btContinuousConvexCollision.cpp

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/*
Bullet Continuous Collision Detection and Physics Library
Copyright (c) 2003-2006 Erwin Coumans  http://continuousphysics.com/Bullet/

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 "btContinuousConvexCollision.h"
#include "BulletCollision/CollisionShapes/btConvexShape.h"
#include "BulletCollision/NarrowPhaseCollision/btSimplexSolverInterface.h"
#include "LinearMath/btTransformUtil.h"
#include "BulletCollision/CollisionShapes/btSphereShape.h"

#include "btGjkPairDetector.h"
#include "btPointCollector.h"



btContinuousConvexCollision::btContinuousConvexCollision ( const btConvexShape* convexA,const btConvexShape*    convexB,btSimplexSolverInterface* simplexSolver, btConvexPenetrationDepthSolver* penetrationDepthSolver)
:m_simplexSolver(simplexSolver),
m_penetrationDepthSolver(penetrationDepthSolver),
m_convexA(convexA),m_convexB(convexB)
{
}

#define MAX_ITERATIONS 64

bool    btContinuousConvexCollision::calcTimeOfImpact(
                const btTransform& fromA,
                const btTransform& toA,
                const btTransform& fromB,
                const btTransform& toB,
                CastResult& result)
{

    m_simplexSolver->reset();

    btVector3 linVelA,angVelA,linVelB,angVelB;
    btTransformUtil::calculateVelocity(fromA,toA,btScalar(1.),linVelA,angVelA);
    btTransformUtil::calculateVelocity(fromB,toB,btScalar(1.),linVelB,angVelB);


    btScalar boundingRadiusA = m_convexA->getAngularMotionDisc();
    btScalar boundingRadiusB = m_convexB->getAngularMotionDisc();

    btScalar maxAngularProjectedVelocity = angVelA.length() * boundingRadiusA + angVelB.length() * boundingRadiusB;
    btVector3 relLinVel = (linVelB-linVelA);

    btScalar relLinVelocLength = (linVelB-linVelA).length();
    
    if ((relLinVelocLength+maxAngularProjectedVelocity) == 0.f)
        return false;


    btScalar radius = btScalar(0.001);

    btScalar lambda = btScalar(0.);
    btVector3 v(1,0,0);

    int maxIter = MAX_ITERATIONS;

    btVector3 n;
    n.setValue(btScalar(0.),btScalar(0.),btScalar(0.));
    bool hasResult = false;
    btVector3 c;

    btScalar lastLambda = lambda;
    //btScalar epsilon = btScalar(0.001);

    int numIter = 0;
    //first solution, using GJK


    btTransform identityTrans;
    identityTrans.setIdentity();

    btSphereShape   raySphere(btScalar(0.0));
    raySphere.setMargin(btScalar(0.));


//  result.drawCoordSystem(sphereTr);

    btPointCollector    pointCollector1;

    {
        
        btGjkPairDetector gjk(m_convexA,m_convexB,m_convexA->getShapeType(),m_convexB->getShapeType(),m_convexA->getMargin(),m_convexB->getMargin(),m_simplexSolver,m_penetrationDepthSolver);      
        btGjkPairDetector::ClosestPointInput input;
    
        //we don't use margins during CCD
    //  gjk.setIgnoreMargin(true);

        input.m_transformA = fromA;
        input.m_transformB = fromB;
        gjk.getClosestPoints(input,pointCollector1,0);

        hasResult = pointCollector1.m_hasResult;
        c = pointCollector1.m_pointInWorld;
    }

    if (hasResult)
    {
        btScalar dist;
        dist = pointCollector1.m_distance;
        n = pointCollector1.m_normalOnBInWorld;

        btScalar projectedLinearVelocity = relLinVel.dot(n);
        
        //not close enough
        while (dist > radius)
        {
            if (result.m_debugDrawer)
            {
                result.m_debugDrawer->drawSphere(c,0.2f,btVector3(1,1,1));
            }
            numIter++;
            if (numIter > maxIter)
            {
                return false; //todo: report a failure
            }
            btScalar dLambda = btScalar(0.);

            projectedLinearVelocity = relLinVel.dot(n);

            //calculate safe moving fraction from distance / (linear+rotational velocity)
            
            //btScalar clippedDist  = GEN_min(angularConservativeRadius,dist);
            //btScalar clippedDist  = dist;
            
            //don't report time of impact for motion away from the contact normal (or causes minor penetration)
            if ((projectedLinearVelocity+ maxAngularProjectedVelocity)<=SIMD_EPSILON)
                return false;
            
            dLambda = dist / (projectedLinearVelocity+ maxAngularProjectedVelocity);

            
            
            lambda = lambda + dLambda;

            if (lambda > btScalar(1.))
                return false;

            if (lambda < btScalar(0.))
                return false;


            //todo: next check with relative epsilon
            if (lambda <= lastLambda)
            {
                return false;
                //n.setValue(0,0,0);
                break;
            }
            lastLambda = lambda;

            

            //interpolate to next lambda
            btTransform interpolatedTransA,interpolatedTransB,relativeTrans;

            btTransformUtil::integrateTransform(fromA,linVelA,angVelA,lambda,interpolatedTransA);
            btTransformUtil::integrateTransform(fromB,linVelB,angVelB,lambda,interpolatedTransB);
            relativeTrans = interpolatedTransB.inverseTimes(interpolatedTransA);

            if (result.m_debugDrawer)
            {
                result.m_debugDrawer->drawSphere(interpolatedTransA.getOrigin(),0.2f,btVector3(1,0,0));
            }

            result.DebugDraw( lambda );

            btPointCollector    pointCollector;
            btGjkPairDetector gjk(m_convexA,m_convexB,m_simplexSolver,m_penetrationDepthSolver);
            btGjkPairDetector::ClosestPointInput input;
            input.m_transformA = interpolatedTransA;
            input.m_transformB = interpolatedTransB;
            gjk.getClosestPoints(input,pointCollector,0);
            if (pointCollector.m_hasResult)
            {
                if (pointCollector.m_distance < btScalar(0.))
                {
                    //degenerate ?!
                    result.m_fraction = lastLambda;
                    n = pointCollector.m_normalOnBInWorld;
                    result.m_normal=n;//.setValue(1,1,1);// = n;
                    result.m_hitPoint = pointCollector.m_pointInWorld;
                    return true;
                }
                c = pointCollector.m_pointInWorld;      
                n = pointCollector.m_normalOnBInWorld;
                dist = pointCollector.m_distance;
            } else
            {
                //??
                return false;
            }
            

        }
    
        if ((projectedLinearVelocity+ maxAngularProjectedVelocity)<=result.m_allowedPenetration)//SIMD_EPSILON)
            return false;
            
        result.m_fraction = lambda;
        result.m_normal = n;
        result.m_hitPoint = c;
        return true;
    }

    return false;

/*
//todo:
    //if movement away from normal, discard result
    btVector3 move = transBLocalTo.getOrigin() - transBLocalFrom.getOrigin();
    if (result.m_fraction < btScalar(1.))
    {
        if (move.dot(result.m_normal) <= btScalar(0.))
        {
        }
    }
*/

}