201 lines
7.1 KiB
C
201 lines
7.1 KiB
C
/*
|
|
* SGI FREE SOFTWARE LICENSE B (Version 2.0, Sept. 18, 2008)
|
|
* Copyright (C) 1991-2000 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 "gluos.h"
|
|
#include <stdlib.h>
|
|
#include "geom.h"
|
|
#include "mesh.h"
|
|
#include "tessmono.h"
|
|
#include <assert.h>
|
|
|
|
#define AddWinding(eDst,eSrc) (eDst->winding += eSrc->winding, \
|
|
eDst->Sym->winding += eSrc->Sym->winding)
|
|
|
|
/* __gl_meshTessellateMonoRegion( face ) tessellates a monotone region
|
|
* (what else would it do??) The region must consist of a single
|
|
* loop of half-edges (see mesh.h) oriented CCW. "Monotone" in this
|
|
* case means that any vertical line intersects the interior of the
|
|
* region in a single interval.
|
|
*
|
|
* Tessellation consists of adding interior edges (actually pairs of
|
|
* half-edges), to split the region into non-overlapping triangles.
|
|
*
|
|
* The basic idea is explained in Preparata and Shamos (which I don''t
|
|
* have handy right now), although their implementation is more
|
|
* complicated than this one. The are two edge chains, an upper chain
|
|
* and a lower chain. We process all vertices from both chains in order,
|
|
* from right to left.
|
|
*
|
|
* The algorithm ensures that the following invariant holds after each
|
|
* vertex is processed: the untessellated region consists of two
|
|
* chains, where one chain (say the upper) is a single edge, and
|
|
* the other chain is concave. The left vertex of the single edge
|
|
* is always to the left of all vertices in the concave chain.
|
|
*
|
|
* Each step consists of adding the rightmost unprocessed vertex to one
|
|
* of the two chains, and forming a fan of triangles from the rightmost
|
|
* of two chain endpoints. Determining whether we can add each triangle
|
|
* to the fan is a simple orientation test. By making the fan as large
|
|
* as possible, we restore the invariant (check it yourself).
|
|
*/
|
|
int __gl_meshTessellateMonoRegion( GLUface *face )
|
|
{
|
|
GLUhalfEdge *up, *lo;
|
|
|
|
/* All edges are oriented CCW around the boundary of the region.
|
|
* First, find the half-edge whose origin vertex is rightmost.
|
|
* Since the sweep goes from left to right, face->anEdge should
|
|
* be close to the edge we want.
|
|
*/
|
|
up = face->anEdge;
|
|
assert( up->Lnext != up && up->Lnext->Lnext != up );
|
|
|
|
for( ; VertLeq( up->Dst, up->Org ); up = up->Lprev )
|
|
;
|
|
for( ; VertLeq( up->Org, up->Dst ); up = up->Lnext )
|
|
;
|
|
lo = up->Lprev;
|
|
|
|
while( up->Lnext != lo ) {
|
|
if( VertLeq( up->Dst, lo->Org )) {
|
|
/* up->Dst is on the left. It is safe to form triangles from lo->Org.
|
|
* The EdgeGoesLeft test guarantees progress even when some triangles
|
|
* are CW, given that the upper and lower chains are truly monotone.
|
|
*/
|
|
while( lo->Lnext != up && (EdgeGoesLeft( lo->Lnext )
|
|
|| EdgeSign( lo->Org, lo->Dst, lo->Lnext->Dst ) <= 0 )) {
|
|
GLUhalfEdge *tempHalfEdge= __gl_meshConnect( lo->Lnext, lo );
|
|
if (tempHalfEdge == NULL) return 0;
|
|
lo = tempHalfEdge->Sym;
|
|
}
|
|
lo = lo->Lprev;
|
|
} else {
|
|
/* lo->Org is on the left. We can make CCW triangles from up->Dst. */
|
|
while( lo->Lnext != up && (EdgeGoesRight( up->Lprev )
|
|
|| EdgeSign( up->Dst, up->Org, up->Lprev->Org ) >= 0 )) {
|
|
GLUhalfEdge *tempHalfEdge= __gl_meshConnect( up, up->Lprev );
|
|
if (tempHalfEdge == NULL) return 0;
|
|
up = tempHalfEdge->Sym;
|
|
}
|
|
up = up->Lnext;
|
|
}
|
|
}
|
|
|
|
/* Now lo->Org == up->Dst == the leftmost vertex. The remaining region
|
|
* can be tessellated in a fan from this leftmost vertex.
