set(0.0f, 0.0f); + m_motorForce = 0.0f; + m_limitForce = 0.0f; + m_limitPositionImpulse = 0.0f; + + m_lowerAngle = def->lowerAngle; + m_upperAngle = def->upperAngle; + m_maxMotorTorque = def->maxMotorTorque; + m_motorSpeed = def->motorSpeed; + m_enableLimit = def->enableLimit; + m_enableMotor = def->enableMotor; +} + +void b2RevoluteJoint::InitVelocityConstraints(const b2TimeStep& step) +{ + b2Body* b1 = m_body1; + b2Body* b2 = m_body2; + + // Compute the effective mass matrix. + b2Vec2 r1 = b2Mul(b1->GetXForm().R, m_localAnchor1 - b1->GetLocalCenter()); + b2Vec2 r2 = b2Mul(b2->GetXForm().R, m_localAnchor2 - b2->GetLocalCenter()); + + // K = [(1/m1 + 1/m2) * eye(2) - skew(r1) * invI1 * skew(r1) - skew(r2) * invI2 * skew(r2)] + // = [1/m1+1/m2 0 ] + invI1 * [r1.y*r1.y -r1.x*r1.y] + invI2 * [r1.y*r1.y -r1.x*r1.y] + // [ 0 1/m1+1/m2] [-r1.x*r1.y r1.x*r1.x] [-r1.x*r1.y r1.x*r1.x] + float32 invMass1 = b1->m_invMass, invMass2 = b2->m_invMass; + float32 invI1 = b1->m_invI, invI2 = b2->m_invI; + + b2Mat22 K1; + K1.col1.x = invMass1 + invMass2; K1.col2.x = 0.0f; + K1.col1.y = 0.0f; K1.col2.y = invMass1 + invMass2; + + b2Mat22 K2; + K2.col1.x = invI1 * r1.y * r1.y; K2.col2.x = -invI1 * r1.x * r1.y; + K2.col1.y = -invI1 * r1.x * r1.y; K2.col2.y = invI1 * r1.x * r1.x; + + b2Mat22 K3; + K3.col1.x = invI2 * r2.y * r2.y; K3.col2.x = -invI2 * r2.x * r2.y; + K3.col1.y = -invI2 * r2.x * r2.y; K3.col2.y = invI2 * r2.x * r2.x; + + b2Mat22 K = K1 + K2 + K3; + m_pivotMass = K.Invert(); + + m_motorMass = 1.0f / (invI1 + invI2); + + if (m_enableMotor == false) + { + m_motorForce = 0.0f; + } + + if (m_enableLimit) + { + float32 jointAngle = b2->m_sweep.a - b1->m_sweep.a - m_referenceAngle; + if (b2Abs(m_upperAngle - m_lowerAngle) < 2.0f * b2_angularSlop) + { + m_limitState = e_equalLimits; + } + else if (jointAngle <= m_lowerAngle) + { + if (m_limitState != e_atLowerLimit) + { + m_limitForce = 0.0f; + } + m_limitState = e_atLowerLimit; + } + else if (jointAngle >= m_upperAngle) + { + if (m_limitState != e_atUpperLimit) + { + m_limitForce = 0.0f; + } + m_limitState = e_atUpperLimit; + } + else + { + m_limitState = e_inactiveLimit; + m_limitForce = 0.0f; + } + } + else + { + m_limitForce = 0.0f; + } + + if (step.warmStarting) + { + b1->m_linearVelocity -= B2FORCE_SCALE(step.dt) * invMass1 * m_pivotForce; + b1->m_angularVelocity -= B2FORCE_SCALE(step.dt) * invI1 * (b2Cross(r1, m_pivotForce) + B2FORCE_INV_SCALE(m_motorForce + m_limitForce)); + + b2->m_linearVelocity += B2FORCE_SCALE(step.dt) * invMass2 * m_pivotForce; + b2->m_angularVelocity += B2FORCE_SCALE(step.dt) * invI2 * (b2Cross(r2, m_pivotForce) + B2FORCE_INV_SCALE(m_motorForce + m_limitForce)); + } + else + { + m_pivotForce.SetZero(); + m_motorForce = 0.0f; + m_limitForce = 0.0f; + } + + m_limitPositionImpulse = 0.0f; +} + +void b2RevoluteJoint::SolveVelocityConstraints(const b2TimeStep& step) +{ + b2Body* b1 = m_body1; + b2Body* b2 = m_body2; + + b2Vec2 r1 = b2Mul(b1->GetXForm().R, m_localAnchor1 - b1->GetLocalCenter()); + b2Vec2 r2 = b2Mul(b2->GetXForm().R, m_localAnchor2 - b2->GetLocalCenter()); + + // Solve point-to-point constraint + b2Vec2 pivotCdot = b2->m_linearVelocity + b2Cross(b2->m_angularVelocity, r2) - b1->m_linearVelocity - b2Cross(b1->m_angularVelocity, r1); + b2Vec2 pivotForce = -B2FORCE_INV_SCALE(step.inv_dt) * b2Mul(m_pivotMass, pivotCdot); + m_pivotForce += pivotForce; + + b2Vec2 P = B2FORCE_SCALE(step.dt) * pivotForce; + b1->m_linearVelocity -= b1->m_invMass * P; + b1->m_angularVelocity -= b1->m_invI * b2Cross(r1, P); + + b2->m_linearVelocity += b2->m_invMass * P; + b2->m_angularVelocity += b2->m_invI * b2Cross(r2, P); + + if (m_enableMotor && m_limitState != e_equalLimits) + { + float32 motorCdot = b2->m_angularVelocity - b1->m_angularVelocity - m_motorSpeed; + float32 motorForce = -step.inv_dt * m_motorMass * motorCdot; + float32 oldMotorForce = m_motorForce; + m_motorForce = b2Clamp(m_motorForce + motorForce, -m_maxMotorTorque, m_maxMotorTorque); + motorForce = m_motorForce - oldMotorForce; + + float32 P = step.dt * motorForce; + b1->m_angularVelocity -= b1->m_invI * P; + b2->m_angularVelocity += b2->m_invI * P; + } + + if (m_enableLimit && m_limitState != e_inactiveLimit) + { + float32 limitCdot = b2->m_angularVelocity - b1->m_angularVelocity; + float32 limitForce = -step.inv_dt * m_motorMass * limitCdot; + + if (m_limitState == e_equalLimits) + { + m_limitForce += limitForce; + } + else if (m_limitState == e_atLowerLimit) + { + float32 oldLimitForce = m_limitForce; + m_limitForce = b2Max(m_limitForce + limitForce, 0.0f); + limitForce = m_limitForce - oldLimitForce; + } + else if (m_limitState == e_atUpperLimit) + { + float32 oldLimitForce = m_limitForce; + m_limitForce = b2Min(m_limitForce + limitForce, 0.0f); + limitForce = m_limitForce - oldLimitForce; + } + + float32 P = step.dt * limitForce; + b1->m_angularVelocity -= b1->m_invI * P; + b2->m_angularVelocity += b2->m_invI * P; + } +} + +bool b2RevoluteJoint::SolvePositionConstraints() +{ + b2Body* b1 = m_body1; + b2Body* b2 = m_body2; + + float32 positionError = 0.0f; + + // Solve point-to-point position error. + b2Vec2 r1 = b2Mul(b1->GetXForm().R, m_localAnchor1 - b1->GetLocalCenter()); + b2Vec2 r2 = b2Mul(b2->GetXForm().R, m_localAnchor2 - b2->GetLocalCenter()); + + b2Vec2 p1 = b1->m_sweep.c + r1; + b2Vec2 p2 = b2->m_sweep.c + r2; + b2Vec2 ptpC = p2 - p1; + + positionError = ptpC.Length(); + + // Prevent overly large corrections. + //b2Vec2 dpMax(b2_maxLinearCorrection, b2_maxLinearCorrection); + //ptpC = b2Clamp(ptpC, -dpMax, dpMax); + + float32 invMass1 = b1->m_invMass, invMass2 = b2->m_invMass; + float32 invI1 = b1->m_invI, invI2 = b2->m_invI; + + b2Mat22 K1; + K1.col1.x = invMass1 + invMass2; K1.col2.x = 0.0f; + K1.col1.y = 0.0f; K1.col2.y = invMass1 + invMass2; + + b2Mat22 K2; + K2.col1.x = invI1 * r1.y * r1.y; K2.col2.x = -invI1 * r1.x * r1.y; + K2.col1.y = -invI1 * r1.x * r1.y; K2.col2.y = invI1 * r1.x * r1.x; + + b2Mat22 K3; + K3.col1.x = invI2 * r2.y * r2.y; K3.col2.x = -invI2 * r2.x * r2.y; + K3.col1.y = -invI2 * r2.x * r2.y; K3.col2.y = invI2 * r2.x * r2.x; + + b2Mat22 K = K1 + K2 + K3; + b2Vec2 impulse = K.Solve(-ptpC); + + b1->m_sweep.c -= b1->m_invMass * impulse; + b1->m_sweep.a -= b1->m_invI * b2Cross(r1, impulse); + + b2->m_sweep.c += b2->m_invMass * impulse; + b2->m_sweep.a += b2->m_invI * b2Cross(r2, impulse); + + b1->SynchronizeTransform(); + b2->SynchronizeTransform(); + + // Handle limits. + float32 angularError = 