path: root/src/classes/com/sun/opengl/impl/tessellator/Render.java

/*
* 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 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.
**
** 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.sun.opengl.impl.glu.tessellator;

import javax.media.opengl.*;
import javax.media.opengl.glu.*;

class Render {
    private static final boolean USE_OPTIMIZED_CODE_PATH = false;

    private Render() {
    }

    private static final RenderFan renderFan = new RenderFan();
    private static final RenderStrip renderStrip = new RenderStrip();
    private static final RenderTriangle renderTriangle = new RenderTriangle();

/* This structure remembers the information we need about a primitive
 * to be able to render it later, once we have determined which
 * primitive is able to use the most triangles.
 */
    private static class FaceCount {
        public FaceCount() {
        }

        public FaceCount(long size, com.sun.opengl.impl.glu.tessellator.GLUhalfEdge eStart, renderCallBack render) {
            this.size = size;
            this.eStart = eStart;
            this.render = render;
        }

        long size;		/* number of triangles used */
        com.sun.opengl.impl.glu.tessellator.GLUhalfEdge eStart;	/* edge where this primitive starts */
        renderCallBack render;
    };

    private static interface renderCallBack {
        void render(GLUtessellatorImpl tess, com.sun.opengl.impl.glu.tessellator.GLUhalfEdge e, long size);
    }

    /************************ Strips and Fans decomposition ******************/

/* __gl_renderMesh( tess, mesh ) takes a mesh and breaks it into triangle
 * fans, strips, and separate triangles.  A substantial effort is made
 * to use as few rendering primitives as possible (ie. to make the fans
 * and strips as large as possible).
 *
 * The rendering output is provided as callbacks (see the api).
 */
    public static void __gl_renderMesh(GLUtessellatorImpl tess, com.sun.opengl.impl.glu.tessellator.GLUmesh mesh) {
        com.sun.opengl.impl.glu.tessellator.GLUface f;

        /* Make a list of separate triangles so we can render them all at once */
        tess.lonelyTriList = null;

        for (f = mesh.fHead.next; f != mesh.fHead; f = f.next) {
            f.marked = false;
        }
        for (f = mesh.fHead.next; f != mesh.fHead; f = f.next) {

            /* We examine all faces in an arbitrary order.  Whenever we find
             * an unprocessed face F, we output a group of faces including F
             * whose size is maximum.
             */
            if (f.inside && !f.marked) {
                RenderMaximumFaceGroup(tess, f);
                assert (f.marked);
            }
        }
        if (tess.lonelyTriList != null) {
            RenderLonelyTriangles(tess, tess.lonelyTriList);
            tess.lonelyTriList = null;
        }
    }


    static void RenderMaximumFaceGroup(GLUtessellatorImpl tess, com.sun.opengl.impl.glu.tessellator.GLUface fOrig) {
        /* We want to find the largest triangle fan or strip of unmarked faces
         * which includes the given face fOrig.  There are 3 possible fans
         * passing through fOrig (one centered at each vertex), and 3 possible
         * strips (one for each CCW permutation of the vertices).  Our strategy
         * is to try all of these, and take the primitive which uses the most
         * triangles (a greedy approach).
         */
        com.sun.opengl.impl.glu.tessellator.GLUhalfEdge e = fOrig.anEdge;
        FaceCount max = new FaceCount();
        FaceCount newFace = new FaceCount();

        max.size = 1;
        max.eStart = e;
        max.render = renderTriangle;

        if (!tess.flagBoundary) {
            newFace = MaximumFan(e);
            if (newFace.size > max.size) {
                max = newFace;
            }
            newFace = MaximumFan(e.Lnext);
            if (newFace.size > max.size) {
                max = newFace;
            }
            newFace = MaximumFan(e.Onext.Sym);
            if (newFace.size > max.size) {
                max = newFace;
            }

            newFace = MaximumStrip(e);
            if (newFace.size > max.size) {
                max = newFace;
            }
            newFace = MaximumStrip(e.Lnext);
            if (newFace.size > max.size) {
                max = newFace;
            }
            newFace = MaximumStrip(e.Onext.Sym);
            if (newFace.size > max.size) {
                max = newFace;
            }
        }
        max.render.render(tess, max.eStart, max.size);
    }


/* Macros which keep track of faces we have marked temporarily, and allow
 * us to backtrack when necessary.  With triangle fans, this is not
 * really necessary, since the only awkward case is a loop of triangles
 * around a single origin vertex.  However with strips the situation is
 * more complicated, and we need a general tracking method like the
 * one here.
 */
    private static boolean Marked(com.sun.opengl.impl.glu.tessellator.GLUface f) {
        return !f.inside || f.marked;
    }

    private static GLUface AddToTrail(com.sun.opengl.impl.glu.tessellator.GLUface f, com.sun.opengl.impl.glu.tessellator.GLUface t) {
        f.trail = t;
        f.marked = true;
        return f;
    }

    private static void FreeTrail(com.sun.opengl.impl.glu.tessellator.GLUface t) {
        if (true) {
            while (t != null) {
                t.marked = false;
                t = t.trail;
            }
        } else {
            /* absorb trailing semicolon */
        }
    }

