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Diffstat (limited to 'src/libjin/3rdparty/Box2D/Dynamics/Joints/b2MouseJoint.cpp')
| -rw-r--r-- | src/libjin/3rdparty/Box2D/Dynamics/Joints/b2MouseJoint.cpp | 222 |
1 files changed, 222 insertions, 0 deletions
diff --git a/src/libjin/3rdparty/Box2D/Dynamics/Joints/b2MouseJoint.cpp b/src/libjin/3rdparty/Box2D/Dynamics/Joints/b2MouseJoint.cpp new file mode 100644 index 0000000..637e4cd --- /dev/null +++ b/src/libjin/3rdparty/Box2D/Dynamics/Joints/b2MouseJoint.cpp @@ -0,0 +1,222 @@ +/* +* Copyright (c) 2006-2007 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 "Box2D/Dynamics/Joints/b2MouseJoint.h" +#include "Box2D/Dynamics/b2Body.h" +#include "Box2D/Dynamics/b2TimeStep.h" + +// p = attached point, m = mouse point +// C = p - m +// Cdot = v +// = v + cross(w, r) +// J = [I r_skew] +// Identity used: +// w k % (rx i + ry j) = w * (-ry i + rx j) + +b2MouseJoint::b2MouseJoint(const b2MouseJointDef* def) +: b2Joint(def) +{ + b2Assert(def->target.IsValid()); + b2Assert(b2IsValid(def->maxForce) && def->maxForce >= 0.0f); + b2Assert(b2IsValid(def->frequencyHz) && def->frequencyHz >= 0.0f); + b2Assert(b2IsValid(def->dampingRatio) && def->dampingRatio >= 0.0f); + + m_targetA = def->target; + m_localAnchorB = b2MulT(m_bodyB->GetTransform(), m_targetA); + + m_maxForce = def->maxForce; + m_impulse.SetZero(); + + m_frequencyHz = def->frequencyHz; + m_dampingRatio = def->dampingRatio; + + m_beta = 0.0f; + m_gamma = 0.0f; +} + +void b2MouseJoint::SetTarget(const b2Vec2& target) +{ + if (target != m_targetA) + { + m_bodyB->SetAwake(true); + m_targetA = target; + } +} + +const b2Vec2& b2MouseJoint::GetTarget() const +{ + return m_targetA; +} + +void b2MouseJoint::SetMaxForce(float32 force) +{ + m_maxForce = force; +} + +float32 b2MouseJoint::GetMaxForce() const +{ + return m_maxForce; +} + +void b2MouseJoint::SetFrequency(float32 hz) +{ + m_frequencyHz = hz; +} + +float32 b2MouseJoint::GetFrequency() const +{ + return m_frequencyHz; +} + +void b2MouseJoint::SetDampingRatio(float32 ratio) +{ + m_dampingRatio = ratio; +} + +float32 b2MouseJoint::GetDampingRatio() const +{ + return m_dampingRatio; +} + +void b2MouseJoint::InitVelocityConstraints(const b2SolverData& data) +{ + m_indexB = m_bodyB->m_islandIndex; + m_localCenterB = m_bodyB->m_sweep.localCenter; + m_invMassB = m_bodyB->m_invMass; + m_invIB = m_bodyB->m_invI; + + 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 qB(aB); + + float32 mass = m_bodyB->GetMass(); + + // Frequency + float32 omega = 2.0f * b2_pi * m_frequencyHz; + + // Damping coefficient + float32 d = 2.0f * mass * m_dampingRatio * omega; + + // Spring stiffness + float32 k = mass * (omega * omega); + + // magic formulas + // gamma has units of inverse mass. + // beta has units of inverse time. + float32 h = data.step.dt; + b2Assert(d + h * k > b2_epsilon); + m_gamma = h * (d + h * k); + if (m_gamma != 0.0f) + { + m_gamma = 1.0f / m_gamma; + } + m_beta = h * k * m_gamma; + + // Compute the effective mass matrix. + m_rB = b2Mul(qB, m_localAnchorB - m_localCenterB); + + // 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] + b2Mat22 K; + K.ex.x = m_invMassB + m_invIB * m_rB.y * m_rB.y + m_gamma; + K.ex.y = -m_invIB * m_rB.x * m_rB.y; + K.ey.x = K.ex.y; + K.ey.y = m_invMassB + m_invIB * m_rB.x * m_rB.x + m_gamma; + + m_mass = K.GetInverse(); + + m_C = cB + m_rB - m_targetA; + m_C *= m_beta; + + // Cheat with some damping + wB *= 0.98f; + + if (data.step.warmStarting) + { + m_impulse *= data.step.dtRatio; + vB += m_invMassB * m_impulse; + wB += m_invIB * b2Cross(m_rB, m_impulse); + } + else + { + m_impulse.SetZero(); + } + + data.velocities[m_indexB].v = vB; + data.velocities[m_indexB].w = wB; +} + +void b2MouseJoint::SolveVelocityConstraints(const b2SolverData& data) +{ + b2Vec2 vB = data.velocities[m_indexB].v; + float32 wB = data.velocities[m_indexB].w; + + // Cdot = v + cross(w, r) + b2Vec2 Cdot = vB + b2Cross(wB, m_rB); + b2Vec2 impulse = b2Mul(m_mass, -(Cdot + m_C + m_gamma * m_impulse)); + + b2Vec2 oldImpulse = m_impulse; + m_impulse += impulse; + float32 maxImpulse = data.step.dt * m_maxForce; + if (m_impulse.LengthSquared() > maxImpulse * maxImpulse) + { + m_impulse *= maxImpulse / m_impulse.Length(); + } + impulse = m_impulse - oldImpulse; + + vB += m_invMassB * impulse; + wB += m_invIB * b2Cross(m_rB, impulse); + + data.velocities[m_indexB].v = vB; + data.velocities[m_indexB].w = wB; +} + +bool b2MouseJoint::SolvePositionConstraints(const b2SolverData& data) +{ + B2_NOT_USED(data); + return true; +} + +b2Vec2 b2MouseJoint::GetAnchorA() const +{ + return m_targetA; +} + +b2Vec2 b2MouseJoint::GetAnchorB() const +{ + return m_bodyB->GetWorldPoint(m_localAnchorB); +} + +b2Vec2 b2MouseJoint::GetReactionForce(float32 inv_dt) const +{ + return inv_dt * m_impulse; +} + +float32 b2MouseJoint::GetReactionTorque(float32 inv_dt) const +{ + return inv_dt * 0.0f; +} + +void b2MouseJoint::ShiftOrigin(const b2Vec2& newOrigin) +{ + m_targetA -= newOrigin; +} |