GuIntersectionRayCapsule.h

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#ifndef GU_INTERSECTION_RAY_CAPSULE_H
#define GU_INTERSECTION_RAY_CAPSULE_H
 
#include "GuCapsule.h"
#include "GuDistancePointSegment.h"
#include "GuIntersectionRay.h"
 
namespace physx
{
namespace Gu
{
    PxU32 intersectRayCapsuleInternal(const PxVec3& origin, const PxVec3& dir, const PxVec3& p0, const PxVec3& p1, float radius, PxReal s[2]);
 
    PX_FORCE_INLINE bool intersectRayCapsule(const PxVec3& origin, const PxVec3& dir, const PxVec3& p0, const PxVec3& p1, float radius, PxReal& t)
    {
        // PT: move ray origin close to capsule, to solve accuracy issues.
        // We compute the distance D between the ray origin and the capsule's segment.
        // Then E = D - radius = distance between the ray origin and the capsule.
        // We can move the origin freely along 'dir' up to E units before touching the capsule.
        PxReal l = distancePointSegmentSquaredInternal(p0, p1 - p0, origin);
        l = PxSqrt(l) - radius;
 
        // PT: if this becomes negative or null, the ray starts inside the capsule and we can early exit
        if(l<=0.0f)
        {
            t = 0.0f;
            return true;
        }
 
        // PT: we remove an arbitrary GU_RAY_SURFACE_OFFSET units to E, to make sure we don't go close to the surface.
        // If we're moving in the direction of the capsule, the origin is now about GU_RAY_SURFACE_OFFSET units from it.
        // If we're moving away from the capsule, the ray won't hit the capsule anyway.
        // If l is smaller than GU_RAY_SURFACE_OFFSET we're close enough, accuracy is good, there is nothing to do.
        if(l>GU_RAY_SURFACE_OFFSET)
            l -= GU_RAY_SURFACE_OFFSET;
        else
            l = 0.0f;
 
        // PT: move origin closer to capsule and do the raycast
        PxReal s[2];
        const PxU32 nbHits = Gu::intersectRayCapsuleInternal(origin + l*dir, dir, p0, p1, radius, s);
        if(!nbHits)
            return false;
 
        // PT: keep closest hit only
        if(nbHits == 1)
            t = s[0];
        else
            t = (s[0] < s[1]) ? s[0] : s[1];
 
        // PT: fix distance (smaller than expected after moving ray close to capsule)
        t += l;
        return true;
    }
 
    PX_FORCE_INLINE bool intersectRayCapsule(const PxVec3& origin, const PxVec3& dir, const Gu::Capsule& capsule, PxReal& t)
    {
        return Gu::intersectRayCapsule(origin, dir, capsule.p0, capsule.p1, capsule.radius, t);
    }
}
}
 
#endif