/*
 * Adapted from Open Shading Language with this license:
 *
 * Copyright (c) 2009-2010 Sony Pictures Imageworks Inc., et al.
 * All Rights Reserved.
 *
 * Modifications Copyright 2011, Blender Foundation.
 *
 * 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 Sony Pictures Imageworks 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 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef CCL_OSLUTIL_H
#define CCL_OSLUTIL_H

// Return wireframe opacity factor [0, 1] given a geometry type in
// ("triangles", "polygons" or "patches"), and a line_width in raster
// or world space depending on the last (raster) boolean argument.
//
float wireframe(string edge_type, float line_width, int raster)
{
  // ray differentials are so big in diffuse context that this function would always return "wire"
  if (raytype("path:diffuse"))
    return 0.0;

  int np = 0;
  point p[64];
  float pixelWidth = 1;

  if (edge_type == "triangles") {
    np = 3;
    if (!getattribute("geom:trianglevertices", p))
      return 0.0;
  }
  else if (edge_type == "polygons" || edge_type == "patches") {
    getattribute("geom:numpolyvertices", np);
    if (np < 3 || !getattribute("geom:polyvertices", p))
      return 0.0;
  }

  if (raster) {
    // Project the derivatives of P to the viewing plane defined
    // by I so we have a measure of how big is a pixel at this point
    float pixelWidthX = length(Dx(P) - dot(Dx(P), I) * I);
    float pixelWidthY = length(Dy(P) - dot(Dy(P), I) * I);
    // Take the average of both axis' length
    pixelWidth = (pixelWidthX + pixelWidthY) / 2;
  }

  // Use half the width as the neighbor face will render the
  // other half. And take the square for fast comparison
  pixelWidth *= 0.5 * line_width;
  pixelWidth *= pixelWidth;
  for (int i = 0; i < np; i++) {
    int i2 = i ? i - 1 : np - 1;
    vector dir = P - p[i];
    vector edge = p[i] - p[i2];
    vector crs = cross(edge, dir);
    // At this point dot(crs, crs) / dot(edge, edge) is
    // the square of area / length(edge) == square of the
    // distance to the edge.
    if (dot(crs, crs) < (dot(edge, edge) * pixelWidth))
      return 1;
  }
  return 0;
}

float wireframe(string edge_type, float line_width)
{
  return wireframe(edge_type, line_width, 1);
}
float wireframe(string edge_type)
{
  return wireframe(edge_type, 1.0, 1);
}
float wireframe()
{
  return wireframe("polygons", 1.0, 1);
}

#endif /* CCL_OSLUTIL_H */