    static FaceCount MaximumFan(com.sun.opengl.impl.glu.tessellator.GLUhalfEdge eOrig) {
        /* eOrig.Lface is the face we want to render.  We want to find the size
         * of a maximal fan around eOrig.Org.  To do this we just walk around
         * the origin vertex as far as possible in both directions.
         */
        FaceCount newFace = new FaceCount(0, null, renderFan);
        com.sun.opengl.impl.glu.tessellator.GLUface trail = null;
        com.sun.opengl.impl.glu.tessellator.GLUhalfEdge e;

        for (e = eOrig; !Marked(e.Lface); e = e.Onext) {
            trail = AddToTrail(e.Lface, trail);
            ++newFace.size;
        }
        for (e = eOrig; !Marked(e.Sym.Lface); e = e.Sym.Lnext) {
            trail = AddToTrail(e.Sym.Lface, trail);
            ++newFace.size;
        }
        newFace.eStart = e;
        /*LINTED*/
        FreeTrail(trail);
        return newFace;
    }


    private static boolean IsEven(long n) {
        return (n & 0x1L) == 0;
    }

    static FaceCount MaximumStrip(com.sun.opengl.impl.glu.tessellator.GLUhalfEdge eOrig) {
        /* Here we are looking for a maximal strip that contains the vertices
         * eOrig.Org, eOrig.Dst, eOrig.Lnext.Dst (in that order or the
         * reverse, such that all triangles are oriented CCW).
         *
         * Again we walk forward and backward as far as possible.  However for
         * strips there is a twist: to get CCW orientations, there must be
         * an *even* number of triangles in the strip on one side of eOrig.
         * We walk the strip starting on a side with an even number of triangles;
         * if both side have an odd number, we are forced to shorten one side.
         */
        FaceCount newFace = new FaceCount(0, null, renderStrip);
        long headSize = 0, tailSize = 0;
        com.sun.opengl.impl.glu.tessellator.GLUface trail = null;
        com.sun.opengl.impl.glu.tessellator.GLUhalfEdge e, eTail, eHead;

        for (e = eOrig; !Marked(e.Lface); ++tailSize, e = e.Onext) {
            trail = AddToTrail(e.Lface, trail);
            ++tailSize;
            e = e.Lnext.Sym;
            if (Marked(e.Lface)) break;
            trail = AddToTrail(e.Lface, trail);
        }
        eTail = e;

        for (e = eOrig; !Marked(e.Sym.Lface); ++headSize, e = e.Sym.Onext.Sym) {
            trail = AddToTrail(e.Sym.Lface, trail);
            ++headSize;
            e = e.Sym.Lnext;
            if (Marked(e.Sym.Lface)) break;
            trail = AddToTrail(e.Sym.Lface, trail);
        }
        eHead = e;

        newFace.size = tailSize + headSize;
        if (IsEven(tailSize)) {
            newFace.eStart = eTail.Sym;
        } else if (IsEven(headSize)) {
            newFace.eStart = eHead;
        } else {
            /* Both sides have odd length, we must shorten one of them.  In fact,
             * we must start from eHead to guarantee inclusion of eOrig.Lface.
             */
            --newFace.size;
            newFace.eStart = eHead.Onext;
        }
        /*LINTED*/
        FreeTrail(trail);
        return newFace;
    }

    private static class RenderTriangle implements renderCallBack {
        public void render(GLUtessellatorImpl tess, com.sun.opengl.impl.glu.tessellator.GLUhalfEdge e, long size) {
            /* Just add the triangle to a triangle list, so we can render all
             * the separate triangles at once.
             */
            assert (size == 1);
            tess.lonelyTriList = AddToTrail(e.Lface, tess.lonelyTriList);
        }
    }


    static void RenderLonelyTriangles(GLUtessellatorImpl tess, com.sun.opengl.impl.glu.tessellator.GLUface f) {
        /* Now we render all the separate triangles which could not be
         * grouped into a triangle fan or strip.
         */
        com.sun.opengl.impl.glu.tessellator.GLUhalfEdge e;
        int newState;
        int edgeState = -1;	/* force edge state output for first vertex */

        tess.callBeginOrBeginData(GL2ES1.GL_TRIANGLES);

        for (; f != null; f = f.trail) {
            /* Loop once for each edge (there will always be 3 edges) */

            e = f.anEdge;
            do {
                if (tess.flagBoundary) {
                    /* Set the "edge state" to true just before we output the
                     * first vertex of each edge on the polygon boundary.
                     */
                    newState = (!e.Sym.Lface.inside) ? 1 : 0;
                    if (edgeState != newState) {
                        edgeState = newState;
                        tess.callEdgeFlagOrEdgeFlagData( edgeState != 0);
                    }
                }
                tess.callVertexOrVertexData( e.Org.data);

                e = e.Lnext;
            } while (e != f.anEdge);
        }
        tess.callEndOrEndData();
    }

