text: /*
      This file is part of Mitsuba, a physically based rendering system.
  
      Copyright (c) 2007-2014 by Wenzel Jakob and others.
  
      Mitsuba is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License Version 3
      as published by the Free Software Foundation.
  
      Mitsuba 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 this program. If not, see <http://www.gnu.org/licenses/>.
  */
  
  #include <mitsuba/render/texture.h>
  #include <mitsuba/render/trimesh.h>
  #include <mitsuba/core/properties.h>
  #include <mitsuba/hw/basicshader.h>
  
  MTS_NAMESPACE_BEGIN
  
  /*!\plugin{wireframe}{Wireframe texture}
   * \order{6}
   * \parameters{
   *     \parameter{interiorColor}{\Spectrum}{
   *       Color value of the interior of triangles
   *       \default{0.5}
   *     }
   *     \parameter{edgeColor}{\Spectrum}{
   *       Edge color value
   *       \default{0.1}
   *     }
   *     \parameter{lineWidth}{\Float}{
   *        World-space width of the mesh edges
   *        \default{automatic}
   *     }
   *     \parameter{stepWidth}{\Float}{
   *        Controls the width of the step function used for the
   *        color transition. It is specified as a value between zero
   *        and one (relative to the \code{lineWidth} parameter)
   *        \default{0.5}
   *     }
   * }
   * \renderings{
   *     \rendering{Wireframe texture applied to the material test object}{tex_wireframe}
   * }
   *
   * This plugin implements a simple two-color wireframe texture map
   * that reveals the structure of a triangular mesh.
   */
  class WireFrame : public Texture {
  public:
      WireFrame(const Properties &props) : Texture(props) {
          m_lineWidth = props.getFloat("lineWidth", 0.0f);
          m_stepWidth = props.getFloat("stepWidth", 0.5f);
          m_edgeColor = props.getSpectrum("edgeColor", Spectrum(0.1f));
          m_interiorColor = props.getSpectrum("interiorColor", Spectrum(.5f));
          m_stepWidth = std::max((Float) 0.0f, std::min(m_stepWidth, (Float) 1.0f));
          m_mutex = new Mutex();
      }
  
      WireFrame(Stream *stream, InstanceManager *manager)
       : Texture(stream, manager) {
          m_mutex = new Mutex();
          m_edgeColor = Spectrum(stream);
          m_interiorColor = Spectrum(stream);
          m_lineWidth = stream->readFloat();
      }
  
      void serialize(Stream *stream, InstanceManager *manager) const {
          Texture::serialize(stream, manager);
          m_edgeColor.serialize(stream);
          m_interiorColor.serialize(stream);
          stream->writeFloat(m_lineWidth);
      }
  
      Spectrum eval(const Intersection &its, bool /* unused */) const {
          if (!its.shape->getClass()->derivesFrom(MTS_CLASS(TriMesh)))
              return m_interiorColor;
  
          const TriMesh *triMesh = static_cast<const TriMesh *>(its.shape);
          const Point *positions = triMesh->getVertexPositions();
          if (its.primIndex >= triMesh->getTriangleCount())
              return m_interiorColor;
  
          if (m_lineWidth == 0) {
              /* Somewhat hacky but probably helpful in many cases.
                 This tries to find a suitable line width, which is set
                 to 10% of the average average edge length */
              LockGuard lock(m_mutex);
              if (m_lineWidth == 0) {
                  Float lineWidth = 0;
                  for (size_t i=0; i<triMesh->getTriangleCount(); ++i) {
                      const Triangle &tri = triMesh->getTriangles()[i];
                      for (int j=0; j<3; ++j)
                          lineWidth += (positions[tri.idx[j]]
                              - positions[tri.idx[(j+1)%3]]).length();
                  }
  
                  m_lineWidth = 0.1f * lineWidth / (3 * triMesh->getTriangleCount());
              }
          }
  
          const Triangle &tri = triMesh->getTriangles()[its.primIndex];
  
