b2PrismaticJoint.cpp
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00001 /*
00002 * Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
00003 *
00004 * This software is provided 'as-is', without any express or implied
00005 * warranty.  In no event will the authors be held liable for any damages
00006 * arising from the use of this software.
00007 * Permission is granted to anyone to use this software for any purpose,
00008 * including commercial applications, and to alter it and redistribute it
00009 * freely, subject to the following restrictions:
00010 * 1. The origin of this software must not be misrepresented; you must not
00011 * claim that you wrote the original software. If you use this software
00012 * in a product, an acknowledgment in the product documentation would be
00013 * appreciated but is not required.
00014 * 2. Altered source versions must be plainly marked as such, and must not be
00015 * misrepresented as being the original software.
00016 * 3. This notice may not be removed or altered from any source distribution.
00017 */
00018 
00019 #include <Box2D/Dynamics/Joints/b2PrismaticJoint.h>
00020 #include <Box2D/Dynamics/b2Body.h>
00021 #include <Box2D/Dynamics/b2TimeStep.h>
00022 
00023 // Linear constraint (point-to-line)
00024 // d = p2 - p1 = x2 + r2 - x1 - r1
00025 // C = dot(perp, d)
00026 // Cdot = dot(d, cross(w1, perp)) + dot(perp, v2 + cross(w2, r2) - v1 - cross(w1, r1))
00027 //      = -dot(perp, v1) - dot(cross(d + r1, perp), w1) + dot(perp, v2) + dot(cross(r2, perp), v2)
00028 // J = [-perp, -cross(d + r1, perp), perp, cross(r2,perp)]
00029 //
00030 // Angular constraint
00031 // C = a2 - a1 + a_initial
00032 // Cdot = w2 - w1
00033 // J = [0 0 -1 0 0 1]
00034 //
00035 // K = J * invM * JT
00036 //
00037 // J = [-a -s1 a s2]
00038 //     [0  -1  0  1]
00039 // a = perp
00040 // s1 = cross(d + r1, a) = cross(p2 - x1, a)
00041 // s2 = cross(r2, a) = cross(p2 - x2, a)
00042 
00043 
00044 // Motor/Limit linear constraint
00045 // C = dot(ax1, d)
00046 // Cdot = = -dot(ax1, v1) - dot(cross(d + r1, ax1), w1) + dot(ax1, v2) + dot(cross(r2, ax1), v2)
00047 // J = [-ax1 -cross(d+r1,ax1) ax1 cross(r2,ax1)]
00048 
00049 // Block Solver
00050 // We develop a block solver that includes the joint limit. This makes the limit stiff (inelastic) even
00051 // when the mass has poor distribution (leading to large torques about the joint anchor points).
00052 //
00053 // The Jacobian has 3 rows:
00054 // J = [-uT -s1 uT s2] // linear
00055 //     [0   -1   0  1] // angular
00056 //     [-vT -a1 vT a2] // limit
00057 //
00058 // u = perp
00059 // v = axis
00060 // s1 = cross(d + r1, u), s2 = cross(r2, u)
00061 // a1 = cross(d + r1, v), a2 = cross(r2, v)
00062 
00063 // M * (v2 - v1) = JT * df
00064 // J * v2 = bias
00065 //
00066 // v2 = v1 + invM * JT * df
00067 // J * (v1 + invM * JT * df) = bias
00068 // K * df = bias - J * v1 = -Cdot
00069 // K = J * invM * JT
00070 // Cdot = J * v1 - bias
00071 //
00072 // Now solve for f2.
00073 // df = f2 - f1
00074 // K * (f2 - f1) = -Cdot
00075 // f2 = invK * (-Cdot) + f1
00076 //
00077 // Clamp accumulated limit impulse.
