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Diffstat (limited to 'src/glu/sgi/libtess/geom.c')
| -rw-r--r-- | src/glu/sgi/libtess/geom.c | 271 |
1 files changed, 271 insertions, 0 deletions
diff --git a/src/glu/sgi/libtess/geom.c b/src/glu/sgi/libtess/geom.c new file mode 100644 index 00000000000..cf4305acfae --- /dev/null +++ b/src/glu/sgi/libtess/geom.c @@ -0,0 +1,271 @@ +/* +** 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: 2001/03/17 00:25:41 $ $Revision: 1.1 $ +** $Header: /cvs/mesa/Mesa/src/glu/sgi/libtess/geom.c,v 1.1 2001/03/17 00:25:41 brianp Exp $ +*/ + +#include "gluos.h" +#include <assert.h> +#include "mesh.h" +#include "geom.h" + +int __gl_vertLeq( GLUvertex *u, GLUvertex *v ) +{ + /* Returns TRUE if u is lexicographically <= v. */ + + return VertLeq( u, v ); +} + +GLdouble __gl_edgeEval( GLUvertex *u, GLUvertex *v, GLUvertex *w ) +{ + /* Given three vertices u,v,w such that VertLeq(u,v) && VertLeq(v,w), + * evaluates the t-coord of the edge uw at the s-coord of the vertex v. + * Returns v->t - (uw)(v->s), ie. the signed distance from uw to v. + * If uw is vertical (and thus passes thru v), the result is zero. + * + * The calculation is extremely accurate and stable, even when v + * is very close to u or w. In particular if we set v->t = 0 and + * let r be the negated result (this evaluates (uw)(v->s)), then + * r is guaranteed to satisfy MIN(u->t,w->t) <= r <= MAX(u->t,w->t). + */ + GLdouble gapL, gapR; + + assert( VertLeq( u, v ) && VertLeq( v, w )); + + gapL = v->s - u->s; + gapR = w->s - v->s; + + if( gapL + gapR > 0 ) { + if( gapL < gapR ) { + return (v->t - u->t) + (u->t - w->t) * (gapL / (gapL + gapR)); + } else { + return (v->t - w->t) + (w->t - u->t) * (gapR / (gapL + gapR)); + } + } + /* vertical line */ + return 0; +} + +GLdouble __gl_edgeSign( GLUvertex *u, GLUvertex *v, GLUvertex *w ) +{ + /* Returns a number whose sign matches EdgeEval(u,v,w) but which + * is cheaper to evaluate. Returns > 0, == 0 , or < 0 + * as v is above, on, or below the edge uw. + */ + GLdouble gapL, gapR; + + assert( VertLeq( u, v ) && VertLeq( v, w )); + + gapL = v->s - u->s; + gapR = w->s - v->s; + + if( gapL + gapR > 0 ) { + return (v->t - w->t) * gapL + (v->t - u->t) * gapR; + } + /* vertical line */ + return 0; +} + + +/*********************************************************************** + * Define versions of EdgeSign, EdgeEval with s and t transposed. + */ + +GLdouble __gl_transEval( GLUvertex *u, GLUvertex *v, GLUvertex *w ) +{ + /* Given three vertices u,v,w such that TransLeq(u,v) && TransLeq(v,w), + * evaluates the t-coord of the edge uw at the s-coord of the vertex v. + * Returns v->s - (uw)(v->t), ie. the signed distance from uw to v. + * If uw is vertical (and thus passes thru v), the result is zero. + * + * The calculation is extremely accurate and stable, even when v + * is very close to u or w. In particular if we set v->s = 0 and + * let r be the negated result (this evaluates (uw)(v->t)), then + * r is guaranteed to satisfy MIN(u->s,w->s) <= r <= MAX(u->s,w->s). + */ + GLdouble gapL, gapR; + + assert( TransLeq( u, v ) && TransLeq( v, w )); + + gapL = v->t - u->t; + gapR = w->t - v->t; + + if( gapL + gapR > 0 ) { + if( gapL < gapR ) { + return (v->s - u->s) + (u->s - w->s) * (gapL / (gapL + gapR)); + } else { + return (v->s - w->s) + (w->s - u->s) * (gapR / (gapL + gapR)); + } + } + /* vertical line */ + return 0; +} + +GLdouble __gl_transSign( GLUvertex *u, GLUvertex *v, GLUvertex *w ) +{ + /* Returns a number whose sign matches TransEval(u,v,w) but which + * is cheaper to evaluate. Returns > 0, == 0 , or < 0 + * as v is above, on, or below the edge uw. + */ + GLdouble gapL, gapR; + + assert( TransLeq( u, v ) && TransLeq( v, w )); + + gapL = v->t - u->t; + gapR = w->t - v->t; + + if( gapL + gapR > 0 ) { + return (v->s - w->s) * gapL + (v->s - u->s) * gapR; + } + /* vertical