add tessellation library

1 files changed, 261 insertions, 0 deletions

diff --git a/src/libtess2/geom.c b/src/libtess2/geom.c
new file mode 100755
index 0000000000..44cf38c1df
--- /dev/null
+++ b/src/libtess2/geom.c
@@ -0,0 +1,261 @@
+/*
+** SGI FREE SOFTWARE LICENSE B (Version 2.0, Sept. 18, 2008)
+** Copyright (C) [dates of first publication] Silicon Graphics, Inc.
+** All Rights Reserved.
+**
+** Permission is hereby granted, free of charge, to any person obtaining a copy
+** of this software and associated documentation files (the "Software"), to deal
+** in the Software without restriction, including without limitation the rights
+** to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+** of the Software, and to permit persons to whom the Software is furnished to do so,
+** subject to the following conditions:
+**
+** The above copyright notice including the dates of first publication and either this
+** permission notice or a reference to http://oss.sgi.com/projects/FreeB/ shall be
+** included in all copies or substantial portions of the Software.
+**
+** THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+** INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+** PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL SILICON GRAPHICS, INC.
+** BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+** TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
+** OR OTHER DEALINGS IN THE SOFTWARE.
+**
+** Except as contained in this notice, the name of Silicon Graphics, Inc. shall not
+** be used in advertising or otherwise to promote the sale, use or other dealings in
+** this Software without prior written authorization from Silicon Graphics, Inc.
+*/
+/*
+** Author: Eric Veach, July 1994.
+*/
+
+//#include "tesos.h"
+#include <assert.h>
+#include "mesh.h"
+#include "geom.h"
+
+int tesvertLeq( TESSvertex *u, TESSvertex *v )
+{
+	/* Returns TRUE if u is lexicographically <= v. */
+
+	return VertLeq( u, v );
+}
+
+TESSreal tesedgeEval( TESSvertex *u, TESSvertex *v, TESSvertex *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).
+	*/
+	TESSreal 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;
+}
+
+TESSreal tesedgeSign( TESSvertex *u, TESSvertex *v, TESSvertex *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.
+	*/
+	TESSreal 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.
+*/
+
+TESSreal testransEval( TESSvertex *u, TESSvertex *v, TESSvertex *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).
+	*/
+	TESSreal 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;
+}
+
+TESSreal testransSign( TESSvertex *u, TESSvertex *v, TESSvertex *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.
+	*/
+	TESSreal 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 tesvertCCW( TESSvertex *u, TESSvertex *v, TESSvertex *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;
+
+double Interpolate( double a, double x, double b, double 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) { TESSvertex *t = a; a = b; b = t; } else
+
+void tesedgeIntersect( TESSvertex *o1, TESSvertex *d1,
+					  TESSvertex *o2, TESSvertex *d2,
+					  TESSvertex *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.
+					  */
+{
+	TESSreal 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 );
+	}
+}