          Float minDist = std::numeric_limits<Float>::infinity();
          for (int i=0; i<3; ++i) {
              const Point& cur  = positions[tri.idx[i]];
              const Point& next = positions[tri.idx[(i+1)%3]];
  
              Vector d1 = normalize(next - cur),
                     d2 = its.p - cur;
  
              minDist = std::min(minDist, (cur + d1 * dot(d1, d2) - its.p).lengthSquared());
          }
  
          Float a = math::smoothStep(m_lineWidth*(1.f-m_stepWidth), m_lineWidth, std::sqrt(minDist));
          return m_edgeColor*(1-a) + m_interiorColor*a;
      }
  
      bool usesRayDifferentials() const {
          return false;
      }
  
      Spectrum getAverage() const {
          Spectrum value;
          /* Approximate ... */
          for (int i=0; i<SPECTRUM_SAMPLES; ++i)
              value[i] = 0.5f * (m_edgeColor[i] + m_interiorColor[i]);
          return value;
      }
  
      Spectrum getMinimum() const {
          Spectrum value;
          for (int i=0; i<SPECTRUM_SAMPLES; ++i)
              value[i] = std::min(m_edgeColor[i], m_interiorColor[i]);
          return value;
      }
  
      Spectrum getMaximum() const {
          Spectrum value;
          for (int i=0; i<SPECTRUM_SAMPLES; ++i)
              value[i] = std::max(m_edgeColor[i], m_interiorColor[i]);
          return value;
      }
  
      bool isConstant() const {
          return false;
      }
  
      bool isMonochromatic() const {
          return Spectrum(m_edgeColor[0]) == m_edgeColor
              && Spectrum(m_interiorColor[0]) == m_interiorColor;
      }
  
      std::string toString() const {
          std::ostringstream oss;
          oss << "WireFrame[" << endl
              << "  edgeColor = " << m_edgeColor.toString() << "," << endl
              << "  interiorColor = " << m_interiorColor.toString() << "," << endl
              << "  lineWidth = " << m_lineWidth << endl
              << "  stepWidth = " << m_stepWidth << endl
              << "]";
          return oss.str();
      }
  
      Shader *createShader(Renderer *renderer) const;
  
      MTS_DECLARE_CLASS()
  protected:
      mutable Float m_lineWidth;
      mutable ref<Mutex> m_mutex;
      Float m_stepWidth;
      Spectrum m_edgeColor;
      Spectrum m_interiorColor;
  };
  
  // ================ Hardware shader implementation ================
  
  class WireFrameShader : public Shader {
  public:
      WireFrameShader(Renderer *renderer, const Spectrum &value)
          : Shader(renderer, ETextureShader), m_value(value) {
      }
  
      void generateCode(std::ostringstream &oss,
              const std::string &evalName,
              const std::vector<std::string> &depNames) const {
          oss << "uniform vec3 " << evalName << "_value;" << endl
              << endl
              << "vec3 " << evalName << "(vec2 uv) {" << endl
              << "    return " << evalName << "_value;" << endl
              << "}" << endl;
      }
  
      void resolve(const GPUProgram *program, const std::string &evalName, std::vector<int> &parameterIDs) const {
          parameterIDs.push_back(program->getParameterID(evalName + "_value", false));
      }
  
      void bind(GPUProgram *program, const std::vector<int> &parameterIDs, int &textureUnitOffset) const {
          program->setParameter(parameterIDs[0], m_value);
      }
  
      MTS_DECLARE_CLASS()
  private:
      Spectrum m_value;
  };
  
  Shader *WireFrame::createShader(Renderer *renderer) const {
      return new WireFrameShader(renderer, m_interiorColor);
  }
  
  MTS_IMPLEMENT_CLASS(WireFrameShader, false, Shader)
  MTS_IMPLEMENT_CLASS_S(WireFrame, false, Texture)
  MTS_EXPORT_PLUGIN(WireFrame, "Wireframe texture");
  MTS_NAMESPACE_END
  