00078 // lower: f2(3) = max(f2(3), 0)
00079 // upper: f2(3) = min(f2(3), 0)
00080 //
00081 // Solve for correct f2(1:2)
00082 // K(1:2, 1:2) * f2(1:2) = -Cdot(1:2) - K(1:2,3) * f2(3) + K(1:2,1:3) * f1
00083 //                       = -Cdot(1:2) - K(1:2,3) * f2(3) + K(1:2,1:2) * f1(1:2) + K(1:2,3) * f1(3)
00084 // K(1:2, 1:2) * f2(1:2) = -Cdot(1:2) - K(1:2,3) * (f2(3) - f1(3)) + K(1:2,1:2) * f1(1:2)
00085 // f2(1:2) = invK(1:2,1:2) * (-Cdot(1:2) - K(1:2,3) * (f2(3) - f1(3))) + f1(1:2)
00086 //
00087 // Now compute impulse to be applied:
00088 // df = f2 - f1
00089 
00090 void b2PrismaticJointDef::Initialize(b2Body* bA, b2Body* bB, const b2Vec2& anchor, const b2Vec2& axis)
00091 {
00092         bodyA = bA;
00093         bodyB = bB;
00094         localAnchorA = bodyA->GetLocalPoint(anchor);
00095         localAnchorB = bodyB->GetLocalPoint(anchor);
00096         localAxisA = bodyA->GetLocalVector(axis);
00097         referenceAngle = bodyB->GetAngle() - bodyA->GetAngle();
00098 }
00099 
00100 b2PrismaticJoint::b2PrismaticJoint(const b2PrismaticJointDef* def)
00101 : b2Joint(def)
00102 {
00103         m_localAnchorA = def->localAnchorA;
00104         m_localAnchorB = def->localAnchorB;
00105         m_localXAxisA = def->localAxisA;
00106         m_localXAxisA.Normalize();
00107         m_localYAxisA = b2Cross(1.0f, m_localXAxisA);
00108         m_referenceAngle = def->referenceAngle;
00109 
00110         m_impulse.SetZero();
00111         m_motorMass = 0.0f;
00112         m_motorImpulse = 0.0f;
00113 
00114         m_lowerTranslation = def->lowerTranslation;
00115         m_upperTranslation = def->upperTranslation;
00116         m_maxMotorForce = def->maxMotorForce;
00117         m_motorSpeed = def->motorSpeed;
00118         m_enableLimit = def->enableLimit;
00119         m_enableMotor = def->enableMotor;
00120         m_limitState = e_inactiveLimit;
00121 
00122         m_axis.SetZero();
00123         m_perp.SetZero();
00124 }
00125 
00126 void b2PrismaticJoint::InitVelocityConstraints(const b2SolverData& data)
00127 {
00128         m_indexA = m_bodyA->m_islandIndex;
00129         m_indexB = m_bodyB->m_islandIndex;
00130         m_localCenterA = m_bodyA->m_sweep.localCenter;
00131         m_localCenterB = m_bodyB->m_sweep.localCenter;
00132         m_invMassA = m_bodyA->m_invMass;
00133         m_invMassB = m_bodyB->m_invMass;
00134         m_invIA = m_bodyA->m_invI;
00135         m_invIB = m_bodyB->m_invI;
00136 
00137         b2Vec2 cA = data.positions[m_indexA].c;
00138         float32 aA = data.positions[m_indexA].a;
00139         b2Vec2 vA = data.velocities[m_indexA].v;
00140         float32 wA = data.velocities[m_indexA].w;
00141 
00142         b2Vec2 cB = data.positions[m_indexB].c;
00143         float32 aB = data.positions[m_indexB].a;
00144         b2Vec2 vB = data.velocities[m_indexB].v;
00145         float32 wB = data.velocities[m_indexB].w;
00146 
00147         b2Rot qA(aA), qB(aB);
00148 
00149         // Compute the effective masses.
00150         b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
00151         b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
00152         b2Vec2 d = (cB - cA) + rB - rA;
00153 
00154         float32 mA = m_invMassA, mB = m_invMassB;
00155         float32 iA = m_invIA, iB = m_invIB;
00156 
00157         // Compute motor Jacobian and effective mass.
00158         {
00159                 m_axis = b2Mul(qA, m_localXAxisA);
00160                 m_a1 = b2Cross(d + rA, m_axis);
00161                 m_a2 = b2Cross(rB, m_axis);
00162 
00163                 m_motorMass = mA + mB + iA * m_a1 * m_a1 + iB * m_a2 * m_a2;
00164                 if (m_motorMass > 0.0f)
00165                 {
00166                         m_motorMass = 1.0f / m_motorMass;
00167                 }
00168         }
00169 
00170         // Prismatic constraint.
