The GtkRadiant sources as originally released under the GPL license.

libs/mathlib/ray.c

@@ -0,0 +1,140 @@
+/*
+Copyright (C) 2001-2006, William Joseph.
+All Rights Reserved.
+
+This file is part of GtkRadiant.
+
+GtkRadiant is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+GtkRadiant 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 GtkRadiant; if not, write to the Free Software
+Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+#include "mathlib.h"
+#include <float.h>
+
+vec3_t identity = { 0,0,0 };
+
+void ray_construct_for_vec3(ray_t *ray, const vec3_t origin, const vec3_t direction)
+{
+  VectorCopy(origin, ray->origin);
+  VectorCopy(direction, ray->direction);
+}
+  
+void ray_transform(ray_t *ray, const m4x4_t matrix)
+{
+  m4x4_transform_point(matrix, ray->origin);
+  m4x4_transform_normal(matrix, ray->direction);
+}
+
+vec_t ray_intersect_point(const ray_t *ray, const vec3_t point, vec_t epsilon, vec_t divergence)
+{
+  vec3_t displacement;
+  vec_t depth;
+
+  // calc displacement of test point from ray origin
+  VectorSubtract(point, ray->origin, displacement);
+  // calc length of displacement vector along ray direction
+	depth = DotProduct(displacement, ray->direction);
+  if(depth < 0.0f) return (vec_t)FLT_MAX;
+  // calc position of closest point on ray to test point
+  VectorMA (ray->origin, depth, ray->direction, displacement);
+  // calc displacement of test point from closest point
+	VectorSubtract(point, displacement, displacement);
+  // calc length of displacement, subtract depth-dependant epsilon
+  if (VectorLength(displacement) - (epsilon + (depth * divergence)) > 0.0f) return (vec_t)FLT_MAX;
+  return depth;
+}
+
+// Tomas Moller and Ben Trumbore. Fast, minimum storage ray-triangle intersection. Journal of graphics tools, 2(1):21-28, 1997
+
+#define EPSILON 0.000001
+
+vec_t ray_intersect_triangle(const ray_t *ray, qboolean bCullBack, const vec3_t vert0, const vec3_t vert1, const vec3_t vert2)
+{
+  float edge1[3], edge2[3], tvec[3], pvec[3], qvec[3];
+  float det,inv_det;
+  float u, v;
+  vec_t depth = (vec_t)FLT_MAX;
+  
+  /* find vectors for two edges sharing vert0 */
+  VectorSubtract(vert1, vert0, edge1);
+  VectorSubtract(vert2, vert0, edge2);
+  
+  /* begin calculating determinant - also used to calculate U parameter */
+  CrossProduct(ray->direction, edge2, pvec);
+  
+  /* if determinant is near zero, ray lies in plane of triangle */
+  det = DotProduct(edge1, pvec);
+  
+  if (bCullBack == qtrue)
+  {
+    if (det < EPSILON)
+      return depth;
+    
+    // calculate distance from vert0 to ray origin
+    VectorSubtract(ray->origin, vert0, tvec);
+    
+    // calculate U parameter and test bounds
+    u = DotProduct(tvec, pvec);
+    if (u < 0.0 || u > det)
+      return depth;
+    
+    // prepare to test V parameter
+    CrossProduct(tvec, edge1, qvec);
+    
+    // calculate V parameter and test bounds
+    v = DotProduct(ray->direction, qvec);
+    if (v < 0.0 || u + v > det)
+      return depth;
+    
+    // calculate t, scale parameters, ray intersects triangle
+    depth = DotProduct(edge2, qvec);
+    inv_det = 1.0f / det;
+    depth *= inv_det;
+    //u *= inv_det;
+    //v *= inv_det;
+  }
+  else
+  {
+    /* the non-culling branch */
+    if (det > -EPSILON && det < EPSILON)
+      return depth;
+    inv_det = 1.0f / det;
+    
+    /* calculate distance from vert0 to ray origin */
+    VectorSubtract(ray->origin, vert0, tvec);
+    
+    /* calculate U parameter and test bounds */
+    u = DotProduct(tvec, pvec) * inv_det;
+    if (u < 0.0 || u > 1.0)
+      return depth;
+    
+    /* prepare to test V parameter */
+    CrossProduct(tvec, edge1, qvec);
+    
+    /* calculate V parameter and test bounds */
+    v = DotProduct(ray->direction, qvec) * inv_det;
+    if (v < 0.0 || u + v > 1.0)
+      return depth;
+    
+    /* calculate t, ray intersects triangle */
+    depth = DotProduct(edge2, qvec) * inv_det;
+  }
+  return depth;
+}
+
+vec_t ray_intersect_plane(const ray_t* ray, const vec3_t normal, vec_t dist)
+{
+  return -(DotProduct(normal, ray->origin) - dist) / DotProduct(ray->direction, normal);
+}
+