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/*
* Portions Copyright (C) 2003-2006 Sun Microsystems, Inc.
* All rights reserved.
*/
/*
** 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 2.0 (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.
**
** NOTE: The Original Code (as defined below) has been licensed to Sun
** Microsystems, Inc. ("Sun") under the SGI Free Software License B
** (Version 1.1), shown above ("SGI License"). Pursuant to Section
** 3.2(3) of the SGI License, Sun is distributing the Covered Code to
** you under an alternative license ("Alternative License"). This
** Alternative License includes all of the provisions of the SGI License
** except that Section 2.2 and 11 are omitted. Any differences between
** the Alternative License and the SGI License are offered solely by Sun
** and not by SGI.
**
** 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
** Java Port: Pepijn Van Eeckhoudt, July 2003
** Java Port: Nathan Parker Burg, August 2003
*/
package com.jogamp.opengl.impl.glu.tessellator;
class TessMono {
/* __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).
*/
static boolean __gl_meshTessellateMonoRegion(GLUface face, boolean avoidDegenerateTris) {
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 (; Geom.VertLeq(up.Sym.Org, up.Org); up = up.Onext.Sym)
;
for (; Geom.VertLeq(up.Org, up.Sym.Org); up = up.Lnext)
;
lo = up.Onext.Sym;
boolean mustConnect = false; // hack for avoidDegenerateTris
while (up.Lnext != lo) {
if (avoidDegenerateTris && !mustConnect) {
// Skip over regions where several vertices are collinear,
// to try to avoid producing degenerate (zero-area) triangles
//
// The "mustConnect" flag is a hack to try to avoid
// skipping too large regions and causing incorrect
// triangulations. This entire modification is overall
// not robust and needs more work
if (Geom.EdgeCos(lo.Lnext.Org, lo.Org, lo.Lnext.Lnext.Org) <= -Geom.ONE_MINUS_EPSILON) {
// Lines around lo
do {
lo = lo.Onext.Sym;
mustConnect = true;
} while (up.Lnext != lo &&
Geom.EdgeCos(lo.Lnext.Org, lo.Org, lo.Lnext.Lnext.Org) <= -Geom.ONE_MINUS_EPSILON);
} else if (Geom.EdgeCos(up.Onext.Sym.Org, up.Org, up.Onext.Sym.Onext.Sym.Org) <= -Geom.ONE_MINUS_EPSILON) {
// Lines around up
do {
up = up.Lnext;
mustConnect = true;
} while (up.Lnext != lo &&
Geom.EdgeCos(up.Onext.Sym.Org, up.Org, up.Onext.Sym.Onext.Sym.Org) <= -Geom.ONE_MINUS_EPSILON);
}
if (up.Lnext == lo)
break;
}
if (Geom.VertLeq(up.Sym.Org, lo.Org)) {
/* up.Sym.Org 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 && (Geom.EdgeGoesLeft(lo.Lnext)
|| Geom.EdgeSign(lo.Org, lo.Sym.Org, lo.Lnext.Sym.Org) <= 0)) {
GLUhalfEdge tempHalfEdge = Mesh.__gl_meshConnect(lo.Lnext, lo);
mustConnect = false;
if (tempHalfEdge == null) return false;
lo = tempHalfEdge.Sym;
}
lo = lo.Onext.Sym;
} else {
/* lo.Org is on the left. We can make CCW triangles from up.Sym.Org. */
while (lo.Lnext != up && (Geom.EdgeGoesRight(up.Onext.Sym)
|| Geom.EdgeSign(up.Sym.Org, up.Org, up.Onext.Sym.Org) >= 0)) {
GLUhalfEdge tempHalfEdge = Mesh.__gl_meshConnect(up, up.Onext.Sym);
mustConnect = false;
if (tempHalfEdge == null) return false;
up = tempHalfEdge.Sym;
}
up = up.Lnext;
}
}
/* Now lo.Org == up.Sym.Org == 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 = Mesh.__gl_meshConnect(lo.Lnext, lo);
if (tempHalfEdge == null) return false;
lo = tempHalfEdge.Sym;
}
return true;
}
/* __gl_meshTessellateInterior( mesh ) tessellates each region of
* the mesh which is marked "inside" the polygon. Each such region
* must be monotone.
*/
public static boolean __gl_meshTessellateInterior(GLUmesh mesh, boolean avoidDegenerateTris) {
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, avoidDegenerateTris)) return false;
}
}
return true;
}
/* __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.
*/
public static 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) {
Mesh.__gl_meshZapFace(f);
}
}
}
private static final int 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.
*/
public static boolean __gl_meshSetWindingNumber(GLUmesh mesh, int value, boolean keepOnlyBoundary) {
GLUhalfEdge e, eNext;
for (e = mesh.eHead.next; e != mesh.eHead; e = eNext) {
eNext = e.next;
if (e.Sym.Lface.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 (!Mesh.__gl_meshDelete(e)) return false;
}
}
}
return true;
}
}
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