00171         {
00172                 m_perp = b2Mul(qA, m_localYAxisA);
00173 
00174                 m_s1 = b2Cross(d + rA, m_perp);
00175                 m_s2 = b2Cross(rB, m_perp);
00176 
00177         float32 s1test;
00178         s1test = b2Cross(rA, m_perp);
00179 
00180                 float32 k11 = mA + mB + iA * m_s1 * m_s1 + iB * m_s2 * m_s2;
00181                 float32 k12 = iA * m_s1 + iB * m_s2;
00182                 float32 k13 = iA * m_s1 * m_a1 + iB * m_s2 * m_a2;
00183                 float32 k22 = iA + iB;
00184                 if (k22 == 0.0f)
00185                 {
00186                         // For bodies with fixed rotation.
00187                         k22 = 1.0f;
00188                 }
00189                 float32 k23 = iA * m_a1 + iB * m_a2;
00190                 float32 k33 = mA + mB + iA * m_a1 * m_a1 + iB * m_a2 * m_a2;
00191 
00192                 m_K.ex.Set(k11, k12, k13);
00193                 m_K.ey.Set(k12, k22, k23);
00194                 m_K.ez.Set(k13, k23, k33);
00195         }
00196 
00197         // Compute motor and limit terms.
00198         if (m_enableLimit)
00199         {
00200                 float32 jointTranslation = b2Dot(m_axis, d);
00201                 if (b2Abs(m_upperTranslation - m_lowerTranslation) < 2.0f * b2_linearSlop)
00202                 {
00203                         m_limitState = e_equalLimits;
00204                 }
00205                 else if (jointTranslation <= m_lowerTranslation)
00206                 {
00207                         if (m_limitState != e_atLowerLimit)
00208                         {
00209                                 m_limitState = e_atLowerLimit;
00210                                 m_impulse.z = 0.0f;
00211                         }
00212                 }
00213                 else if (jointTranslation >= m_upperTranslation)
00214                 {
00215                         if (m_limitState != e_atUpperLimit)
00216                         {
00217                                 m_limitState = e_atUpperLimit;
00218                                 m_impulse.z = 0.0f;
00219                         }
00220                 }
00221                 else
00222                 {
00223                         m_limitState = e_inactiveLimit;
00224                         m_impulse.z = 0.0f;
00225                 }
00226         }
00227         else
00228         {
00229                 m_limitState = e_inactiveLimit;
00230                 m_impulse.z = 0.0f;
00231         }
00232 
00233         if (m_enableMotor == false)
00234         {
00235                 m_motorImpulse = 0.0f;
00236         }
00237 
00238         if (data.step.warmStarting)
00239         {
00240                 // Account for variable time step.
00241                 m_impulse *= data.step.dtRatio;
00242                 m_motorImpulse *= data.step.dtRatio;
00243 
00244                 b2Vec2 P = m_impulse.x * m_perp + (m_motorImpulse + m_impulse.z) * m_axis;
00245                 float32 LA = m_impulse.x * m_s1 + m_impulse.y + (m_motorImpulse + m_impulse.z) * m_a1;
00246                 float32 LB = m_impulse.x * m_s2 + m_impulse.y + (m_motorImpulse + m_impulse.z) * m_a2;
00247 
00248                 vA -= mA * P;
00249                 wA -= iA * LA;
00250 
00251                 vB += mB * P;
00252                 wB += iB * LB;
00253         }
00254         else
00255         {
00256                 m_impulse.SetZero();
00257                 m_motorImpulse = 0.0f;
00258         }
00259 
00260         data.velocities[m_indexA].v = vA;
00261         data.velocities[m_indexA].w = wA;
00262         data.velocities[m_indexB].v = vB;
00263         data.velocities[m_indexB].w = wB;
00264 }
00265 
00266 void b2PrismaticJoint::SolveVelocityConstraints(const b2SolverData& data)
00267 {
00268         b2Vec2 vA = data.velocities[m_indexA].v;
00269         float32 wA = data.velocities[m_indexA].w;
00270         b2Vec2 vB = data.velocities[m_indexB].v;
00271         float32 wB = data.velocities[m_indexB].w;
00272 
00273         float32 mA = m_invMassA, mB = m_invMassB;
00274         float32 iA = m_invIA, iB = m_invIB;
00275 
00276         // Solve linear motor constraint.
