1 files changed, 421 insertions, 0 deletions
diff --git a/Client/ThirdParty/Box2D/src/dynamics/b2_distance_joint.cpp b/Client/ThirdParty/Box2D/src/dynamics/b2_distance_joint.cpp
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+++ b/Client/ThirdParty/Box2D/src/dynamics/b2_distance_joint.cpp
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+// MIT License
+
+// Copyright (c) 2019 Erin Catto
+
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#include "box2d/b2_body.h"
+#include "box2d/b2_draw.h"
+#include "box2d/b2_distance_joint.h"
+#include "box2d/b2_time_step.h"
+
+// 1-D constrained system
+// m (v2 - v1) = lambda
+// v2 + (beta/h) * x1 + gamma * lambda = 0, gamma has units of inverse mass.
+// x2 = x1 + h * v2
+
+// 1-D mass-damper-spring system
+// m (v2 - v1) + h * d * v2 + h * k * 
+
+// C = norm(p2 - p1) - L
+// u = (p2 - p1) / norm(p2 - p1)
+// Cdot = dot(u, v2 + cross(w2, r2) - v1 - cross(w1, r1))
+// J = [-u -cross(r1, u) u cross(r2, u)]
+// K = J * invM * JT
+//   = invMass1 + invI1 * cross(r1, u)^2 + invMass2 + invI2 * cross(r2, u)^2
+
+
+void b2DistanceJointDef::Initialize(b2Body* b1, b2Body* b2,
+									const b2Vec2& anchor1, const b2Vec2& anchor2)
+{
+	bodyA = b1;
+	bodyB = b2;
+	localAnchorA = bodyA->GetLocalPoint(anchor1);
+	localAnchorB = bodyB->GetLocalPoint(anchor2);
+	b2Vec2 d = anchor2 - anchor1;
+	length = b2Max(d.Length(), b2_linearSlop);
+	minLength = length;
+	maxLength = length;
+}
+
+b2DistanceJoint::b2DistanceJoint(const b2DistanceJointDef* def)
+: b2Joint(def)
+{
+	m_localAnchorA = def->localAnchorA;
+	m_localAnchorB = def->localAnchorB;
+	m_length = b2Max(def->length, b2_linearSlop);
+	m_minLength = b2Max(def->minLength, b2_linearSlop);
+	m_maxLength = b2Max(def->maxLength, m_minLength);
+	m_stiffness = def->stiffness;
+	m_damping = def->damping;
+
+	m_gamma = 0.0f;
+	m_bias = 0.0f;
+	m_impulse = 0.0f;
+	m_lowerImpulse = 0.0f;
+	m_upperImpulse = 0.0f;
+	m_currentLength = 0.0f;
+}
+
+void b2DistanceJoint::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;
+	float aA = data.positions[m_indexA].a;
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float wA = data.velocities[m_indexA].w;
+
+	b2Vec2 cB = data.positions[m_indexB].c;
+	float aB = data.positions[m_indexB].a;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float 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;
+
+	// Handle singularity.
+	m_currentLength = m_u.Length();
+	if (m_currentLength > b2_linearSlop)
+	{
+		m_u *= 1.0f / m_currentLength;
+	}
+	else
+	{
+		m_u.Set(0.0f, 0.0f);
+		m_mass = 0.0f;
+		m_impulse = 0.0f;
+		m_lowerImpulse = 0.0f;
+		m_upperImpulse = 0.0f;
+	}
+
+	float crAu = b2Cross(m_rA, m_u);
+	float crBu = b2Cross(m_rB, m_u);
+	float invMass = m_invMassA + m_invIA * crAu * crAu + m_invMassB + m_invIB * crBu * crBu;
+	m_mass = invMass != 0.0f ? 1.0f / invMass : 0.0f;
+
+	if (m_stiffness > 0.0f && m_minLength < m_maxLength)
+	{
+		// soft
+		float C = m_currentLength - m_length;
+
+		float d = m_damping;
+		float k = m_stiffness;
+
+		// magic formulas
+		float h = data.step.dt;
+
+		// gamma = 1 / (h * (d + h * k))
+		// the extra factor of h in the denominator is since the lambda is an impulse, not a force
+		m_gamma = h * (d + h * k);
+		m_gamma = m_gamma != 0.0f ? 1.0f / m_gamma : 0.0f;
+		m_bias = C * h * k * m_gamma;
+
+		invMass += m_gamma;
+		m_softMass = invMass != 0.0f ? 1.0f / invMass : 0.0f;
+	}
+	else
+	{
+		// rigid
+		m_gamma = 0.0f;
+		m_bias = 0.0f;
+		m_softMass = m_mass;
+	}
+
+	if (data.step.warmStarting)
+	{
+		// Scale the impulse to support a variable time step.