line */ + return 0; +} + + +int __gl_vertCCW( GLUvertex *u, GLUvertex *v, GLUvertex *w ) +{ + /* For almost-degenerate situations, the results are not reliable. + * Unless the floating-point arithmetic can be performed without + * rounding errors, *any* implementation will give incorrect results + * on some degenerate inputs, so the client must have some way to + * handle this situation. + */ + return (u->s*(v->t - w->t) + v->s*(w->t - u->t) + w->s*(u->t - v->t)) >= 0; +} + +/* Given parameters a,x,b,y returns the value (b*x+a*y)/(a+b), + * or (x+y)/2 if a==b==0. It requires that a,b >= 0, and enforces + * this in the rare case that one argument is slightly negative. + * The implementation is extremely stable numerically. + * In particular it guarantees that the result r satisfies + * MIN(x,y) <= r <= MAX(x,y), and the results are very accurate + * even when a and b differ greatly in magnitude. + */ +#define RealInterpolate(a,x,b,y) \ + (a = (a < 0) ? 0 : a, b = (b < 0) ? 0 : b, \ + ((a <= b) ? ((b == 0) ? ((x+y) / 2) \ + : (x + (y-x) * (a/(a+b)))) \ + : (y + (x-y) * (b/(a+b))))) + +#ifndef FOR_TRITE_TEST_PROGRAM +#define Interpolate(a,x,b,y) RealInterpolate(a,x,b,y) +#else + +/* Claim: the ONLY property the sweep algorithm relies on is that + * MIN(x,y) <= r <= MAX(x,y). This is a nasty way to test that. + */ +#include <stdlib.h> +extern int RandomInterpolate; + +GLdouble Interpolate( GLdouble a, GLdouble x, GLdouble b, GLdouble y) +{ +printf("*********************%d\n",RandomInterpolate); + if( RandomInterpolate ) { + a = 1.2 * drand48() - 0.1; + a = (a < 0) ? 0 : ((a > 1) ? 1 : a); + b = 1.0 - a; + } + return RealInterpolate(a,x,b,y); +} + +#endif + +#define Swap(a,b) if (1) { GLUvertex *t = a; a = b; b = t; } else + +void __gl_edgeIntersect( GLUvertex *o1, GLUvertex *d1, + GLUvertex *o2, GLUvertex *d2, + GLUvertex *v ) +/* Given edges (o1,d1) and (o2,d2), compute their point of intersection. + * The computed point is guaranteed to lie in the intersection of the + * bounding rectangles defined by each edge. + */ +{ + GLdouble z1, z2; + + /* This is certainly not the most efficient way to find the intersection + * of two line segments, but it is very numerically stable. + * + * Strategy: find the two middle vertices in the VertLeq ordering, + * and interpolate the intersection s-value from these. Then repeat + * using the TransLeq ordering to find the intersection t-value. + */ + + if( ! VertLeq( o1, d1 )) { Swap( o1, d1 ); } + if( ! VertLeq( o2, d2 )) { Swap( o2, d2 ); } + if( ! VertLeq( o1, o2 )) { Swap( o1, o2 ); Swap( d1, d2 ); } + + if( ! VertLeq( o2, d1 )) { + /* Technically, no intersection -- do our best */ + v->s = (o2->s + d1->s) / 2; + } else if( VertLeq( d1, d2 )) { + /* Interpolate between o2 and d1 */ + z1 = EdgeEval( o1, o2, d1 ); + z2 = EdgeEval( o2, d1, d2 ); + if( z1+z2 < 0 ) { z1 = -z1; z2 = -z2; } + v->s = Interpolate( z1, o2->s, z2, d1->s ); + } else { + /* Interpolate between o2 and d2 */ + z1 = EdgeSign( o1, o2, d1 ); + z2 = -EdgeSign( o1, d2, d1 ); + if( z1+z2 < 0 ) { z1 = -z1; z2 = -z2; } + v->s = Interpolate( z1, o2->s, z2, d2->s ); + } + + /* Now repeat the process for t */ + + if( ! TransLeq( o1, d1 )) { Swap( o1, d1 ); } + if( ! TransLeq( o2, d2 )) { Swap( o2, d2 ); } + if( ! TransLeq( o1, o2 )) { Swap( o1, o2 ); Swap( d1, d2 ); } + + if( ! TransLeq( o2, d1 )) { + /* Technically, no intersection -- do our best */ + v->t = (o2->t + d1->t) / 2; + } else if( TransLeq( d1, d2 )) { + /* Interpolate between o2 and d1 */ + z1 = TransEval( o1, o2, d1 ); + z2 = TransEval( o2, d1, d2 ); + if( z1+z2 < 0 ) { z1 = -z1; z2 = -z2; } + v->t = Interpolate( z1, o2->t, z2, d1->t ); + } else { + /* Interpolate between o2 and d2 */ + z1 = TransSign( o1, o2, d1 ); + z2 = -TransSign( o1, d2, d1 ); + if( z1+z2 < 0 ) { z1 = -z1; z2 = -z2; } + v->t = Interpolate( z1, o2->t, z2, d2->t ); + } +} |