00277         if (m_enableMotor && m_limitState != e_equalLimits)
00278         {
00279                 float32 Cdot = b2Dot(m_axis, vB - vA) + m_a2 * wB - m_a1 * wA;
00280                 float32 impulse = m_motorMass * (m_motorSpeed - Cdot);
00281                 float32 oldImpulse = m_motorImpulse;
00282                 float32 maxImpulse = data.step.dt * m_maxMotorForce;
00283                 m_motorImpulse = b2Clamp(m_motorImpulse + impulse, -maxImpulse, maxImpulse);
00284                 impulse = m_motorImpulse - oldImpulse;
00285 
00286                 b2Vec2 P = impulse * m_axis;
00287                 float32 LA = impulse * m_a1;
00288                 float32 LB = impulse * m_a2;
00289 
00290                 vA -= mA * P;
00291                 wA -= iA * LA;
00292 
00293                 vB += mB * P;
00294                 wB += iB * LB;
00295         }
00296 
00297         b2Vec2 Cdot1;
00298         Cdot1.x = b2Dot(m_perp, vB - vA) + m_s2 * wB - m_s1 * wA;
00299         Cdot1.y = wB - wA;
00300 
00301         if (m_enableLimit && m_limitState != e_inactiveLimit)
00302         {
00303                 // Solve prismatic and limit constraint in block form.
00304                 float32 Cdot2;
00305                 Cdot2 = b2Dot(m_axis, vB - vA) + m_a2 * wB - m_a1 * wA;
00306                 b2Vec3 Cdot(Cdot1.x, Cdot1.y, Cdot2);
00307 
00308                 b2Vec3 f1 = m_impulse;
00309                 b2Vec3 df =  m_K.Solve33(-Cdot);
00310                 m_impulse += df;
00311 
00312                 if (m_limitState == e_atLowerLimit)
00313                 {
00314                         m_impulse.z = b2Max(m_impulse.z, 0.0f);
00315                 }
00316                 else if (m_limitState == e_atUpperLimit)
00317                 {
00318                         m_impulse.z = b2Min(m_impulse.z, 0.0f);
00319                 }
00320 
00321                 // f2(1:2) = invK(1:2,1:2) * (-Cdot(1:2) - K(1:2,3) * (f2(3) - f1(3))) + f1(1:2)
00322                 b2Vec2 b = -Cdot1 - (m_impulse.z - f1.z) * b2Vec2(m_K.ez.x, m_K.ez.y);
00323                 b2Vec2 f2r = m_K.Solve22(b) + b2Vec2(f1.x, f1.y);
00324                 m_impulse.x = f2r.x;
00325                 m_impulse.y = f2r.y;
00326 
00327                 df = m_impulse - f1;
00328 
00329                 b2Vec2 P = df.x * m_perp + df.z * m_axis;
00330                 float32 LA = df.x * m_s1 + df.y + df.z * m_a1;
00331                 float32 LB = df.x * m_s2 + df.y + df.z * m_a2;
00332 
00333                 vA -= mA * P;
00334                 wA -= iA * LA;
00335 
00336                 vB += mB * P;
00337                 wB += iB * LB;
00338         }
00339         else
00340         {
00341                 // Limit is inactive, just solve the prismatic constraint in block form.
