--- ray/src/hd/sm_geom.c	1998/08/20 16:47:21	3.2
+++ ray/src/hd/sm_geom.c	1998/08/25 11:03:28	3.3
@@ -984,6 +984,81 @@ FVECT v;
 
 
 
+/*
+ * int
+ * smRay(FVECT orig, FVECT dir,FVECT v0,FVECT v1,FVECT v2,FVECT r) 
+ *
+ *   Intersect the ray with triangle v0v1v2, return intersection point in r
+ *
+ *    Assumes orig,v0,v1,v2 are in spherical coordinates, and orig is
+ *    unit
+ */
+int
+traceRay(orig,dir,v0,v1,v2,r)
+  FVECT orig,dir;
+  FVECT v0,v1,v2;
+  FVECT r;
+{
+  FVECT n,p[3],d;
+  double pt[3],r_eps;
+  char i;
+  int which;
+
+  /* Find the plane equation for the triangle defined by the edge v0v1 and
+   the view center*/
+  VCROSS(n,v0,v1);
+  /* Intersect the ray with this plane */
+  i = intersect_ray_plane(orig,dir,n,0.0,&(pt[0]),p[0]);
+  if(i)
+    which = 0;
+  else
+    which = -1;
+
+  VCROSS(n,v1,v2);
+  i = intersect_ray_plane(orig,dir,n,0.0,&(pt[1]),p[1]);
+  if(i)
+    if((which==-1) || pt[1] < pt[0])
+      which = 1;
+
+  VCROSS(n,v2,v0);
+  i = intersect_ray_plane(orig,dir,n,0.0,&(pt[2]),p[2]);
+  if(i)
+    if((which==-1) || pt[2] < pt[which])
+      which = 2;
+
+  if(which != -1)
+  {
+      /* Return point that is K*eps along projection of the ray on
+	 the sphere to push intersection point p[which] into next cell
+      */
+      normalize(p[which]);
+      /* Calculate the ray perpendicular to the intersection point: approx
+       the direction moved along the sphere a distance of K*epsilon*/
+      r_eps = -DOT(p[which],dir);
+      VSUM(n,dir,p[which],r_eps);
+     /* Calculate the length along ray p[which]-dir needed to move to
+	 cause a move along the sphere of k*epsilon
+       */
+       r_eps = DOT(n,dir); 
+      VSUM(r,p[which],dir,(20*FTINY)/r_eps);
+      normalize(r);
+      return(TRUE);
+  }
+  else
+  {
+      /* Unable to find intersection: move along ray and try again */
+      r_eps = -DOT(orig,dir);
+      VSUM(n,dir,orig,r_eps);
+      r_eps = DOT(n,dir); 
+      VSUM(r,orig,dir,(20*FTINY)/r_eps);
+      normalize(r);
+#ifdef DEBUG
+      eputs("traceRay:Ray does not intersect triangle");
+#endif 
+      return(FALSE);
+  }
+}
+