paulxstretch/deps/juce/modules/juce_box2d/box2d/Dynamics/Joints/b2PulleyJoint.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

333 lines
8.6 KiB
C++

/*
* Copyright (c) 2007 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 "b2PulleyJoint.h"
#include "../b2Body.h"
#include "../b2TimeStep.h"
// Pulley:
// length1 = norm(p1 - s1)
// length2 = norm(p2 - s2)
// C0 = (length1 + ratio * length2)_initial
// C = C0 - (length1 + ratio * length2)
// u1 = (p1 - s1) / norm(p1 - s1)
// u2 = (p2 - s2) / norm(p2 - s2)
// Cdot = -dot(u1, v1 + cross(w1, r1)) - ratio * dot(u2, v2 + cross(w2, r2))
// J = -[u1 cross(r1, u1) ratio * u2 ratio * cross(r2, u2)]
// K = J * invM * JT
// = invMass1 + invI1 * cross(r1, u1)^2 + ratio^2 * (invMass2 + invI2 * cross(r2, u2)^2)
void b2PulleyJointDef::Initialize(b2Body* bA, b2Body* bB,
const b2Vec2& groundA, const b2Vec2& groundB,
const b2Vec2& anchorA, const b2Vec2& anchorB,
float32 r)
{
bodyA = bA;
bodyB = bB;
groundAnchorA = groundA;
groundAnchorB = groundB;
localAnchorA = bodyA->GetLocalPoint(anchorA);
localAnchorB = bodyB->GetLocalPoint(anchorB);
b2Vec2 dA = anchorA - groundA;
lengthA = dA.Length();
b2Vec2 dB = anchorB - groundB;
lengthB = dB.Length();
ratio = r;
b2Assert(ratio > b2_epsilon);
}
b2PulleyJoint::b2PulleyJoint(const b2PulleyJointDef* def)
: b2Joint(def)
{
m_groundAnchorA = def->groundAnchorA;
m_groundAnchorB = def->groundAnchorB;
m_localAnchorA = def->localAnchorA;
m_localAnchorB = def->localAnchorB;
m_lengthA = def->lengthA;
m_lengthB = def->lengthB;
b2Assert(def->ratio != 0.0f);
m_ratio = def->ratio;
m_constant = def->lengthA + m_ratio * def->lengthB;
m_impulse = 0.0f;
}
void b2PulleyJoint::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);
// Get the pulley axes.
m_uA = cA + m_rA - m_groundAnchorA;
m_uB = cB + m_rB - m_groundAnchorB;
float32 lengthA = m_uA.Length();
float32 lengthB = m_uB.Length();
if (lengthA > 10.0f * b2_linearSlop)
{
m_uA *= 1.0f / lengthA;
}
else
{
m_uA.SetZero();
}
if (lengthB > 10.0f * b2_linearSlop)
{
m_uB *= 1.0f / lengthB;
}
else
{
m_uB.SetZero();
}
// Compute effective mass.
float32 ruA = b2Cross(m_rA, m_uA);
float32 ruB = b2Cross(m_rB, m_uB);
float32 mA = m_invMassA + m_invIA * ruA * ruA;
float32 mB = m_invMassB + m_invIB * ruB * ruB;
m_mass = mA + m_ratio * m_ratio * mB;
if (m_mass > 0.0f)
{
m_mass = 1.0f / m_mass;
}
if (data.step.warmStarting)
{
// Scale impulses to support variable time steps.
m_impulse *= data.step.dtRatio;
// Warm starting.
b2Vec2 PA = -(m_impulse) * m_uA;
b2Vec2 PB = (-m_ratio * m_impulse) * m_uB;
vA += m_invMassA * PA;
wA += m_invIA * b2Cross(m_rA, PA);
vB += m_invMassB * PB;
wB += m_invIB * b2Cross(m_rB, PB);
}
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 b2PulleyJoint::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;
b2Vec2 vpA = vA + b2Cross(wA, m_rA);
b2Vec2 vpB = vB + b2Cross(wB, m_rB);
float32 Cdot = -b2Dot(m_uA, vpA) - m_ratio * b2Dot(m_uB, vpB);
float32 impulse = -m_mass * Cdot;
m_impulse += impulse;
b2Vec2 PA = -impulse * m_uA;
b2Vec2 PB = -m_ratio * impulse * m_uB;
vA += m_invMassA * PA;
wA += m_invIA * b2Cross(m_rA, PA);
vB += m_invMassB * PB;
wB += m_invIB * b2Cross(m_rB, PB);
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 b2PulleyJoint::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);
// Get the pulley axes.