00342                 b2Vec2 df = m_K.Solve22(-Cdot1);
00343                 m_impulse.x += df.x;
00344                 m_impulse.y += df.y;
00345 
00346                 b2Vec2 P = df.x * m_perp;
00347                 float32 LA = df.x * m_s1 + df.y;
00348                 float32 LB = df.x * m_s2 + df.y;
00349 
00350                 vA -= mA * P;
00351                 wA -= iA * LA;
00352 
00353                 vB += mB * P;
00354                 wB += iB * LB;
00355         }
00356 
00357         data.velocities[m_indexA].v = vA;
00358         data.velocities[m_indexA].w = wA;
00359         data.velocities[m_indexB].v = vB;
00360         data.velocities[m_indexB].w = wB;
00361 }
00362 
00363 bool b2PrismaticJoint::SolvePositionConstraints(const b2SolverData& data)
00364 {
00365         b2Vec2 cA = data.positions[m_indexA].c;
00366         float32 aA = data.positions[m_indexA].a;
00367         b2Vec2 cB = data.positions[m_indexB].c;
00368         float32 aB = data.positions[m_indexB].a;
00369 
00370         b2Rot qA(aA), qB(aB);
00371 
00372         float32 mA = m_invMassA, mB = m_invMassB;
00373         float32 iA = m_invIA, iB = m_invIB;
00374 
00375         // Compute fresh Jacobians
00376         b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
00377         b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
00378         b2Vec2 d = cB + rB - cA - rA;
00379 
00380         b2Vec2 axis = b2Mul(qA, m_localXAxisA);
00381         float32 a1 = b2Cross(d + rA, axis);
00382         float32 a2 = b2Cross(rB, axis);
00383         b2Vec2 perp = b2Mul(qA, m_localYAxisA);
00384 
00385         float32 s1 = b2Cross(d + rA, perp);
00386         float32 s2 = b2Cross(rB, perp);
00387 
00388         b2Vec3 impulse;
00389         b2Vec2 C1;
00390         C1.x = b2Dot(perp, d);
00391         C1.y = aB - aA - m_referenceAngle;
00392 
00393         float32 linearError = b2Abs(C1.x);
00394         float32 angularError = b2Abs(C1.y);
00395 
00396         bool active = false;
00397         float32 C2 = 0.0f;
00398         if (m_enableLimit)
00399         {
00400                 float32 translation = b2Dot(axis, d);
00401                 if (b2Abs(m_upperTranslation - m_lowerTranslation) < 2.0f * b2_linearSlop)
00402                 {
00403                         // Prevent large angular corrections
00404                         C2 = b2Clamp(translation, -b2_maxLinearCorrection, b2_maxLinearCorrection);
00405                         linearError = b2Max(linearError, b2Abs(translation));
00406                         active = true;
00407                 }
00408                 else if (translation <= m_lowerTranslation)
00409                 {
00410                         // Prevent large linear corrections and allow some slop.
00411                         C2 = b2Clamp(translation - m_lowerTranslation + b2_linearSlop, -b2_maxLinearCorrection, 0.0f);
00412                         linearError = b2Max(linearError, m_lowerTranslation - translation);
00413                         active = true;
00414                 }
00415                 else if (translation >= m_upperTranslation)
00416                 {
00417                         // Prevent large linear corrections and allow some slop.
00418                         C2 = b2Clamp(translation - m_upperTranslation - b2_linearSlop, 0.0f, b2_maxLinearCorrection);
00419                         linearError = b2Max(linearError, translation - m_upperTranslation);
00420                         active = true;
00421                 }
00422         }
00423 
00424         if (active)
00425         {
00426                 float32 k11 = mA + mB + iA * s1 * s1 + iB * s2 * s2;
