--- /dev/null
+/*
+* 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;
+}
projects / blok / blobdiff