add option to do orthographic projection

include/openmc/plot.h

@@ -274,9 +274,6 @@ public:
 
 class ProjectionPlot : public PlottableInterface {
 
-  // TODO add optional choice between perspective or orthographic
-  // TODO add optionl to turn off wireframe
-
 public:
   ProjectionPlot(pugi::xml_node plot);
 
@@ -290,6 +287,7 @@ private:
   void set_field_of_view(pugi::xml_node node);
   void set_pixels(pugi::xml_node node);
   void set_opacities(pugi::xml_node node);
+  void set_orthographic_width(pugi::xml_node node);
 
   /* Used for drawing wireframe and colors. We record the list of
    * surface/cell/material intersections and the corresponding lengths as a ray
@@ -316,6 +314,12 @@ private:
   Direction up_ {0.0, 0.0, 1.0};    // which way is up
   bool wireframe_; // draw wireframe around ID boundaries (material or cell
                    // based on color_by)
+
+  /* The horizontal thickness, if using an orthographic projection.
+   * If set to zero, we assume using a perspective projection.
+   */
+  double orthographic_width_ {0.0};
+
   RGBColor wireframe_color_ {BLACK}; // wireframe color
   std::vector<double>
     xs_; // macro cross section values for cell volume rendering
@@ -332,6 +336,9 @@ private:
    */
   static bool trackstack_equivalent(const std::vector<TrackSegment>& track1,
     const std::vector<TrackSegment>& track2);
+
+  // Closed form 3x3 matrix inversion
+  static std::vector<double> invert_matrix(const std::vector<double>& input);
 };
 
 //===============================================================================

include/openmc/position.h

@@ -83,6 +83,11 @@ struct Position {
     return x * other.x + y * other.y + z * other.z;
   }
   inline double norm() const { return std::sqrt(x * x + y * y + z * z); }
+  inline Position cross(Position other) const
+  {
+    return {y * other.z - z * other.y, z * other.x - x * other.z,
+      x * other.y - y * other.x};
+  }
 
   //! Reflect a direction across a normal vector
   //! \param[in] other Vector to reflect across