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Bullet Continuous Collision Detection and Physics Library,
Copyright (C) 2006, 2007 Sony Computer Entertainment Inc.
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In no event will the authors be held liable for any damages arising from the use of this software.
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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.
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#include "BulletDynamics/ConstraintSolver/btUniversalConstraint.h"
#include "BulletDynamics/Dynamics/btRigidBody.h"
#include "LinearMath/btTransformUtil.h"
#define UNIV_EPS btScalar(0.01f)
// constructor
// anchor, axis1 and axis2 are in world coordinate system
// axis1 must be orthogonal to axis2
btUniversalConstraint::btUniversalConstraint(btRigidBody& rbA, btRigidBody& rbB, btVector3& anchor, btVector3& axis1, btVector3& axis2)
: btGeneric6DofConstraint(rbA, rbB, btTransform::getIdentity(), btTransform::getIdentity(), true),
// build frame basis
// 6DOF constraint uses Euler angles and to define limits
// it is assumed that rotational order is :
// Z - first, allowed limits are (-PI,PI);
// new position of Y - second (allowed limits are (-PI/2 + epsilon, PI/2 - epsilon), where epsilon is a small positive number
// used to prevent constraint from instability on poles;
// new position of X, allowed limits are (-PI,PI);
// So to simulate ODE Universal joint we should use parent axis as Z, child axis as Y and limit all other DOFs
// Build the frame in world coordinate system first
btVector3 zAxis = axis1.normalize();
btVector3 yAxis = axis2.normalize();
btVector3 xAxis = yAxis.cross(zAxis); // we want right coordinate system
btTransform frameInW;
frameInW.getBasis().setValue( xAxis[0], yAxis[0], zAxis[0],
xAxis[1], yAxis[1], zAxis[1],
xAxis[2], yAxis[2], zAxis[2]);
// now get constraint frame in local coordinate systems
m_frameInA = rbA.getCenterOfMassTransform().inverse() * frameInW;
m_frameInB = rbB.getCenterOfMassTransform().inverse() * frameInW;
// sei limits
setLinearLowerLimit(btVector3(0., 0., 0.));
setLinearUpperLimit(btVector3(0., 0., 0.));
setAngularLowerLimit(btVector3(0.f, -SIMD_HALF_PI + UNIV_EPS, -SIMD_PI + UNIV_EPS));
setAngularUpperLimit(btVector3(0.f, SIMD_HALF_PI - UNIV_EPS, SIMD_PI - UNIV_EPS));