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Diffstat (limited to 'libtess/normal.c')
| -rw-r--r-- | libtess/normal.c | 259 |
1 files changed, 259 insertions, 0 deletions
diff --git a/libtess/normal.c b/libtess/normal.c new file mode 100644 index 0000000..feae622 --- /dev/null +++ b/libtess/normal.c @@ -0,0 +1,259 @@ +/* +** 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. +** +** $Date$ $Revision$ +** $Header$ +*/ + +#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 + +#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 ); + } +} |