[Teem-commit] SF.net SVN: teem:[3885] teem/trunk/src

[<ts...@us...>]

Revision: 3885
          http://teem.svn.sourceforge.net/teem/?rev=3885&view=rev
Author:   tststs
Date:     2008-08-20 08:40:05 +0000 (Wed, 20 Aug 2008)

Log Message:
-----------
limn: Replaced angle weighting with area weighting for normal estimation to
avoid problems with degenerate triangles.

ell: Added some more ELL_2V macros.

Modified Paths:
--------------
    teem/trunk/src/ell/ellMacros.h
    teem/trunk/src/limn/polydata.c

Modified: teem/trunk/src/ell/ellMacros.h
===================================================================
--- teem/trunk/src/ell/ellMacros.h	2008-08-12 14:56:02 UTC (rev 3884)
+++ teem/trunk/src/ell/ellMacros.h	2008-08-20 08:40:05 UTC (rev 3885)
@@ -95,6 +95,29 @@
 #define ELL_2V_COPY(v2, v1) \
   ((v2)[0] = (v1)[0], (v2)[1] = (v1)[1])
 
+#define ELL_2V_INCR(v2, v1) \
+  ((v2)[0] += (v1)[0],      \
+   (v2)[1] += (v1)[1])
+
+#define ELL_2V_ADD2(v3, v1, v2) \
+  ((v3)[0] = (v1)[0] + (v2)[0], \
+   (v3)[1] = (v1)[1] + (v2)[1])
+
+#define ELL_2V_ADD3(v4, v1, v2, v3)       \
+  ((v4)[0] = (v1)[0] + (v2)[0] + (v3)[0], \
+   (v4)[1] = (v1)[1] + (v2)[1] + (v3)[1])
+
+#define ELL_2V_ADD4(v5, v1, v2, v3, v4)       \
+  ((v5)[0] = (v1)[0] + (v2)[0] + (v3)[0] + (v4)[0], \
+   (v5)[1] = (v1)[1] + (v2)[1] + (v3)[1] + (v4)[1])
+
+#define ELL_2V_SUB(v3, v1, v2)  \
+  ((v3)[0] = (v1)[0] - (v2)[0], \
+   (v3)[1] = (v1)[1] - (v2)[1])
+
+#define ELL_2V_COPY(v2, v1) \
+  ((v2)[0] = (v1)[0], (v2)[1] = (v1)[1])
+
 #define ELL_2V_DOT(v1, v2) ((v1)[0]*(v2)[0] + (v1)[1]*(v2)[1])
 
 #define ELL_2V_LEN(v) (sqrt(ELL_2V_DOT((v),(v))))

Modified: teem/trunk/src/limn/polydata.c
===================================================================
--- teem/trunk/src/limn/polydata.c	2008-08-12 14:56:02 UTC (rev 3884)
+++ teem/trunk/src/limn/polydata.c	2008-08-20 08:40:05 UTC (rev 3885)
@@ -405,17 +405,17 @@
           ELL_34V_HOMOG(pos[ii], pld->xyzw + 4*indxLine[ii]);
         }
         ELL_3V_SUB(edgeA, pos[1], pos[0]);
-        ELL_3V_NORM_TT(edgeA, float, edgeA, len);
         ELL_3V_SUB(edgeB, pos[2], pos[0]);
-        ELL_3V_NORM_TT(edgeB, float, edgeB, len);
         ELL_3V_CROSS(norm, edgeA, edgeB);
-        ELL_3V_NORM_TT(norm, float, norm, len);
-        ELL_3V_ADD2(sum, edgeA, edgeB);
-        ELL_3V_SUB(dif, edgeA, edgeB);
-        /* wght is angle between edges, as per redbook Appendix E */
-        wght = 2*AIR_CAST(float, atan2(ELL_3V_LEN(dif), ELL_3V_LEN(sum)));
+	/* Adding cross products without any normalization is
+	 * equivalent to weighting by triangle area, as proposed
+	 * (among others) by G. Taubin ("Estimating the tensor of
+	 * curvature of a surface from a polyhedral approximation",
+	 * ICCV 1995). This is efficient, avoids trouble with
+	 * degenerate triangles and gives reasonable results in
+	 * practice. */
         for (ii=0; ii<3; ii++) {
-          ELL_3V_SCALE_INCR(pld->norm + 3*indxLine[ii], wght, norm);
+	  ELL_3V_INCR(pld->norm + 3*indxLine[ii], norm);
         }
       }
     }


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