|
|
*/
|
|
assert( lo->Lnext != up );
|
|
while( lo->Lnext->Lnext != up ) {
|
|
GLUhalfEdge *tempHalfEdge= __gl_meshConnect( lo->Lnext, lo );
|
|
if (tempHalfEdge == NULL) return 0;
|
|
lo = tempHalfEdge->Sym;
|
|
}
|
|
|
|
return 1;
|
|
}
|
|
|
|
|
|
/* __gl_meshTessellateInterior( mesh ) tessellates each region of
|
|
* the mesh which is marked "inside" the polygon. Each such region
|
|
* must be monotone.
|
|
*/
|
|
int __gl_meshTessellateInterior( GLUmesh *mesh )
|
|
{
|
|
GLUface *f, *next;
|
|
|
|
/*LINTED*/
|
|
for( f = mesh->fHead.next; f != &mesh->fHead; f = next ) {
|
|
/* Make sure we don''t try to tessellate the new triangles. */
|
|
next = f->next;
|
|
if( f->inside ) {
|
|
if ( !__gl_meshTessellateMonoRegion( f ) ) return 0;
|
|
}
|
|
}
|
|
|
|
return 1;
|
|
}
|
|
|
|
|
|
/* __gl_meshDiscardExterior( mesh ) zaps (ie. sets to NULL) all faces
|
|
* which are not marked "inside" the polygon. Since further mesh operations
|
|
* on NULL faces are not allowed, the main purpose is to clean up the
|
|
* mesh so that exterior loops are not represented in the data structure.
|
|
*/
|
|
void __gl_meshDiscardExterior( GLUmesh *mesh )
|
|
{
|
|
GLUface *f, *next;
|
|
|
|
/*LINTED*/
|
|
for( f = mesh->fHead.next; f != &mesh->fHead; f = next ) {
|
|
/* Since f will be destroyed, save its next pointer. */
|
|
next = f->next;
|
|
if( ! f->inside ) {
|
|
__gl_meshZapFace( f );
|
|
}
|
|
}
|
|
}
|
|
|
|
#define MARKED_FOR_DELETION 0x7fffffff
|
|
|
|
/* __gl_meshSetWindingNumber( mesh, value, keepOnlyBoundary ) resets the
|
|
* winding numbers on all edges so that regions marked "inside" the
|
|
* polygon have a winding number of "value", and regions outside
|
|
* have a winding number of 0.
|
|
*
|
|
* If keepOnlyBoundary is TRUE, it also deletes all edges which do not
|
|
* separate an interior region from an exterior one.
|
|
*/
|
|
int __gl_meshSetWindingNumber( GLUmesh *mesh, int value,
|
|
GLboolean keepOnlyBoundary )
|
|
{
|
|
GLUhalfEdge *e, *eNext;
|
|
|
|
for( e = mesh->eHead.next; e != &mesh->eHead; e = eNext ) {
|
|
eNext = e->next;
|
|
if( e->Rface->inside != e->Lface->inside ) {
|
|
|
|
/* This is a boundary edge (one side is interior, one is exterior). */
|
|
e->winding = (e->Lface->inside) ? value : -value;
|
|
} else {
|
|
|
|
/* Both regions are interior, or both are exterior. */
|
|
if( ! keepOnlyBoundary ) {
|
|
e->winding = 0;
|
|
} else {
|
|
if ( !__gl_meshDelete( e ) ) return 0;
|
|
}
|
|
}
|
|
}
|
|
return 1;
|
|
}
|