b2RopeJoint.cpp
Go to the documentation of this file.
1 /*
2 * Copyright (c) 2007-2011 Erin Catto http://www.box2d.org
3 *
4 * This software is provided 'as-is', without any express or implied
5 * warranty. In no event will the authors be held liable for any damages
6 * arising from the use of this software.
7 * Permission is granted to anyone to use this software for any purpose,
8 * including commercial applications, and to alter it and redistribute it
9 * freely, subject to the following restrictions:
10 * 1. The origin of this software must not be misrepresented; you must not
11 * claim that you wrote the original software. If you use this software
12 * in a product, an acknowledgment in the product documentation would be
13 * appreciated but is not required.
14 * 2. Altered source versions must be plainly marked as such, and must not be
15 * misrepresented as being the original software.
16 * 3. This notice may not be removed or altered from any source distribution.
17 */
18 
20 #include <Box2D/Dynamics/b2Body.h>
22 
23 
24 // Limit:
25 // C = norm(pB - pA) - L
26 // u = (pB - pA) / norm(pB - pA)
27 // Cdot = dot(u, vB + cross(wB, rB) - vA - cross(wA, rA))
28 // J = [-u -cross(rA, u) u cross(rB, u)]
29 // K = J * invM * JT
30 // = invMassA + invIA * cross(rA, u)^2 + invMassB + invIB * cross(rB, u)^2
31 
33 : b2Joint(def)
34 {
37 
38  m_maxLength = def->maxLength;
39 
40  m_mass = 0.0f;
41  m_impulse = 0.0f;
43  m_length = 0.0f;
44 }
45 
47 {
56 
57  b2Vec2 cA = data.positions[m_indexA].c;
58  float32 aA = data.positions[m_indexA].a;
59  b2Vec2 vA = data.velocities[m_indexA].v;
60  float32 wA = data.velocities[m_indexA].w;
61 
62  b2Vec2 cB = data.positions[m_indexB].c;
63  float32 aB = data.positions[m_indexB].a;
64  b2Vec2 vB = data.velocities[m_indexB].v;
65  float32 wB = data.velocities[m_indexB].w;
66 
67  b2Rot qA(aA), qB(aB);
68 
71  m_u = cB + m_rB - cA - m_rA;
72 
73  m_length = m_u.Length();
74 
76  if (C > 0.0f)
77  {
79  }
80  else
81  {
83  }
84 
85  if (m_length > b2_linearSlop)
86  {
87  m_u *= 1.0f / m_length;
88  }
89  else
90  {
91  m_u.SetZero();
92  m_mass = 0.0f;
93  m_impulse = 0.0f;
94  return;
95  }
96 
97  // Compute effective mass.
98  float32 crA = b2Cross(m_rA, m_u);
99  float32 crB = b2Cross(m_rB, m_u);
100  float32 invMass = m_invMassA + m_invIA * crA * crA + m_invMassB + m_invIB * crB * crB;
101 
102  m_mass = invMass != 0.0f ? 1.0f / invMass : 0.0f;
103 
104  if (data.step.warmStarting)
105  {
106  // Scale the impulse to support a variable time step.
107  m_impulse *= data.step.dtRatio;
108 
109  b2Vec2 P = m_impulse * m_u;
110  vA -= m_invMassA * P;
111  wA -= m_invIA * b2Cross(m_rA, P);
112  vB += m_invMassB * P;
113  wB += m_invIB * b2Cross(m_rB, P);
114  }
115  else
116  {
117  m_impulse = 0.0f;
118  }
119 
120  data.velocities[m_indexA].v = vA;
121  data.velocities[m_indexA].w = wA;
122  data.velocities[m_indexB].v = vB;
123  data.velocities[m_indexB].w = wB;
124 }
125 
127 {
128  b2Vec2 vA = data.velocities[m_indexA].v;
129  float32 wA = data.velocities[m_indexA].w;
130  b2Vec2 vB = data.velocities[m_indexB].v;
131  float32 wB = data.velocities[m_indexB].w;
132 
133  // Cdot = dot(u, v + cross(w, r))
134  b2Vec2 vpA = vA + b2Cross(wA, m_rA);
135  b2Vec2 vpB = vB + b2Cross(wB, m_rB);
137  float32 Cdot = b2Dot(m_u, vpB - vpA);
138 
139  // Predictive constraint.
