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/* * Portions Copyright (C) 2003-2006 Sun Microsystems, Inc. * All rights reserved.// ww w . j a va 2 s . c o m */ /* ** 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 ** Processing integration: Andres Colubri, February 2012 */ package com.processing.opengl.tess; 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; } }