--- /dev/null
+/*
+** License Applicability. Except to the extent portions of this file are
+** made subject to an alternative license as permitted in the SGI Free
+** Software License B, Version 1.1 (the "License"), the contents of this
+** file are subject only to the provisions of the License. You may not use
+** this file except in compliance with the License. You may obtain a copy
+** of the License at Silicon Graphics, Inc., attn: Legal Services, 1600
+** Amphitheatre Parkway, Mountain View, CA 94043-1351, or at:
+**
+** http://oss.sgi.com/projects/FreeB
+**
+** Note that, as provided in the License, the Software is distributed on an
+** "AS IS" basis, with ALL EXPRESS AND IMPLIED WARRANTIES AND CONDITIONS
+** DISCLAIMED, INCLUDING, WITHOUT LIMITATION, ANY IMPLIED WARRANTIES AND
+** CONDITIONS OF MERCHANTABILITY, SATISFACTORY QUALITY, FITNESS FOR A
+** PARTICULAR PURPOSE, AND NON-INFRINGEMENT.
+**
+** Original Code. The Original Code is: OpenGL Sample Implementation,
+** Version 1.2.1, released January 26, 2000, developed by Silicon Graphics,
+** Inc. The Original Code is Copyright (c) 1991-2000 Silicon Graphics, Inc.
+** Copyright in any portions created by third parties is as indicated
+** elsewhere herein. All Rights Reserved.
+**
+** Additional Notice Provisions: The application programming interfaces
+** established by SGI in conjunction with the Original Code are The
+** OpenGL(R) Graphics System: A Specification (Version 1.2.1), released
+** April 1, 1999; The OpenGL(R) Graphics System Utility Library (Version
+** 1.3), released November 4, 1998; and OpenGL(R) Graphics with the X
+** Window System(R) (Version 1.3), released October 19, 1998. This software
+** was created using the OpenGL(R) version 1.2.1 Sample Implementation
+** published by SGI, but has not been independently verified as being
+** compliant with the OpenGL(R) version 1.2.1 Specification.
+**
+*/
+/*
+** Author: Eric Veach, July 1994.
+**
+*/
+
+#include "gluos.h"
+#include "mesh.h"
+#include "tess.h"
+#include "normal.h"
+#include <math.h>
+#include <assert.h>
+
+#define TRUE 1
+#define FALSE 0
+
+#define Dot(u,v) (u[0]*v[0] + u[1]*v[1] + u[2]*v[2])
+
+#if 0
+static void Normalize( GLdouble v[3] )
+{
+ GLdouble len = v[0]*v[0] + v[1]*v[1] + v[2]*v[2];
+
+ assert( len > 0 );
+ len = sqrt( len );
+ v[0] /= len;
+ v[1] /= len;
+ v[2] /= len;
+}
+#endif
+
+#undef ABS
+#define ABS(x) ((x) < 0 ? -(x) : (x))
+
+static int LongAxis( GLdouble v[3] )
+{
+ int i = 0;
+
+ if( ABS(v[1]) > ABS(v[0]) ) { i = 1; }
+ if( ABS(v[2]) > ABS(v[i]) ) { i = 2; }
+ return i;
+}
+
+static void ComputeNormal( GLUtesselator *tess, GLdouble norm[3] )
+{
+ GLUvertex *v, *v1, *v2;
+ GLdouble c, tLen2, maxLen2;
+ GLdouble maxVal[3], minVal[3], d1[3], d2[3], tNorm[3];
+ GLUvertex *maxVert[3], *minVert[3];
+ GLUvertex *vHead = &tess->mesh->vHead;
+ int i;
+
+ maxVal[0] = maxVal[1] = maxVal[2] = -2 * GLU_TESS_MAX_COORD;
+ minVal[0] = minVal[1] = minVal[2] = 2 * GLU_TESS_MAX_COORD;
+
+ for( v = vHead->next; v != vHead; v = v->next ) {
+ for( i = 0; i < 3; ++i ) {
+ c = v->coords[i];
+ if( c < minVal[i] ) { minVal[i] = c; minVert[i] = v; }
+ if( c > maxVal[i] ) { maxVal[i] = c; maxVert[i] = v; }
+ }
+ }
+
+ /* Find two vertices separated by at least 1/sqrt(3) of the maximum
+ * distance between any two vertices
+ */
+ i = 0;
+ if( maxVal[1] - minVal[1] > maxVal[0] - minVal[0] ) { i = 1; }
+ if( maxVal[2] - minVal[2] > maxVal[i] - minVal[i] ) { i = 2; }
+ if( minVal[i] >= maxVal[i] ) {
+ /* All vertices are the same -- normal doesn't matter */
+ norm[0] = 0; norm[1] = 0; norm[2] = 1;
+ return;
+ }
+
+ /* Look for a third vertex which forms the triangle with maximum area
+ * (Length of normal == twice the triangle area)
+ */
+ maxLen2 = 0;
+ v1 = minVert[i];
+ v2 = maxVert[i];
+ d1[0] = v1->coords[0] - v2->coords[0];
+ d1[1] = v1->coords[1] - v2->coords[1];
+ d1[2] = v1->coords[2] - v2->coords[2];
+ for( v = vHead->next; v != vHead; v = v->next ) {
+ d2[0] = v->coords[0] - v2->coords[0];
+ d2[1] = v->coords[1] - v2->coords[1];
+ d2[2] = v->coords[2] - v2->coords[2];
+ tNorm[0] = d1[1]*d2[2] - d1[2]*d2[1];
+ tNorm[1] = d1[2]*d2[0] - d1[0]*d2[2];
+ tNorm[2] = d1[0]*d2[1] - d1[1]*d2[0];
+ tLen2 = tNorm[0]*tNorm[0] + tNorm[1]*tNorm[1] + tNorm[2]*tNorm[2];
+ if( tLen2 > maxLen2 ) {
+ maxLen2 = tLen2;
+ norm[0] = tNorm[0];
+ norm[1] = tNorm[1];
+ norm[2] = tNorm[2];
+ }
+ }
+
+ if( maxLen2 <= 0 ) {
+ /* All points lie on a single line -- any decent normal will do */
+ norm[0] = norm[1] = norm[2] = 0;
+ norm[LongAxis(d1)] = 1;
+ }
+}
+
+
+static void CheckOrientation( GLUtesselator *tess )
+{
+ GLdouble area;
+ GLUface *f, *fHead = &tess->mesh->fHead;
+ GLUvertex *v, *vHead = &tess->mesh->vHead;
+ GLUhalfEdge *e;
+
+ /* When we compute the normal automatically, we choose the orientation
+ * so that the the sum of the signed areas of all contours is non-negative.
