cull.h

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/*! \file
  \brief  The disti::Culler class.  Implements view frustum culling.

  \par Copyright Information

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*/
#ifndef _CULL_H
#define _CULL_H

#include "util.h"
#include "vertex.h"

namespace disti
{
/** The Culler class.  Implements view frustum culling. */
class Culler
{
public:
    /** Return type for culling function */
    typedef enum
    {
        OUTSIDE_FRUSTUM,    /** The object was entirely outside of the viewing frustum */
        INTERSECTS_FRUSTUM, /** The object intersects the viewing frustum */
        INSIDE_FRUSTUM      /** The object was entirely inside the viewing frustum */
    } CullResultEnum;

    /** Definitions for the six frustum clipping planes */
    typedef enum
    {
        RIGHT_PLANE,
        LEFT_PLANE,
        BOTTOM_PLANE,
        TOP_PLANE,
        FAR_PLANE,
        NEAR_PLANE
    } ClippingPlanesEnum;

protected:
    bool _enabled; /** Whether or not culling is enabled */

    PlaneClass _planes[ 6 ]; /** Array of six clipping planes to define the frustum */

public:
    /** Culler constructor
      * \param enabled  Whether or not to actually to the culling test
      */
    GLS_EXPORT Culler( bool enabled = true );

    /** Reads the current OpenGL projection matrices and determines the six frustum planes
      * Note:  This assumes a perspective projection, but it will work with orthographic, 
      * though it could be optimized better if it was known that Ortho is being used.
      */
    GLS_EXPORT void ExtractFrustum( OpenGLMatrices& matrices );

    /** \return Whether the sphere is inside, outside or intersects the view frustum.
      */
    GLS_EXPORT CullResultEnum SphereInFrustum( const Vector& v, const float radius ) const;

    /** Slightly faster sphere culling because it doesn't test seperately 
      * for intersection and it ignores the Enabled() state.
      * \returns true if outside or intersecting, false if inside
      */
    inline bool SphereOutsideFrustum( const Vector& center, const float radius ) const
    {
        if( ( _planes[ 0 ].a * center.x + _planes[ 0 ].b * center.y + _planes[ 0 ].c * center.z + _planes[ 0 ].d ) <= -radius )
            return true;
        if( ( _planes[ 1 ].a * center.x + _planes[ 1 ].b * center.y + _planes[ 1 ].c * center.z + _planes[ 1 ].d ) <= -radius )
            return true;
        if( ( _planes[ 2 ].a * center.x + _planes[ 2 ].b * center.y + _planes[ 2 ].c * center.z + _planes[ 2 ].d ) <= -radius )
            return true;
        if( ( _planes[ 3 ].a * center.x + _planes[ 3 ].b * center.y + _planes[ 3 ].c * center.z + _planes[ 3 ].d ) <= -radius )
            return true;
        if( ( _planes[ 4 ].a * center.x + _planes[ 4 ].b * center.y + _planes[ 4 ].c * center.z + _planes[ 4 ].d ) <= -radius )
            return true;
        if( ( _planes[ 5 ].a * center.x + _planes[ 5 ].b * center.y + _planes[ 5 ].c * center.z + _planes[ 5 ].d ) <= -radius )
            return true;

        return false; // inside (or intersecting)
    }

    /** Accessor method to get whether or not culling is enabled
      * \return Whether or not culling is enabled
      */
    inline bool Enabled( void ) const { return _enabled; }

    /** Accessor method to set whether or not culling is enabled
      * Be carefull with this, because the Culler is usually passed
      * by reference.
      */
    inline void Enabled( bool newVal ) { _enabled = newVal; }

    /** \return A reference to the desired clipping plane for this view frustum */
    GLS_EXPORT const PlaneClass& Plane( const ClippingPlanesEnum& whichPlane ) const;
};

} // namespace disti

#endif