intersection.hpp

/*
 * Copyright (c) 2006-2014, Visualization and Multimedia Lab,
 *                          University of Zurich <http://vmml.ifi.uzh.ch>,
 *                          Eyescale Software GmbH,
 *                          Blue Brain Project, EPFL
 *
 * This file is part of VMMLib <https://github.com/VMML/vmmlib/>
 *
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 * modification, are permitted provided that the following conditions are met:
 *
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 * list of conditions and the following disclaimer.  Redistributions in binary
 * form must reproduce the above copyright notice, this list of conditions and
 * the following disclaimer in the documentation and/or other materials provided
 * with the distribution.  Neither the name of the Visualization and Multimedia
 * Lab, University of Zurich nor the names of its contributors may be used to
 * endorse or promote products derived from this software without specific prior
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 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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/* @author Jafet Villafranca
 *
 * Implements ray-object intersection, storing the ray parameters as attributes
 * and implementing intersection tests against different types of objects
 * (e.g. sphere)
 */

#ifndef __VMML__INTERSECTION__HPP__
#define __VMML__INTERSECTION__HPP__

#include <vmmlib/vector.hpp>

namespace vmml
{
template< typename T > class intersection
{
public:
    typedef vector< 3, T >    vec3;
    typedef vector< 4, T >    vec4;

    intersection( const vec3& origin, const vec3& direction )
        : _origin ( origin )
        , _direction ( vmml::normalize( direction ))
    {}
    ~intersection() {}

    bool test_sphere( const vec4& sphere, T& t ) const;

private:
    const vec3 _origin;
    const vec3 _direction;

}; // class intersection


template< typename T >
bool
intersection< T >::test_sphere( const vec4& sphere, T& t ) const
{
    const vec3 center = vec3(sphere.x(), sphere.y(), sphere.z());
    const T radius = sphere.w();

    const vec3 centerVec = center - _origin;
    const T vecProjection = centerVec.dot(_direction);

    const T sqDistance = centerVec.squared_length();
    const T sqRadius = radius * radius;

    if( vecProjection < 0 && sqDistance > sqRadius )
        return false;

    const T sqCenterToProj = sqDistance - vecProjection * vecProjection;

    if( sqCenterToProj > sqRadius )
        return false;

    const T distSurface = sqrt( sqRadius - sqCenterToProj );

    if(sqDistance > sqRadius)
        t = vecProjection - distSurface;
    else
        t = vecProjection + distSurface;

    return true;
}


} // namespace vmml

#endif