2 ** License Applicability. Except to the extent portions of this file are
3 ** made subject to an alternative license as permitted in the SGI Free
4 ** Software License B, Version 1.1 (the "License"), the contents of this
5 ** file are subject only to the provisions of the License. You may not use
6 ** this file except in compliance with the License. You may obtain a copy
7 ** of the License at Silicon Graphics, Inc., attn: Legal Services, 1600
8 ** Amphitheatre Parkway, Mountain View, CA 94043-1351, or at:
10 ** http://oss.sgi.com/projects/FreeB
12 ** Note that, as provided in the License, the Software is distributed on an
13 ** "AS IS" basis, with ALL EXPRESS AND IMPLIED WARRANTIES AND CONDITIONS
14 ** DISCLAIMED, INCLUDING, WITHOUT LIMITATION, ANY IMPLIED WARRANTIES AND
15 ** CONDITIONS OF MERCHANTABILITY, SATISFACTORY QUALITY, FITNESS FOR A
16 ** PARTICULAR PURPOSE, AND NON-INFRINGEMENT.
18 ** Original Code. The Original Code is: OpenGL Sample Implementation,
19 ** Version 1.2.1, released January 26, 2000, developed by Silicon Graphics,
20 ** Inc. The Original Code is Copyright (c) 1991-2000 Silicon Graphics, Inc.
21 ** Copyright in any portions created by third parties is as indicated
22 ** elsewhere herein. All Rights Reserved.
24 ** Additional Notice Provisions: The application programming interfaces
25 ** established by SGI in conjunction with the Original Code are The
26 ** OpenGL(R) Graphics System: A Specification (Version 1.2.1), released
27 ** April 1, 1999; The OpenGL(R) Graphics System Utility Library (Version
28 ** 1.3), released November 4, 1998; and OpenGL(R) Graphics with the X
29 ** Window System(R) (Version 1.3), released October 19, 1998. This software
30 ** was created using the OpenGL(R) version 1.2.1 Sample Implementation
31 ** published by SGI, but has not been independently verified as being
32 ** compliant with the OpenGL(R) version 1.2.1 Specification.
36 ** Author: Eric Veach, July 1994.
39 ** $Header: //depot/main/gfx/lib/glu/libtess/normal.c#5 $
52 #define Dot(u,v) (u[0]*v[0] + u[1]*v[1] + u[2]*v[2])
54 #if defined(FOR_TRITE_TEST_PROGRAM) || defined(TRUE_PROJECT)
55 static void Normalize( GLdouble v[3] )
57 GLdouble len = v[0]*v[0] + v[1]*v[1] + v[2]*v[2];
67 #define ABS(x) ((x) < 0 ? -(x) : (x))
69 static int LongAxis( GLdouble v[3] )
73 if( ABS(v[1]) > ABS(v[0]) ) { i = 1; }
74 if( ABS(v[2]) > ABS(v[i]) ) { i = 2; }
78 static void ComputeNormal( GLUtesselator *tess, GLdouble norm[3] )
80 GLUvertex *v, *v1, *v2;
81 GLdouble c, tLen2, maxLen2;
82 GLdouble maxVal[3], minVal[3], d1[3], d2[3], tNorm[3];
83 GLUvertex *maxVert[3], *minVert[3];
84 GLUvertex *vHead = &tess->mesh->vHead;
87 maxVal[0] = maxVal[1] = maxVal[2] = -2 * GLU_TESS_MAX_COORD;
88 minVal[0] = minVal[1] = minVal[2] = 2 * GLU_TESS_MAX_COORD;
90 for( v = vHead->next; v != vHead; v = v->next ) {
91 for( i = 0; i < 3; ++i ) {
93 if( c < minVal[i] ) { minVal[i] = c; minVert[i] = v; }
94 if( c > maxVal[i] ) { maxVal[i] = c; maxVert[i] = v; }
98 /* Find two vertices separated by at least 1/sqrt(3) of the maximum
99 * distance between any two vertices
102 if( maxVal[1] - minVal[1] > maxVal[0] - minVal[0] ) { i = 1; }
103 if( maxVal[2] - minVal[2] > maxVal[i] - minVal[i] ) { i = 2; }
104 if( minVal[i] >= maxVal[i] ) {
105 /* All vertices are the same -- normal doesn't matter */
106 norm[0] = 0; norm[1] = 0; norm[2] = 1;
110 /* Look for a third vertex which forms the triangle with maximum area
111 * (Length of normal == twice the triangle area)
116 d1[0] = v1->coords[0] - v2->coords[0];
117 d1[1] = v1->coords[1] - v2->coords[1];
118 d1[2] = v1->coords[2] - v2->coords[2];
119 for( v = vHead->next; v != vHead; v = v->next ) {
120 d2[0] = v->coords[0] - v2->coords[0];
121 d2[1] = v->coords[1] - v2->coords[1];
122 d2[2] = v->coords[2] - v2->coords[2];
123 tNorm[0] = d1[1]*d2[2] - d1[2]*d2[1];
124 tNorm[1] = d1[2]*d2[0] - d1[0]*d2[2];
125 tNorm[2] = d1[0]*d2[1] - d1[1]*d2[0];
126 tLen2 = tNorm[0]*tNorm[0] + tNorm[1]*tNorm[1] + tNorm[2]*tNorm[2];
127 if( tLen2 > maxLen2 ) {
136 /* All points lie on a single line -- any decent normal will do */
137 norm[0] = norm[1] = norm[2] = 0;
138 norm[LongAxis(d1)] = 1;
143 static void CheckOrientation( GLUtesselator *tess )
146 GLUface *f, *fHead = &tess->mesh->fHead;
147 GLUvertex *v, *vHead = &tess->mesh->vHead;
150 /* When we compute the normal automatically, we choose the orientation
151 * so that the the sum of the signed areas of all contours is non-negative.
