plane.cpp

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/*
    toxic - A Global Illumination Renderer
    Copyright (C) 2003-2004 Francois Beaune
    Contact: http://toxicengine.sourceforge.net/

    This file is part of toxic.

    toxic is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    toxic is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with toxic; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

#include "plane.h"  // include first
#include "common/math/real.h"
#include "common/math/vector3.h"
#include "context.h"
#include "hit.h"
#include "ray.h"
#include "statistics.h"

#include <cassert>

using namespace sheep;
using namespace toxic;

Plane::Plane(const Matrix4 &m,
             const ISurfaceShader *surface_shader,
             IntersectionMask intersection_mask /*= INTERSECT_ALL_RAYS*/) :
    IObject(m, surface_shader, intersection_mask)
{
}

bool Plane::Intersect(const Context &context,
                      const Ray &ray,   //!< 'ray' is expressed in world space.
                      Hit *hit /*= 0*/) const
{
    // Test whether this object intersects with this type of ray.
    if(!(m_intersection_mask & ray.GetType()))
        return false;

    // Note: rescaling of the intersection abscissa has been optimized out from this code.

    ++context.m_statistics->m_tested_intersections;

    const Real oy =
        m_inv_m[4] * ray.m_origin.m_x +
        m_inv_m[5] * ray.m_origin.m_y +
        m_inv_m[6] * ray.m_origin.m_z +
        m_inv_m[7];

    const Real dy =
        m_inv_m[4] * ray.m_direction.m_x +
        m_inv_m[5] * ray.m_direction.m_y +
        m_inv_m[6] * ray.m_direction.m_z;

    if(dy == 0.0) {
        // The ray is parallel to the plane.

        if(oy != 0.0) {
            // The ray is parallel to the plane but does not lie in the plane.
            return false;
        }

        // The ray lies in the plane: report an intersection at abscissa 0.
        ++context.m_statistics->m_intersections_found;

        if(hit) {
            hit->m_object = this;
            hit->m_abscissa = 0.0;  // world space
            hit->m_geometric_normal = Vector3(0.0, 1.0, 0.0);   // object space -- normal is somewhat arbitrary in this case
            hit->m_shading_normal = hit->m_geometric_normal;    // object space
        }

        return true;
    } else {
        // The ray is not parallel to the plane.

        const Real t = - oy / dy;

        if(t < 0.0)
            return false;   // the intersection point is not on the ray

        // The ray intersects the plane.
        ++context.m_statistics->m_intersections_found;

        if(hit) {
            hit->m_object = this;
            hit->m_abscissa = t;    // world space
            hit->m_geometric_normal = Vector3(0.0, 1.0, 0.0);   // object space
            hit->m_shading_normal = hit->m_geometric_normal;    // object space
        }

        return true;
    }
}

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