+ */
+ area = 0;
+ for( f = fHead->next; f != fHead; f = f->next ) {
+ e = f->anEdge;
+ if( e->winding <= 0 ) continue;
+ do {
+ area += (e->Org->s - e->Dst->s) * (e->Org->t + e->Dst->t);
+ e = e->Lnext;
+ } while( e != f->anEdge );
+ }
+ if( area < 0 ) {
+ /* Reverse the orientation by flipping all the t-coordinates */
+ for( v = vHead->next; v != vHead; v = v->next ) {
+ v->t = - v->t;
+ }
+ tess->tUnit[0] = - tess->tUnit[0];
+ tess->tUnit[1] = - tess->tUnit[1];
+ tess->tUnit[2] = - tess->tUnit[2];
+ }
+}
+
+#ifdef FOR_TRITE_TEST_PROGRAM
+#include <stdlib.h>
+extern int RandomSweep;
+#define S_UNIT_X (RandomSweep ? (2*drand48()-1) : 1.0)
+#define S_UNIT_Y (RandomSweep ? (2*drand48()-1) : 0.0)
+#else
+#if defined(SLANTED_SWEEP)
+/* The "feature merging" is not intended to be complete. There are
+ * special cases where edges are nearly parallel to the sweep line
+ * which are not implemented. The algorithm should still behave
+ * robustly (ie. produce a reasonable tesselation) in the presence
+ * of such edges, however it may miss features which could have been
+ * merged. We could minimize this effect by choosing the sweep line
+ * direction to be something unusual (ie. not parallel to one of the
+ * coordinate axes).
+ */
+#define S_UNIT_X 0.50941539564955385 /* Pre-normalized */
+#define S_UNIT_Y 0.86052074622010633
+#else
+#define S_UNIT_X 1.0
+#define S_UNIT_Y 0.0
+#endif
+#endif
+
+/* Determine the polygon normal and project vertices onto the plane
+ * of the polygon.
+ */
+void __gl_projectPolygon( GLUtesselator *tess )
+{
+ GLUvertex *v, *vHead = &tess->mesh->vHead;
+ GLdouble norm[3];
+ GLdouble *sUnit, *tUnit;
+ int i, computedNormal = FALSE;
+
+ norm[0] = tess->normal[0];
+ norm[1] = tess->normal[1];
+ norm[2] = tess->normal[2];
+ if( norm[0] == 0 && norm[1] == 0 && norm[2] == 0 ) {
+ ComputeNormal( tess, norm );
+ computedNormal = TRUE;
+ }
+ sUnit = tess->sUnit;
+ tUnit = tess->tUnit;
+ i = LongAxis( norm );
+
+#if defined(FOR_TRITE_TEST_PROGRAM) || defined(TRUE_PROJECT)
+ /* Choose the initial sUnit vector to be approximately perpendicular
+ * to the normal.
+ */
+ Normalize( norm );
+
+ sUnit[i] = 0;
+ sUnit[(i+1)%3] = S_UNIT_X;
+ sUnit[(i+2)%3] = S_UNIT_Y;
+
+ /* Now make it exactly perpendicular */
+ w = Dot( sUnit, norm );
+ sUnit[0] -= w * norm[0];
+ sUnit[1] -= w * norm[1];
+ sUnit[2] -= w * norm[2];
+ Normalize( sUnit );
+
+ /* Choose tUnit so that (sUnit,tUnit,norm) form a right-handed frame */
+ tUnit[0] = norm[1]*sUnit[2] - norm[2]*sUnit[1];
+ tUnit[1] = norm[2]*sUnit[0] - norm[0]*sUnit[2];
+ tUnit[2] = norm[0]*sUnit[1] - norm[1]*sUnit[0];
+ Normalize( tUnit );
+#else
+ /* Project perpendicular to a coordinate axis -- better numerically */
+ sUnit[i] = 0;
+ sUnit[(i+1)%3] = S_UNIT_X;
+ sUnit[(i+2)%3] = S_UNIT_Y;
+
+ tUnit[i] = 0;
+ tUnit[(i+1)%3] = (norm[i] > 0) ? -S_UNIT_Y : S_UNIT_Y;
+ tUnit[(i+2)%3] = (norm[i] > 0) ? S_UNIT_X : -S_UNIT_X;
+#endif
+
+ /* Project the vertices onto the sweep plane */
+ for( v = vHead->next; v != vHead; v = v->next ) {
+ v->s = Dot( v->coords, sUnit );
+ v->t = Dot( v->coords, tUnit );
+ }
+ if( computedNormal ) {
+ CheckOrientation( tess );
+ }
+}
Ecere Software / sdk / blobdiff