[ggt-checkins] SF.net SVN: ggt:[1272] trunk

[<pat...@us...>]

Revision: 1272
          http://ggt.svn.sourceforge.net/ggt/?rev=1272&view=rev
Author:   patrickh
Date:     2011-03-27 18:11:00 +0000 (Sun, 27 Mar 2011)

Log Message:
-----------
Added an overload of gmtl::findClosestPt() for use with gmtl::Tri<T> and
gmtl::Point<T, 3>.

Submitted by: Sebastian Messerschmidt

Modified Paths:
--------------
    trunk/ChangeLog
    trunk/gmtl/TriOps.h

Modified: trunk/ChangeLog
===================================================================
--- trunk/ChangeLog	2011-03-27 17:31:11 UTC (rev 1271)
+++ trunk/ChangeLog	2011-03-27 18:11:00 UTC (rev 1272)
@@ -1,5 +1,8 @@
 DATE       AUTHOR       CHANGE
 ---------- ------------ -------------------------------------------------------
+2011-03-27 patrickh     Added an overload of gmtl::findClosestPt() for use with
+                        gmtl::Tri<T> and gmtl::Point<T, 3>.
+                        Submitted by Sebastian Messerschmidt
 2011-03-27 patrickh     Added an overload of gmtl::intersectDoubleSided() for
                         Tri/LineSeg intersection that ignores the triangle
                         winding.

Modified: trunk/gmtl/TriOps.h
===================================================================
--- trunk/gmtl/TriOps.h	2011-03-27 17:31:11 UTC (rev 1271)
+++ trunk/gmtl/TriOps.h	2011-03-27 18:11:00 UTC (rev 1272)
@@ -18,6 +18,83 @@
  */
 
 /**
+ * Finds the closest point on the triangle to a given point.
+ *
+ * @param tri The triangle to test.
+ * @param pt  The point which to test against triangle.
+ *
+ * @return  the point on the line segment closest to pt.
+ *
+ * @since 0.7.0
+ */
+template< class DATA_TYPE >
+Point<DATA_TYPE, 3> findNearestPt(const Tri<DATA_TYPE>& tri,
+                                  const Point<DATA_TYPE, 3>& pt)
+{
+   // inspired by Real Time Collision Detection 1st Edition p. 144 ff
+   Vec<DATA_TYPE, 3> ab = tri.edge(0,1);
+   Vec<DATA_TYPE, 3> ac = tri.edge(0,2);   
+   Vec<DATA_TYPE, 3> ap = pt - tri.mVerts[0]; // p - a 
+
+   // check if P in vertex region outside a
+   DATA_TYPE d1 = dot(ab, ap);
+   DATA_TYPE d2 = dot(ac, ap);
+   if (d1 <= 0.0 && d2 <= 0.0)
+   {
+      return tri.mVerts[0];
+   }
+
+// check if P in vertex region outside b
+   Vec<DATA_TYPE, 3> bp = pt - tri.mVerts[1]; // p -b
+   DATA_TYPE d3 = dot(ab, bp);
+   DATA_TYPE d4 = dot(ac, bp);
+
+   if (d3 >= 0 && d4 <= d3)
+   {
+      return tri.mVerts[1];
+   }
+
+   // check if p in edge region of AB, if true return projection of P onto AB
+   DATA_TYPE vc = d1*d4 - d3*d2;
+   if (vc <= 0.0 && d1 >= 0.0 && d3 <= 0.0)
+   {
+      DATA_TYPE v = d1 / (d1 - d3);
+      return tri.mVerts[0] + v * ab;
+   }
+
+   // check if P in vertex region outside c
+   Vec<DATA_TYPE, 3> cp = pt - tri.mVerts[2]; // p - c
+   DATA_TYPE d5 = dot(ab, cp);
+   DATA_TYPE d6 = dot(ac, cp);
+   if (d6 >= 0.0 && d5 <= d6)
+   {
+      return tri.mVerts[2];
+   }
+
+   // check if p in edge region of AC, if true return projection of P onto AC
+   DATA_TYPE vb = (d5 * d2) - (d1 * d6);
+   if (vb <= 0.0 && d2 >= 0.0 && d6 <= 0.0)
+   {
+      DATA_TYPE w = d2 / (d2 - d6);
+      return tri.mVerts[0] + w * ac;
+   }
+
+   // check if p in edge region of BC, if true return projection of P onto BC
+   DATA_TYPE va = (d3 * d6) - (d5 * d4);
+   if (va <= 0.0 && (d4 -d3) >= 0.0 && (d5 - d6) >= 0.0)
+   {
+      DATA_TYPE w = (d4 -d3) / ((d4 - d3) + (d5 -d6));
+      return tri.mVerts[1] + w * (tri.edge(1,2));
+   }
+
+   // P inside face region Compute Q trough barycentric coordinates
+   DATA_TYPE denom = 1.0 / (va + vb + vc);
+   DATA_TYPE v = vb * denom;
+   DATA_TYPE w = vc * denom;
+   return (tri.mVerts[0] + (ab * v) + (ac * w));
+} 
+
+/**
  * Computes the point at the center of the given triangle.
  *
  * @param tri     the triangle to find the center of


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