154 for( f = fHead->next; f != fHead; f = f->next ) {
156 if( e->winding <= 0 ) continue;
158 area += (e->Org->s - e->Dst->s) * (e->Org->t + e->Dst->t);
160 } while( e != f->anEdge );
163 /* Reverse the orientation by flipping all the t-coordinates */
164 for( v = vHead->next; v != vHead; v = v->next ) {
167 tess->tUnit[0] = - tess->tUnit[0];
168 tess->tUnit[1] = - tess->tUnit[1];
169 tess->tUnit[2] = - tess->tUnit[2];
173 #ifdef FOR_TRITE_TEST_PROGRAM
175 extern int RandomSweep;
176 #define S_UNIT_X (RandomSweep ? (2*drand48()-1) : 1.0)
177 #define S_UNIT_Y (RandomSweep ? (2*drand48()-1) : 0.0)
179 #if defined(SLANTED_SWEEP)
180 /* The "feature merging" is not intended to be complete. There are
181 * special cases where edges are nearly parallel to the sweep line
182 * which are not implemented. The algorithm should still behave
183 * robustly (ie. produce a reasonable tesselation) in the presence
184 * of such edges, however it may miss features which could have been
185 * merged. We could minimize this effect by choosing the sweep line
186 * direction to be something unusual (ie. not parallel to one of the
189 #define S_UNIT_X 0.50941539564955385 /* Pre-normalized */
190 #define S_UNIT_Y 0.86052074622010633
197 /* Determine the polygon normal and project vertices onto the plane
200 void __gl_projectPolygon( GLUtesselator *tess )
202 GLUvertex *v, *vHead = &tess->mesh->vHead;
204 GLdouble *sUnit, *tUnit;
205 int i, computedNormal = FALSE;
207 norm[0] = tess->normal[0];
208 norm[1] = tess->normal[1];
209 norm[2] = tess->normal[2];
210 if( norm[0] == 0 && norm[1] == 0 && norm[2] == 0 ) {
211 ComputeNormal( tess, norm );
212 computedNormal = TRUE;
216 i = LongAxis( norm );
218 #if defined(FOR_TRITE_TEST_PROGRAM) || defined(TRUE_PROJECT)
219 /* Choose the initial sUnit vector to be approximately perpendicular
225 sUnit[(i+1)%3] = S_UNIT_X;
226 sUnit[(i+2)%3] = S_UNIT_Y;
228 /* Now make it exactly perpendicular */
229 w = Dot( sUnit, norm );
230 sUnit[0] -= w * norm[0];
231 sUnit[1] -= w * norm[1];
232 sUnit[2] -= w * norm[2];
235 /* Choose tUnit so that (sUnit,tUnit,norm) form a right-handed frame */
236 tUnit[0] = norm[1]*sUnit[2] - norm[2]*sUnit[1];
237 tUnit[1] = norm[2]*sUnit[0] - norm[0]*sUnit[2];
238 tUnit[2] = norm[0]*sUnit[1] - norm[1]*sUnit[0];
241 /* Project perpendicular to a coordinate axis -- better numerically */
243 sUnit[(i+1)%3] = S_UNIT_X;
244 sUnit[(i+2)%3] = S_UNIT_Y;
247 tUnit[(i+1)%3] = (norm[i] > 0) ? -S_UNIT_Y : S_UNIT_Y;
248 tUnit[(i+2)%3] = (norm[i] > 0) ? S_UNIT_X : -S_UNIT_X;
251 /* Project the vertices onto the sweep plane */
252 for( v = vHead->next; v != vHead; v = v->next ) {
253 v->s = Dot( v->coords, sUnit );
254 v->t = Dot( v->coords, tUnit );
256 if( computedNormal ) {
257 CheckOrientation( tess );