b2Vec2 uA = cA + rA - m_groundAnchorA;
b2Vec2 uB = cB + rB - m_groundAnchorB;
float32 lengthA = uA.Length();
float32 lengthB = uB.Length();
if (lengthA > 10.0f * b2_linearSlop)
{
uA *= 1.0f / lengthA;
}
else
{
uA.SetZero();
}
if (lengthB > 10.0f * b2_linearSlop)
{
uB *= 1.0f / lengthB;
}
else
{
uB.SetZero();
}
// Compute effective mass.
float32 ruA = b2Cross(rA, uA);
float32 ruB = b2Cross(rB, uB);
float32 mA = m_invMassA + m_invIA * ruA * ruA;
float32 mB = m_invMassB + m_invIB * ruB * ruB;
float32 mass = mA + m_ratio * m_ratio * mB;
if (mass > 0.0f)
{
mass = 1.0f / mass;
}
float32 C = m_constant - lengthA - m_ratio * lengthB;
float32 linearError = b2Abs(C);
float32 impulse = -mass * C;
b2Vec2 PA = -impulse * uA;
b2Vec2 PB = -m_ratio * impulse * uB;
cA += m_invMassA * PA;
aA += m_invIA * b2Cross(rA, PA);
cB += m_invMassB * PB;
aB += m_invIB * b2Cross(rB, PB);
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 linearError < b2_linearSlop;
}
b2Vec2 b2PulleyJoint::GetAnchorA() const
{
return m_bodyA->GetWorldPoint(m_localAnchorA);
}
b2Vec2 b2PulleyJoint::GetAnchorB() const
{
return m_bodyB->GetWorldPoint(m_localAnchorB);
}
b2Vec2 b2PulleyJoint::GetReactionForce(float32 inv_dt) const
{
b2Vec2 P = m_impulse * m_uB;
return inv_dt * P;
}
float32 b2PulleyJoint::GetReactionTorque(float32 inv_dt) const
{
B2_NOT_USED(inv_dt);
return 0.0f;
}
b2Vec2 b2PulleyJoint::GetGroundAnchorA() const
{
return m_groundAnchorA;
}
b2Vec2 b2PulleyJoint::GetGroundAnchorB() const
{
return m_groundAnchorB;
}
float32 b2PulleyJoint::GetLengthA() const
{
b2Vec2 p = m_bodyA->GetWorldPoint(m_localAnchorA);
b2Vec2 s = m_groundAnchorA;
b2Vec2 d = p - s;
return d.Length();
}
float32 b2PulleyJoint::GetLengthB() const
{
b2Vec2 p = m_bodyB->GetWorldPoint(m_localAnchorB);
b2Vec2 s = m_groundAnchorB;
b2Vec2 d = p - s;
return d.Length();
}
float32 b2PulleyJoint::GetRatio() const
{
return m_ratio;
}
void b2PulleyJoint::Dump()
{
int32 indexA = m_bodyA->m_islandIndex;
int32 indexB = m_bodyB->m_islandIndex;
b2Log(" b2PulleyJointDef 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.groundAnchorA.Set(%.15lef, %.15lef);\n", m_groundAnchorA.x, m_groundAnchorA.y);
b2Log(" jd.groundAnchorB.Set(%.15lef, %.15lef);\n", m_groundAnchorB.x, m_groundAnchorB.y);
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.lengthA = %.15lef;\n", m_lengthA);
b2Log(" jd.lengthB = %.15lef;\n", m_lengthB);
b2Log(" jd.ratio = %.15lef;\n", m_ratio);
b2Log(" joints[%d] = m_world->CreateJoint(&jd);\n", m_index);
}