00427                 float32 k12 = iA * s1 + iB * s2;
00428                 float32 k13 = iA * s1 * a1 + iB * s2 * a2;
00429                 float32 k22 = iA + iB;
00430                 if (k22 == 0.0f)
00431                 {
00432                         // For fixed rotation
00433                         k22 = 1.0f;
00434                 }
00435                 float32 k23 = iA * a1 + iB * a2;
00436                 float32 k33 = mA + mB + iA * a1 * a1 + iB * a2 * a2;
00437 
00438                 b2Mat33 K;
00439                 K.ex.Set(k11, k12, k13);
00440                 K.ey.Set(k12, k22, k23);
00441                 K.ez.Set(k13, k23, k33);
00442 
00443                 b2Vec3 C;
00444                 C.x = C1.x;
00445                 C.y = C1.y;
00446                 C.z = C2;
00447 
00448                 impulse = K.Solve33(-C);
00449         }
00450         else
00451         {
00452                 float32 k11 = mA + mB + iA * s1 * s1 + iB * s2 * s2;
00453                 float32 k12 = iA * s1 + iB * s2;
00454                 float32 k22 = iA + iB;
00455                 if (k22 == 0.0f)
00456                 {
00457                         k22 = 1.0f;
00458                 }
00459 
00460                 b2Mat22 K;
00461                 K.ex.Set(k11, k12);
00462                 K.ey.Set(k12, k22);
00463 
00464                 b2Vec2 impulse1 = K.Solve(-C1);
00465                 impulse.x = impulse1.x;
00466                 impulse.y = impulse1.y;
00467                 impulse.z = 0.0f;
00468         }
00469 
00470         b2Vec2 P = impulse.x * perp + impulse.z * axis;
00471         float32 LA = impulse.x * s1 + impulse.y + impulse.z * a1;
00472         float32 LB = impulse.x * s2 + impulse.y + impulse.z * a2;
00473 
00474         cA -= mA * P;
00475         aA -= iA * LA;
00476         cB += mB * P;
00477         aB += iB * LB;
00478 
00479         data.positions[m_indexA].c = cA;
00480         data.positions[m_indexA].a = aA;
00481         data.positions[m_indexB].c = cB;
00482         data.positions[m_indexB].a = aB;
00483 
00484         return linearError <= b2_linearSlop && angularError <= b2_angularSlop;
00485 }
00486 
00487 b2Vec2 b2PrismaticJoint::GetAnchorA() const
00488 {
00489         return m_bodyA->GetWorldPoint(m_localAnchorA);
00490 }
00491 
00492 b2Vec2 b2PrismaticJoint::GetAnchorB() const
00493 {
00494         return m_bodyB->GetWorldPoint(m_localAnchorB);
00495 }
00496 
00497 b2Vec2 b2PrismaticJoint::GetReactionForce(float32 inv_dt) const
00498 {
00499         return inv_dt * (m_impulse.x * m_perp + (m_motorImpulse + m_impulse.z) * m_axis);
00500 }
00501 
00502 float32 b2PrismaticJoint::GetReactionTorque(float32 inv_dt) const
00503 {
00504         return inv_dt * m_impulse.y;
00505 }
00506 
00507 float32 b2PrismaticJoint::GetJointTranslation() const
00508 {
00509         b2Vec2 pA = m_bodyA->GetWorldPoint(m_localAnchorA);
00510         b2Vec2 pB = m_bodyB->GetWorldPoint(m_localAnchorB);
00511         b2Vec2 d = pB - pA;
00512         b2Vec2 axis = m_bodyA->GetWorldVector(m_localXAxisA);
00513 
00514         float32 translation = b2Dot(d, axis);
00515         return translation;
00516 }
00517 
00518 float32 b2PrismaticJoint::GetJointSpeed() const
00519 {
00520         b2Body* bA = m_bodyA;
00521         b2Body* bB = m_bodyB;
00522 
00523         b2Vec2 rA = b2Mul(bA->m_xf.q, m_localAnchorA - bA->m_sweep.localCenter);
00524         b2Vec2 rB = b2Mul(bB->m_xf.q, m_localAnchorB - bB->m_sweep.localCenter);
00525         b2Vec2 p1 = bA->m_sweep.c + rA;
00526         b2Vec2 p2 = bB->m_sweep.c + rB;
00527         b2Vec2 d = p2 - p1;
00528         b2Vec2 axis = b2Mul(bA->m_xf.q, m_localXAxisA);
00529 
00530         b2Vec2 vA = bA->m_linearVelocity;
