ray.hpp

/*
 * Copyright (c) 2006-2016, 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/>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * 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
 * written permission.
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * 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__RAY__HPP__
#define __VMML__RAY__HPP__

#include <vmmlib/vector.hpp>

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

    Ray(const vec3& origin, const vec3& direction)
        : _origin(origin)
        , _direction(vmml::normalize(direction))
    {
    }
    ~Ray() {}
    T test(const vec4& sphere) const;

private:
    const vec3 _origin;
    const vec3 _direction;
};

template <typename T>
T Ray<T>::test(const vec4& sphere) 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 -1.f;

    const T sqCenterToProj = sqDistance - vecProjection * vecProjection;

    if (sqCenterToProj > sqRadius)
        return -1.f;

    const T distSurface = sqrt(sqRadius - sqCenterToProj);

    if (sqDistance > sqRadius)
        return vecProjection - distSurface;

    return vecProjection + distSurface;
}

} // namespace vmml

#endif