+		m_impulse *= data.step.dtRatio;
+		m_lowerImpulse *= data.step.dtRatio;
+		m_upperImpulse *= data.step.dtRatio;
+
+		b2Vec2 P = (m_impulse + m_lowerImpulse - m_upperImpulse) * 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 b2DistanceJoint::SolveVelocityConstraints(const b2SolverData& data)
+{
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float wA = data.velocities[m_indexA].w;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float wB = data.velocities[m_indexB].w;
+
+	if (m_minLength < m_maxLength)
+	{
+		if (m_stiffness > 0.0f)
+		{
+			// Cdot = dot(u, v + cross(w, r))
+			b2Vec2 vpA = vA + b2Cross(wA, m_rA);
+			b2Vec2 vpB = vB + b2Cross(wB, m_rB);
+			float Cdot = b2Dot(m_u, vpB - vpA);
+
+			float impulse = -m_softMass * (Cdot + m_bias + m_gamma * m_impulse);
+			m_impulse += impulse;
+
+			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);
+		}
+
+		// lower
+		{
+			float C = m_currentLength - m_minLength;
+			float bias = b2Max(0.0f, C) * data.step.inv_dt;
+
+			b2Vec2 vpA = vA + b2Cross(wA, m_rA);
+			b2Vec2 vpB = vB + b2Cross(wB, m_rB);
+			float Cdot = b2Dot(m_u, vpB - vpA);
+
+			float impulse = -m_mass * (Cdot + bias);
+			float oldImpulse = m_lowerImpulse;
+			m_lowerImpulse = b2Max(0.0f, m_lowerImpulse + impulse);
+			impulse = m_lowerImpulse - 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);
+		}
+
+		// upper
+		{
+			float C = m_maxLength - m_currentLength;
+			float bias = b2Max(0.0f, C) * data.step.inv_dt;
+
+			b2Vec2 vpA = vA + b2Cross(wA, m_rA);
+			b2Vec2 vpB = vB + b2Cross(wB, m_rB);
+			float Cdot = b2Dot(m_u, vpA - vpB);
+
+			float impulse = -m_mass * (Cdot + bias);
+			float oldImpulse = m_upperImpulse;
+			m_upperImpulse = b2Max(0.0f, m_upperImpulse + impulse);
+			impulse = m_upperImpulse - 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);
+		}
+	}
+	else
+	{
+		// Equal limits
+
+		// Cdot = dot(u, v + cross(w, r))
+		b2Vec2 vpA = vA + b2Cross(wA, m_rA);
+		b2Vec2 vpB = vB + b2Cross(wB, m_rB);
+		float Cdot = b2Dot(m_u, vpB - vpA);
+
+		float impulse = -m_mass * Cdot;
+		m_impulse += impulse;
+
+		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 b2DistanceJoint::SolvePositionConstraints(const b2SolverData& data)
+{
+	b2Vec2 cA = data.positions[m_indexA].c;
+	float aA = data.positions[m_indexA].a;
+	b2Vec2 cB = data.positions[m_indexB].c;
+	float 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;
+
+	float length = u.Normalize();
+	float C;
+	if (m_minLength == m_maxLength)
+	{
+		C = length - m_minLength;
+	}
+	else if (length < m_minLength)
+	{
+		C = length - m_minLength;
+	}
+	else if (m_maxLength < length)
+	{
+		C = length - m_maxLength;
+	}
+	else
+	{
+		return true;
+	}
+
+	float 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 b2Abs(C) < b2_linearSlop;
+}
+
