reactphysics3d/src/collision/narrowphase/SphereVsSphereAlgorithm.cpp

/********************************************************************************
* ReactPhysics3D physics library, http://www.reactphysics3d.com                 *
* Copyright (c) 2010-2016 Daniel Chappuis                                       *
*********************************************************************************
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* This software is provided 'as-is', without any express or implied warranty.   *
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// Libraries
#include "SphereVsSphereAlgorithm.h"
#include "collision/shapes/SphereShape.h"

// We want to use the ReactPhysics3D namespace
using namespace reactphysics3d;  

bool SphereVsSphereAlgorithm::testCollision(const NarrowPhaseInfo* narrowPhaseInfo,
                                            ContactPointInfo& contactPointInfo) {
    
    // Get the sphere collision shapes
    const SphereShape* sphereShape1 = static_cast<const SphereShape*>(narrowPhaseInfo->collisionShape1);
    const SphereShape* sphereShape2 = static_cast<const SphereShape*>(narrowPhaseInfo->collisionShape2);

    // Get the local-space to world-space transforms
    const Transform& transform1 = narrowPhaseInfo->shape1ToWorldTransform;
    const Transform& transform2 = narrowPhaseInfo->shape2ToWorldTransform;

    // Compute the distance between the centers
    Vector3 vectorBetweenCenters = transform2.getPosition() - transform1.getPosition();
    decimal squaredDistanceBetweenCenters = vectorBetweenCenters.lengthSquare();

    // Compute the sum of the radius
    decimal sumRadius = sphereShape1->getRadius() + sphereShape2->getRadius();
    
    // If the sphere collision shapes intersect
    if (squaredDistanceBetweenCenters <= sumRadius * sumRadius) {
        Vector3 centerSphere2InBody1LocalSpace = transform1.getInverse() * transform2.getPosition();
        Vector3 centerSphere1InBody2LocalSpace = transform2.getInverse() * transform1.getPosition();
        Vector3 intersectionOnBody1 = sphereShape1->getRadius() *
                                      centerSphere2InBody1LocalSpace.getUnit();
        Vector3 intersectionOnBody2 = sphereShape2->getRadius() *
                                      centerSphere1InBody2LocalSpace.getUnit();
        decimal penetrationDepth = sumRadius - std::sqrt(squaredDistanceBetweenCenters);
        
        // Create the contact info object
        contactPointInfo.init(vectorBetweenCenters.getUnit(), penetrationDepth,
                              intersectionOnBody1, intersectionOnBody2);

        return true;
    }

    return false;
}