/****************************************************************************

 Copyright (C) 2002-2008 Gilles Debunne. All rights reserved.

 This file is part of the QGLViewer library version 2.3.1.

 http://www.libqglviewer.com - contact@libqglviewer.com

 This file may be used under the terms of the GNU General Public License 
 versions 2.0 or 3.0 as published by the Free Software Foundation and
 appearing in the LICENSE file included in the packaging of this file.
 In addition, as a special exception, Gilles Debunne gives you certain 
 additional rights, described in the file GPL_EXCEPTION in this package.

 libQGLViewer uses dual licensing. Commercial/proprietary software must
 purchase a libQGLViewer Commercial License.

 This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

*****************************************************************************/

#include "clippingPlane.h"
#include "QGLViewer/manipulatedFrame.h"

using namespace std;
using namespace qglviewer;

// Draws a spiral
void Viewer::draw()
{
  const float nbSteps = 200.0;

  glBegin(GL_QUAD_STRIP);
  for (int i=0; i<nbSteps; ++i)
    {
      const float ratio = i/nbSteps;
      const float angle = 21.0*ratio;
      const float c = cos(angle);
      const float s = sin(angle);
      const float r1 = 1.0 - 0.8f*ratio;
      const float r2 = 0.8f - 0.8f*ratio;
      const float alt = ratio - 0.5f;
      const float nor = 0.5f;
      const float up = sqrt(1.0-nor*nor);
      glColor3f(1.0-ratio, 0.2f , ratio);
      glNormal3f(nor*c, up, nor*s);
      glVertex3f(r1*c, alt, r1*s);
      glVertex3f(r2*c, alt+0.05f, r2*s);
    }
  glEnd();


  glPushMatrix();
  glMultMatrixd(manipulatedFrame()->matrix());
  // Since the Clipping Plane equation is multiplied by the current modelView, we can define a 
  // constant equation (plane normal along Z and passing by the origin) since we are here in the
  // manipulatedFrame coordinates system (we glMultMatrixd() with the manipulatedFrame matrix()).
  static const GLdouble equation[] = { 0.0, 0.0, 1.0, 0.0 };
  glClipPlane(GL_CLIP_PLANE0, equation);
  
  // Draw a plane representation: Its normal...
  glColor3f(0.8f, 0.8f, 0.8f);
  drawArrow(0.4f, 0.015f);
  // ...and a quad (with a slightly shifted z so that it is not clipped).
  glBegin(GL_QUADS);
  glVertex3f(-1.0, -1.0, 0.001f);
  glVertex3f(-1.0,  1.0, 0.001f);
  glVertex3f( 1.0,  1.0, 0.001f);
  glVertex3f( 1.0, -1.0, 0.001f);
  glEnd();
  glPopMatrix();
}

void Viewer::init()
{
  // Restore previous viewer state.
  restoreStateFromFile();
  
  // Opens help window
  help();
  
  // The ManipulatedFrame will be used to position the clipping plane
  setManipulatedFrame(new ManipulatedFrame());
  
  // Enable plane clipping
  glEnable(GL_CLIP_PLANE0);
}

QString Viewer::helpString() const
{
  QString text("<h2>C l i p p i n g P l a n e</h2>");
  text += "The standard OpenGL <i>GL_CLIP_PLANE</i> feature is used to add an additionnal clipping ";
  text += "plane in the scene, which position and orientation are set by a <b>ManipulatedFrame</b>.<br><br>";
  text += "Hold the <b>Control</b> key pressed down while using the mouse to modify the plane orientation (left button) ";
  text += "and position (right button) and to interactively see the clipped result.<br><br>";
  text += "Since the plane equation is defined with respect to the current modelView matrix, a constant equation (normal";
  text += "along the Z axis) can be used since we transformed the coordinates system using the <b>matrix()</b> method.";

  return text;
}