paulxstretch/deps/juce/modules/juce_box2d/box2d/Dynamics/Joints/b2RopeJoint.cpp
essej 25bd5d8adb git subrepo clone --branch=sono6good https://github.com/essej/JUCE.git deps/juce
subrepo:
  subdir:   "deps/juce"
  merged:   "b13f9084e"
upstream:
  origin:   "https://github.com/essej/JUCE.git"
  branch:   "sono6good"
  commit:   "b13f9084e"
git-subrepo:
  version:  "0.4.3"
  origin:   "https://github.com/ingydotnet/git-subrepo.git"
  commit:   "2f68596"
2022-04-18 17:51:22 -04:00

242 lines
6.4 KiB
C++

/*
* Copyright (c) 2007-2011 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 "b2RopeJoint.h"
#include "../b2Body.h"
#include "../b2TimeStep.h"
// Limit:
// C = norm(pB - pA) - L
// u = (pB - pA) / norm(pB - pA)
// Cdot = dot(u, vB + cross(wB, rB) - vA - cross(wA, rA))
// J = [-u -cross(rA, u) u cross(rB, u)]
// K = J * invM * JT
// = invMassA + invIA * cross(rA, u)^2 + invMassB + invIB * cross(rB, u)^2
b2RopeJoint::b2RopeJoint(const b2RopeJointDef* def)
: b2Joint(def)
{
m_localAnchorA = def->localAnchorA;
m_localAnchorB = def->localAnchorB;
m_maxLength = def->maxLength;
m_mass = 0.0f;
m_impulse = 0.0f;
m_state = e_inactiveLimit;
m_length = 0.0f;
}
void b2RopeJoint::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;
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);
m_rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
m_rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
m_u = cB + m_rB - cA - m_rA;
m_length = m_u.Length();
float32 C = m_length - m_maxLength;
if (C > 0.0f)
{
m_state = e_atUpperLimit;
}
else
{
m_state = e_inactiveLimit;
}
if (m_length > b2_linearSlop)
{
m_u *= 1.0f / m_length;
}
else
{
m_u.SetZero();
m_mass = 0.0f;
m_impulse = 0.0f;
return;
}
// Compute effective mass.
float32 crA = b2Cross(m_rA, m_u);
float32 crB = b2Cross(m_rB, m_u);
float32 invMass = m_invMassA + m_invIA * crA * crA + m_invMassB + m_invIB * crB * crB;
m_mass = invMass != 0.0f ? 1.0f / invMass : 0.0f;
if (data.step.warmStarting)
{
// Scale the impulse to support a variable time step.
m_impulse *= data.step.dtRatio;
b2Vec2 P = m_impulse * m_u;
vA -= m_invMassA * P;
wA -= m_invIA * b2Cross(m_rA, P);
vB += m_invMassB * P;
wB += m_invIB * b2Cross(m_rB, P);
}
else
{
m_impulse = 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 b2RopeJoint::SolveVelocityConstraints(const b2SolverData& data)
{
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;
// Cdot = dot(u, v + cross(w, r))
b2Vec2 vpA = vA + b2Cross(wA, m_rA);
b2Vec2 vpB = vB + b2Cross(wB, m_rB);
float32 C = m_length - m_maxLength;
float32 Cdot = b2Dot(m_u, vpB - vpA);
// Predictive constraint.
if (C < 0.0f)
{
Cdot += data.step.inv_dt * C;
}
float32 impulse = -m_mass * Cdot;
float32 oldImpulse = m_impulse;
m_impulse = b2Min(0.0f, m_impulse + impulse);
impulse = m_impulse - oldImpulse;
b2Vec2 P = impulse * m_u;
vA -= m_invMassA * P;
wA -= m_invIA * b2Cross(m_rA, P);
vB += m_invMassB * P;
wB += m_invIB * b2Cross(m_rB, P);
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 b2RopeJoint::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 u = cB + rB - cA - rA;
float32 length = u.Normalize();
float32 C = length - m_maxLength;
C = b2Clamp(C, 0.0f, b2_maxLinearCorrection);
float32 impulse = -m_mass * C;
b2Vec2 P = impulse * u;
cA -= m_invMassA * P;
aA -= m_invIA * b2Cross(rA, P);
cB += m_invMassB * P;
aB += m_invIB * b2Cross(rB, P);
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 length - m_maxLength < b2_linearSlop;
}
b2Vec2 b2RopeJoint::GetAnchorA() const
{
return m_bodyA->GetWorldPoint(m_localAnchorA);
}
b2Vec2 b2RopeJoint::GetAnchorB() const
{
return m_bodyB->GetWorldPoint(m_localAnchorB);
}
b2Vec2 b2RopeJoint::GetReactionForce(float32 inv_dt) const
{
b2Vec2 F = (inv_dt * m_impulse) * m_u;
return F;
}
float32 b2RopeJoint::GetReactionTorque(float32 inv_dt) const
{
B2_NOT_USED(inv_dt);
return 0.0f;
}
float32 b2RopeJoint::GetMaxLength() const
{
return m_maxLength;
}
b2LimitState b2RopeJoint::GetLimitState() const
{
return m_state;
}
void b2RopeJoint::Dump()
{
int32 indexA = m_bodyA->m_islandIndex;
int32 indexB = m_bodyB->m_islandIndex;
b2Log(" b2RopeJointDef 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.maxLength = %.15lef;\n", m_maxLength);
b2Log(" joints[%d] = m_world->CreateJoint(&jd);\n", m_index);
}