00531         b2Vec2 vB = bB->m_linearVelocity;
00532         float32 wA = bA->m_angularVelocity;
00533         float32 wB = bB->m_angularVelocity;
00534 
00535         float32 speed = b2Dot(d, b2Cross(wA, axis)) + b2Dot(axis, vB + b2Cross(wB, rB) - vA - b2Cross(wA, rA));
00536         return speed;
00537 }
00538 
00539 bool b2PrismaticJoint::IsLimitEnabled() const
00540 {
00541         return m_enableLimit;
00542 }
00543 
00544 void b2PrismaticJoint::EnableLimit(bool flag)
00545 {
00546         if (flag != m_enableLimit)
00547         {
00548                 m_bodyA->SetAwake(true);
00549                 m_bodyB->SetAwake(true);
00550                 m_enableLimit = flag;
00551                 m_impulse.z = 0.0f;
00552         }
00553 }
00554 
00555 float32 b2PrismaticJoint::GetLowerLimit() const
00556 {
00557         return m_lowerTranslation;
00558 }
00559 
00560 float32 b2PrismaticJoint::GetUpperLimit() const
00561 {
00562         return m_upperTranslation;
00563 }
00564 
00565 void b2PrismaticJoint::SetLimits(float32 lower, float32 upper)
00566 {
00567         b2Assert(lower <= upper);
00568         if (lower != m_lowerTranslation || upper != m_upperTranslation)
00569         {
00570                 m_bodyA->SetAwake(true);
00571                 m_bodyB->SetAwake(true);
00572                 m_lowerTranslation = lower;
00573                 m_upperTranslation = upper;
00574                 m_impulse.z = 0.0f;
00575         }
00576 }
00577 
00578 bool b2PrismaticJoint::IsMotorEnabled() const
00579 {
00580         return m_enableMotor;
00581 }
00582 
00583 void b2PrismaticJoint::EnableMotor(bool flag)
00584 {
00585         m_bodyA->SetAwake(true);
00586         m_bodyB->SetAwake(true);
00587         m_enableMotor = flag;
00588 }
00589 
00590 void b2PrismaticJoint::SetMotorSpeed(float32 speed)
00591 {
00592         m_bodyA->SetAwake(true);
00593         m_bodyB->SetAwake(true);
00594         m_motorSpeed = speed;
00595 }
00596 
00597 void b2PrismaticJoint::SetMaxMotorForce(float32 force)
00598 {
00599         m_bodyA->SetAwake(true);
00600         m_bodyB->SetAwake(true);
00601         m_maxMotorForce = force;
00602 }
00603 
00604 float32 b2PrismaticJoint::GetMotorForce(float32 inv_dt) const
00605 {
00606         return inv_dt * m_motorImpulse;
00607 }
00608 
00609 void b2PrismaticJoint::Dump()
00610 {
00611         int32 indexA = m_bodyA->m_islandIndex;
00612         int32 indexB = m_bodyB->m_islandIndex;
00613 
00614         b2Log("  b2PrismaticJointDef jd;\n");
00615         b2Log("  jd.bodyA = bodies[%d];\n", indexA);
00616         b2Log("  jd.bodyB = bodies[%d];\n", indexB);
00617         b2Log("  jd.collideConnected = bool(%d);\n", m_collideConnected);
00618         b2Log("  jd.localAnchorA.Set(%.15lef, %.15lef);\n", m_localAnchorA.x, m_localAnchorA.y);
00619         b2Log("  jd.localAnchorB.Set(%.15lef, %.15lef);\n", m_localAnchorB.x, m_localAnchorB.y);
00620         b2Log("  jd.localAxisA.Set(%.15lef, %.15lef);\n", m_localXAxisA.x, m_localXAxisA.y);
00621         b2Log("  jd.referenceAngle = %.15lef;\n", m_referenceAngle);
00622         b2Log("  jd.enableLimit = bool(%d);\n", m_enableLimit);
00623         b2Log("  jd.lowerTranslation = %.15lef;\n", m_lowerTranslation);
00624         b2Log("  jd.upperTranslation = %.15lef;\n", m_upperTranslation);
00625         b2Log("  jd.enableMotor = bool(%d);\n", m_enableMotor);
00626         b2Log("  jd.motorSpeed = %.15lef;\n", m_motorSpeed);
00627         b2Log("  jd.maxMotorForce = %.15lef;\n", m_maxMotorForce);
00628         b2Log("  joints[%d] = m_world->CreateJoint(&jd);\n", m_index);
00629 }


mvsim
Author(s):
autogenerated on Thu Jun 6 2019 22:08:35