+b2Vec2 b2DistanceJoint::GetAnchorA() const
+{
+	return m_bodyA->GetWorldPoint(m_localAnchorA);
+}
+
+b2Vec2 b2DistanceJoint::GetAnchorB() const
+{
+	return m_bodyB->GetWorldPoint(m_localAnchorB);
+}
+
+b2Vec2 b2DistanceJoint::GetReactionForce(float inv_dt) const
+{
+	b2Vec2 F = inv_dt * (m_impulse + m_lowerImpulse - m_upperImpulse) * m_u;
+	return F;
+}
+
+float b2DistanceJoint::GetReactionTorque(float inv_dt) const
+{
+	B2_NOT_USED(inv_dt);
+	return 0.0f;
+}
+
+float b2DistanceJoint::SetLength(float length)
+{
+	m_impulse = 0.0f;
+	m_length = b2Max(b2_linearSlop, length);
+	return m_length;
+}
+
+float b2DistanceJoint::SetMinLength(float minLength)
+{
+	m_lowerImpulse = 0.0f;
+	m_minLength = b2Clamp(minLength, b2_linearSlop, m_maxLength);
+	return m_minLength;
+}
+
+float b2DistanceJoint::SetMaxLength(float maxLength)
+{
+	m_upperImpulse = 0.0f;
+	m_maxLength = b2Max(maxLength, m_minLength);
+	return m_maxLength;
+}
+
+float b2DistanceJoint::GetCurrentLength() const
+{
+	b2Vec2 pA = m_bodyA->GetWorldPoint(m_localAnchorA);
+	b2Vec2 pB = m_bodyB->GetWorldPoint(m_localAnchorB);
+	b2Vec2 d = pB - pA;
+	float length = d.Length();
+	return length;
+}
+
+void b2DistanceJoint::Dump()
+{
+	int32 indexA = m_bodyA->m_islandIndex;
+	int32 indexB = m_bodyB->m_islandIndex;
+
+	b2Dump("  b2DistanceJointDef jd;\n");
+	b2Dump("  jd.bodyA = bodies[%d];\n", indexA);
+	b2Dump("  jd.bodyB = bodies[%d];\n", indexB);
+	b2Dump("  jd.collideConnected = bool(%d);\n", m_collideConnected);
+	b2Dump("  jd.localAnchorA.Set(%.9g, %.9g);\n", m_localAnchorA.x, m_localAnchorA.y);
+	b2Dump("  jd.localAnchorB.Set(%.9g, %.9g);\n", m_localAnchorB.x, m_localAnchorB.y);
+	b2Dump("  jd.length = %.9g;\n", m_length);
+	b2Dump("  jd.minLength = %.9g;\n", m_minLength);
+	b2Dump("  jd.maxLength = %.9g;\n", m_maxLength);
+	b2Dump("  jd.stiffness = %.9g;\n", m_stiffness);
+	b2Dump("  jd.damping = %.9g;\n", m_damping);
+	b2Dump("  joints[%d] = m_world->CreateJoint(&jd);\n", m_index);
+}
+
+void b2DistanceJoint::Draw(b2Draw* draw) const
+{
+	const b2Transform& xfA = m_bodyA->GetTransform();
+	const b2Transform& xfB = m_bodyB->GetTransform();
+	b2Vec2 pA = b2Mul(xfA, m_localAnchorA);
+	b2Vec2 pB = b2Mul(xfB, m_localAnchorB);
+
+	b2Vec2 axis = pB - pA;
+	float length = axis.Normalize();
+
+	b2Color c1(0.7f, 0.7f, 0.7f);
+	b2Color c2(0.3f, 0.9f, 0.3f);
+	b2Color c3(0.9f, 0.3f, 0.3f);
+	b2Color c4(0.4f, 0.4f, 0.4f);
+
+	draw->DrawSegment(pA, pB, c4);
+	
+	b2Vec2 pRest = pA + m_length * axis;
+	draw->DrawPoint(pRest, 8.0f, c1);
+
+	if (m_minLength != m_maxLength)
+	{
+		if (m_minLength > b2_linearSlop)
+		{
+			b2Vec2 pMin = pA + m_minLength * axis;
+			draw->DrawPoint(pMin, 4.0f, c2);
+		}
+
+		if (m_maxLength < FLT_MAX)
+		{
+			b2Vec2 pMax = pA + m_maxLength * axis;
+			draw->DrawPoint(pMax, 4.0f, c3);
+		}
+	}
+}