/*
 * ShadowVolume.cpp
 *
 * Copyright (C) 2009 Matthias Schiffer <matthias@gamezock.de>
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License along
 * with this program. If not, see <http://www.gnu.org/licenses/>.
 */

#include "ShadowVolume.h"
#include "MathUtil.h"

#include "gl.h"

namespace Zoom {

ShadowVolume::ShadowVolume(const Triangle &t, const vmml::vec3f &lightPos) : visible(true) {
  MathUtil::Plane trianglePlane(t);

  for(int i = 0; i < 3; ++i) {
    rays[i].p = t.getVertex(i);
  }

  if(trianglePlane.isInFront(lightPos)) {
    visible = false;

    return;
  }

  for(int i = 0; i < 3; ++i) {
    rays[i].dir = rays[i].p - lightPos;
  }
}

void ShadowVolume::render() const {
  if(!visible)
    return;

  glVertex3fv(rays[0].p.array);
  glVertex3fv(rays[1].p.array);
  glVertex3fv(rays[2].p.array);

  for(int i = 0; i < 3; ++i) {
    const Ray &r1 = rays[i];
    const Ray &r2 = rays[(i+1)%3];

    glVertex3fv(r1.p.array);
    glVertex4fv(vmml::vec4f(r1.dir, 0).array);
    glVertex3fv(r2.p.array);

    glVertex3fv(r2.p.array);
    glVertex4fv(vmml::vec4f(r1.dir, 0).array);
    glVertex4fv(vmml::vec4f(r2.dir, 0).array);
  }

  glVertex4fv(vmml::vec4f(rays[2].dir, 0).array);
  glVertex4fv(vmml::vec4f(rays[1].dir, 0).array);
  glVertex4fv(vmml::vec4f(rays[0].dir, 0).array);
}

}