140  if (C < 0.0f)
141  {
142  Cdot += data.step.inv_dt * C;
143  }
144 
145  float32 impulse = -m_mass * Cdot;
146  float32 oldImpulse = m_impulse;
147  m_impulse = b2Min(0.0f, m_impulse + impulse);
148  impulse = m_impulse - oldImpulse;
149 
150  b2Vec2 P = impulse * m_u;
151  vA -= m_invMassA * P;
152  wA -= m_invIA * b2Cross(m_rA, P);
153  vB += m_invMassB * P;
154  wB += m_invIB * b2Cross(m_rB, P);
155 
156  data.velocities[m_indexA].v = vA;
157  data.velocities[m_indexA].w = wA;
158  data.velocities[m_indexB].v = vB;
159  data.velocities[m_indexB].w = wB;
160 }
161 
163 {
164  b2Vec2 cA = data.positions[m_indexA].c;
165  float32 aA = data.positions[m_indexA].a;
166  b2Vec2 cB = data.positions[m_indexB].c;
167  float32 aB = data.positions[m_indexB].a;
168 
169  b2Rot qA(aA), qB(aB);
170 
173  b2Vec2 u = cB + rB - cA - rA;
174 
175  float32 length = u.Normalize();
176  float32 C = length - m_maxLength;
177 
178  C = b2Clamp(C, 0.0f, b2_maxLinearCorrection);
179 
180  float32 impulse = -m_mass * C;
181  b2Vec2 P = impulse * u;
182 
183  cA -= m_invMassA * P;
184  aA -= m_invIA * b2Cross(rA, P);
185  cB += m_invMassB * P;
186  aB += m_invIB * b2Cross(rB, P);
187 
188  data.positions[m_indexA].c = cA;
189  data.positions[m_indexA].a = aA;
190  data.positions[m_indexB].c = cB;
191  data.positions[m_indexB].a = aB;
192 
193  return length - m_maxLength < b2_linearSlop;
194 }
195 
197 {
199 }
200 
202 {
204 }
205 
207 {
208  b2Vec2 F = (inv_dt * m_impulse) * m_u;
209  return F;
210 }
211 
213 {
214  B2_NOT_USED(inv_dt);
215  return 0.0f;
216 }
217 
219 {
220  return m_maxLength;
221 }
222 
224 {
225  return m_state;
226 }
227 
229 {
230  int32 indexA = m_bodyA->m_islandIndex;
231  int32 indexB = m_bodyB->m_islandIndex;
232 
233  b2Log(" b2RopeJointDef jd;\n");
234  b2Log(" jd.bodyA = bodies[%d];\n", indexA);
235  b2Log(" jd.bodyB = bodies[%d];\n", indexB);
236  b2Log(" jd.collideConnected = bool(%d);\n", m_collideConnected);
237  b2Log(" jd.localAnchorA.Set(%.15lef, %.15lef);\n", m_localAnchorA.x, m_localAnchorA.y);
238  b2Log(" jd.localAnchorB.Set(%.15lef, %.15lef);\n", m_localAnchorB.x, m_localAnchorB.y);
239  b2Log(" jd.maxLength = %.15lef;\n", m_maxLength);
240  b2Log(" joints[%d] = m_world->CreateJoint(&jd);\n", m_index);
241 }
GLuint GLsizei GLsizei * length
float32 b2Dot(const b2Vec2 &a, const b2Vec2 &b)
Perform the dot product on two vectors.
Definition: b2Math.h:405
b2Velocity * velocities
Definition: b2TimeStep.h:67
float32 m_invMass
Definition: b2Body.h:455
int32 m_islandIndex
Definition: b2Body.h:434
b2Vec2 b2Mul(const b2Mat22 &A, const b2Vec2 &v)
Definition: b2Math.h:432
void b2Log(const char *string,...)
Logging function.
Definition: b2Settings.cpp:38
float32 a
Definition: b2TimeStep.h:52
#define b2_linearSlop
Definition: b2Settings.h:68
int32 m_indexA
Definition: b2RopeJoint.h:99
void Dump()
Dump joint to dmLog.
bool SolvePositionConstraints(const b2SolverData &data)
b2Vec2 localAnchorA
The local anchor point relative to bodyA&#39;s origin.