0.0f; + + if (m_enableLimit && m_limitState != e_inactiveLimit) + { + float32 angle = b2->m_sweep.a - b1->m_sweep.a - m_referenceAngle; + float32 limitImpulse = 0.0f; + + if (m_limitState == e_equalLimits) + { + // Prevent large angular corrections + float32 limitC = b2Clamp(angle, -b2_maxAngularCorrection, b2_maxAngularCorrection); + limitImpulse = -m_motorMass * limitC; + angularError = b2Abs(limitC); + } + else if (m_limitState == e_atLowerLimit) + { + float32 limitC = angle - m_lowerAngle; + angularError = b2Max(0.0f, -limitC); + + // Prevent large angular corrections and allow some slop. + limitC = b2Clamp(limitC + b2_angularSlop, -b2_maxAngularCorrection, 0.0f); + limitImpulse = -m_motorMass * limitC; + float32 oldLimitImpulse = m_limitPositionImpulse; + m_limitPositionImpulse = b2Max(m_limitPositionImpulse + limitImpulse, 0.0f); + limitImpulse = m_limitPositionImpulse - oldLimitImpulse; + } + else if (m_limitState == e_atUpperLimit) + { + float32 limitC = angle - m_upperAngle; + angularError = b2Max(0.0f, limitC); + + // Prevent large angular corrections and allow some slop. + limitC = b2Clamp(limitC - b2_angularSlop, 0.0f, b2_maxAngularCorrection); + limitImpulse = -m_motorMass * limitC; + float32 oldLimitImpulse = m_limitPositionImpulse; + m_limitPositionImpulse = b2Min(m_limitPositionImpulse + limitImpulse, 0.0f); + limitImpulse = m_limitPositionImpulse - oldLimitImpulse; + } + + b1->m_sweep.a -= b1->m_invI * limitImpulse; + b2->m_sweep.a += b2->m_invI * limitImpulse; + + b1->SynchronizeTransform(); + b2->SynchronizeTransform(); + } + + return positionError <= b2_linearSlop && angularError <= b2_angularSlop; +} + +b2Vec2 b2RevoluteJoint::GetAnchor1() const +{ + return m_body1->GetWorldPoint(m_localAnchor1); +} + +b2Vec2 b2RevoluteJoint::GetAnchor2() const +{ + return m_body2->GetWorldPoint(m_localAnchor2); +} + +b2Vec2 b2RevoluteJoint::GetReactionForce() const +{ + return B2FORCE_SCALE(float32(1.0))*m_pivotForce; +} + +float32 b2RevoluteJoint::GetReactionTorque() const +{ + return m_limitForce; +} + +float32 b2RevoluteJoint::GetJointAngle() const +{ + b2Body* b1 = m_body1; + b2Body* b2 = m_body2; + return b2->m_sweep.a - b1->m_sweep.a - m_referenceAngle; +} + +float32 b2RevoluteJoint::GetJointSpeed() const +{ + b2Body* b1 = m_body1; + b2Body* b2 = m_body2; + return b2->m_angularVelocity - b1->m_angularVelocity; +} + +bool b2RevoluteJoint::IsMotorEnabled() const +{ + return m_enableMotor; +} + +void b2RevoluteJoint::EnableMotor(bool flag) +{ + m_enableMotor = flag; +} + +float32 b2RevoluteJoint::GetMotorTorque() const +{ + return m_motorForce; +} + +void b2RevoluteJoint::SetMotorSpeed(float32 speed) +{ + m_motorSpeed = speed; +} + +void b2RevoluteJoint::SetMaxMotorTorque(float32 torque) +{ + m_maxMotorTorque = torque; +} + +bool b2RevoluteJoint::IsLimitEnabled() const +{ + return m_enableLimit; +} + +void b2RevoluteJoint::EnableLimit(bool flag) +{ + m_enableLimit = flag; +} + +float32 b2RevoluteJoint::GetLowerLimit() const +{ + return m_lowerAngle; +} + +float32 b2RevoluteJoint::GetUpperLimit() const +{ + return m_upperAngle; +} + +void b2RevoluteJoint::SetLimits(float32 lower, float32 upper) +{ + b2Assert(lower <= upper); + m_lowerAngle = lower; + m_upperAngle = upper; +}