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AI_SDB_PlaneClipper.h

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#ifndef AI_SDB_PLANECLIPPER_H
#define AI_SDB_PLANECLIPPER_H

#include "../math/AI_Plane.h"
#include "../math/AI_Sphere.h"
#include "../math/AI_BBox.h"

// this is currently limited to leave some bitflags available in the AI_SDB_VisitorFlags struct
// NOTE: keep this up-to-date, so visitors can add flags on the higher bits
#define AI_SDB_PLANECLIPPER_MAXPLANES 16

class AI_SDB_PlaneClipper {
public:
    AI_SDB_PlaneClipper();
    AI_SDB_PlaneClipper(const AI_SDB_PlaneClipper &copyme);
    AI_SDB_PlaneClipper(const AI_Plane *clipplanes, int numplanes);

    AI_SDB_VisitorFlags TestBBox(const AI_BBox &boxtest, AI_SDB_VisitorFlags in);

    AI_SDB_VisitorFlags TestSphere(const AI_Sphere &spheretest, AI_SDB_VisitorFlags in);

    AI_SDB_VisitorFlags TestPoint(const AI_Vector3 &pointtest, AI_SDB_VisitorFlags in);

protected:
    AI_Plane m_planes[AI_SDB_PLANECLIPPER_MAXPLANES];
    int m_numplanes;
};

inline
AI_SDB_PlaneClipper::AI_SDB_PlaneClipper()
{
}

inline
AI_SDB_PlaneClipper::AI_SDB_PlaneClipper(const AI_SDB_PlaneClipper &copyme)
{
    m_numplanes = copyme.m_numplanes;

    for (int i=0; i < copyme.m_numplanes; i++)
        m_planes[i] = copyme.m_planes[i];
}


inline
AI_SDB_PlaneClipper::AI_SDB_PlaneClipper(const AI_Plane *clipplanes, int numplanes)
: m_numplanes(numplanes)
{
    // initialize from user-supplied planes
    for (int i=0; i < numplanes; i++)
    {
        m_planes[i] = clipplanes[i];
    }
}

inline
AI_SDB_VisitorFlags AI_SDB_PlaneClipper::TestBBox(const AI_BBox &boxtest, AI_SDB_VisitorFlags in)
{
    // Returns a visibility code indicating the culling status of the
    // given axis-aligned box.  The result_info passed in should indicate
    // which planes might cull the box, by setting the corresponding
    // bit in in.active_planes.
    AI_Vector3 center = boxtest.center();
    AI_Vector3 extent = boxtest.extents();

    // Check the box against each active frustum AI_Plane.
    int bit = 1;
    int allplanebits( (1<<m_numplanes) - 1 );
    for (int i = 0; i < m_numplanes; i++, bit <<= 1)
    {
        // do the test only if the specified AI_Plane is active
        if ((bit & in.m_activeflags) != 0)
        {
            const AI_Plane&    p       = m_planes[i];
            const AI_Vector3 normal    = p.normal();
            
            // Check box against this AI_Plane.
            float   d = normal % center + p.d; //Calculate closest distance from center point to AI_Plane.
            float   extent_toward_plane = ai_abs(extent.x * normal.x)
                + ai_abs(extent.y * normal.y)
                + ai_abs(extent.z * normal.z);
            if (d < 0)
            {  
                if (-d > extent_toward_plane)
                {
                    // Box is definitively on the negative side of the AI_Plane, so it's culled
                    return AI_SDB_VisitorFlags(false,true);
                } // else this AI_Plane is ambiguous so leave it active.
            } else {
                if (d > extent_toward_plane)
                {
                    // Box is accepted by this AI_Plane, so
                    // deactivate it, since neither this
                    // box or any contained part of it can
                    // ever be culled by this AI_Plane.
                    in.m_activeflags &= ~bit;
                    if ( (in.m_activeflags & allplanebits) == 0)
                    {
                        // This box is definitively inside all the culling
                        // planes, so there's no need to continue.
                        return AI_SDB_VisitorFlags(true,false);
                    }
                } // else this AI_Plane is ambigious so leave it active.
            }
        }
    }

    return in;  // Box not definitively culled.  Return updated active AI_Plane flags.
}

inline
AI_SDB_VisitorFlags AI_SDB_PlaneClipper::TestSphere(const AI_Sphere &spheretest, AI_SDB_VisitorFlags ri)
{
    // build a bbox from the AI_Sphere and test that
    AI_BBox mybbox(spheretest.p, AI_Vector3(spheretest.r, spheretest.r, spheretest.r));
    return TestBBox(mybbox, ri);
}

inline
AI_SDB_VisitorFlags AI_SDB_PlaneClipper::TestPoint(const AI_Vector3 &pointtest, AI_SDB_VisitorFlags ri)
{
    // build a bbox from the point and test that
    AI_BBox mybbox(pointtest, AI_Vector3(0,0,0));
    return TestBBox(mybbox, ri);
}

#endif

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