Definition: b2RopeJoint.h:39
b2TimeStep step
Definition: b2TimeStep.h:65
b2LimitState
Definition: b2Joint.h:45
b2Vec2 c
Definition: b2TimeStep.h:51
b2Vec2 m_u
Definition: b2RopeJoint.h:101
float32 w
Definition: b2TimeStep.h:59
bool m_collideConnected
Definition: b2Joint.h:181
#define B2_NOT_USED(x)
Definition: b2Settings.h:26
float32 dtRatio
Definition: b2TimeStep.h:42
b2Vec2 m_localAnchorA
Definition: b2RopeJoint.h:92
b2Vec2 GetWorldPoint(const b2Vec2 &localPoint) const
Definition: b2Body.h:556
b2Vec2 m_rA
Definition: b2RopeJoint.h:102
void InitVelocityConstraints(const b2SolverData &data)
Definition: b2RopeJoint.cpp:46
Solver Data.
Definition: b2TimeStep.h:63
void SetZero()
Set this vector to all zeros.
Definition: b2Math.h:61
float32 inv_dt
Definition: b2TimeStep.h:41
int32 m_index
Definition: b2Joint.h:178
A 2D column vector.
Definition: b2Math.h:52
b2Vec2 GetAnchorB() const
Get the anchor point on bodyB in world coordinates.
#define b2_maxLinearCorrection
Definition: b2Settings.h:94
signed int int32
Definition: b2Settings.h:31
b2Vec2 localCenter
local center of mass position
Definition: b2Math.h:392
float32 b2Cross(const b2Vec2 &a, const b2Vec2 &b)
Perform the cross product on two vectors. In 2D this produces a scalar.
Definition: b2Math.h:411
float32 m_impulse
Definition: b2RopeJoint.h:96
b2Vec2 m_rB
Definition: b2RopeJoint.h:103
b2Vec2 v
Definition: b2TimeStep.h:58
float32 m_maxLength
Definition: b2RopeJoint.h:94
b2LimitState GetLimitState() const
float32 m_invIA
Definition: b2RopeJoint.h:108
b2Vec2 m_localCenterB
Definition: b2RopeJoint.h:105
float32 maxLength
Definition: b2RopeJoint.h:47
float32 m_invI
Definition: b2Body.h:458
float32 m_mass
Definition: b2RopeJoint.h:110
GLint GLenum GLsizei GLint GLsizei const GLvoid * data
b2Vec2 m_localAnchorB
Definition: b2RopeJoint.h:93
float32 m_invMassB
Definition: b2RopeJoint.h:107
b2Vec2 localAnchorB
The local anchor point relative to bodyB&#39;s origin.
Definition: b2RopeJoint.h:42
int32 m_indexB
Definition: b2RopeJoint.h:100
b2Body * m_bodyA
Definition: b2Joint.h:175
void SolveVelocityConstraints(const b2SolverData &data)
b2RopeJoint(const b2RopeJointDef *data)
Definition: b2RopeJoint.cpp:32
float32 y
Definition: b2Math.h:139
b2Position * positions
Definition: b2TimeStep.h:66
float32 m_invIB
Definition: b2RopeJoint.h:109
T b2Clamp(T a, T low, T high)
Definition: b2Math.h:653
b2Vec2 GetReactionForce(float32 inv_dt) const
Get the reaction force on bodyB at the joint anchor in Newtons.
b2LimitState m_state
Definition: b2RopeJoint.h:111
float32 m_length
Definition: b2RopeJoint.h:95
float32 GetReactionTorque(float32 inv_dt) const
Get the reaction torque on bodyB in N*m.
bool warmStarting
Definition: b2TimeStep.h:45
Rotation.
Definition: b2Math.h:298
T b2Min(T a, T b)
Definition: b2Math.h:631
float32 m_invMassA
Definition: b2RopeJoint.h:106
float32 x
Definition: b2Math.h:139
float32 Normalize()
Convert this vector into a unit vector. Returns the length.
Definition: b2Math.h:113
b2Vec2 m_localCenterA
Definition: b2RopeJoint.h:104
float32 Length() const
Get the length of this vector (the norm).
Definition: b2Math.h:100
b2Vec2 GetAnchorA() const
Get the anchor point on bodyA in world coordinates.
float32 GetMaxLength() const
b2Body * m_bodyB
Definition: b2Joint.h:176
b2Sweep m_sweep
Definition: b2Body.h:437
float float32
Definition: b2Settings.h:35
CArrayDouble< 6 > C
GLdouble GLdouble GLdouble GLdouble GLdouble GLdouble f


mvsim
Author(s):
autogenerated on Fri May 7 2021 03:05:51