    private static class RenderFan implements renderCallBack {
        public void render(GLUtessellatorImpl tess, com.sun.opengl.impl.glu.tessellator.GLUhalfEdge e, long size) {
            /* Render as many CCW triangles as possible in a fan starting from
             * edge "e".  The fan *should* contain exactly "size" triangles
             * (otherwise we've goofed up somewhere).
             */
            tess.callBeginOrBeginData( GL2ES1.GL_TRIANGLE_FAN);
            tess.callVertexOrVertexData( e.Org.data);
            tess.callVertexOrVertexData( e.Sym.Org.data);

            while (!Marked(e.Lface)) {
                e.Lface.marked = true;
                --size;
                e = e.Onext;
                tess.callVertexOrVertexData( e.Sym.Org.data);
            }

            assert (size == 0);
            tess.callEndOrEndData();
        }
    }

    private static class RenderStrip implements renderCallBack {
        public void render(GLUtessellatorImpl tess, com.sun.opengl.impl.glu.tessellator.GLUhalfEdge e, long size) {
            /* Render as many CCW triangles as possible in a strip starting from
             * edge "e".  The strip *should* contain exactly "size" triangles
             * (otherwise we've goofed up somewhere).
             */
            tess.callBeginOrBeginData( GL2ES1.GL_TRIANGLE_STRIP);
            tess.callVertexOrVertexData( e.Org.data);
            tess.callVertexOrVertexData( e.Sym.Org.data);

            while (!Marked(e.Lface)) {
                e.Lface.marked = true;
                --size;
                e = e.Lnext.Sym;
                tess.callVertexOrVertexData( e.Org.data);
                if (Marked(e.Lface)) break;

                e.Lface.marked = true;
                --size;
                e = e.Onext;
                tess.callVertexOrVertexData( e.Sym.Org.data);
            }

            assert (size == 0);
            tess.callEndOrEndData();
        }
    }

    /************************ Boundary contour decomposition ******************/

/* __gl_renderBoundary( tess, mesh ) takes a mesh, and outputs one
 * contour for each face marked "inside".  The rendering output is
 * provided as callbacks (see the api).
 */
    public static void __gl_renderBoundary(GLUtessellatorImpl tess, com.sun.opengl.impl.glu.tessellator.GLUmesh mesh) {
        com.sun.opengl.impl.glu.tessellator.GLUface f;
        com.sun.opengl.impl.glu.tessellator.GLUhalfEdge e;

        for (f = mesh.fHead.next; f != mesh.fHead; f = f.next) {
            if (f.inside) {
                tess.callBeginOrBeginData( GL2ES1.GL_LINE_LOOP);
                e = f.anEdge;
                do {
                    tess.callVertexOrVertexData( e.Org.data);
                    e = e.Lnext;
                } while (e != f.anEdge);
                tess.callEndOrEndData();
            }
        }
    }


    /************************ Quick-and-dirty decomposition ******************/

    private static final int SIGN_INCONSISTENT = 2;

    static int ComputeNormal(GLUtessellatorImpl tess, double[] norm, boolean check)
/*
 * If check==false, we compute the polygon normal and place it in norm[].
 * If check==true, we check that each triangle in the fan from v0 has a
 * consistent orientation with respect to norm[].  If triangles are
 * consistently oriented CCW, return 1; if CW, return -1; if all triangles
 * are degenerate return 0; otherwise (no consistent orientation) return
 * SIGN_INCONSISTENT.
 */ {
        com.sun.opengl.impl.glu.tessellator.CachedVertex[] v = tess.cache;
//            CachedVertex vn = v0 + tess.cacheCount;
        int vn = tess.cacheCount;
//            CachedVertex vc;
        int vc;
        double dot, xc, yc, zc, xp, yp, zp;
        double[] n = new double[3];
        int sign = 0;

        /* Find the polygon normal.  It is important to get a reasonable
         * normal even when the polygon is self-intersecting (eg. a bowtie).
         * Otherwise, the computed normal could be very tiny, but perpendicular
         * to the true plane of the polygon due to numerical noise.  Then all
         * the triangles would appear to be degenerate and we would incorrectly
         * decompose the polygon as a fan (or simply not render it at all).
         *
         * We use a sum-of-triangles normal algorithm rather than the more
         * efficient sum-of-trapezoids method (used in CheckOrientation()
         * in normal.c).  This lets us explicitly reverse the signed area
         * of some triangles to get a reasonable normal in the self-intersecting
         * case.
         */
        if (!check) {
            norm[0] = norm[1] = norm[2] = 0.0;
        }

        vc = 1;
        xc = v[vc].coords[0] - v[0].coords[0];
        yc = v[vc].coords[1] - v[0].coords[1];
        zc = v[vc].coords[2] - v[0].coords[2];
        while (++vc < vn) {
            xp = xc;
            yp = yc;
            zp = zc;
            xc = v[vc].coords[0] - v[0].coords[0];
            yc = v[vc].coords[1] - v[0].coords[1];
            zc = v[vc].coords[2] - v[0].coords[2];

            /* Compute (vp - v0) cross (vc - v0) */
            n[0] = yp * zc - zp * yc;
            n[1] = zp * xc - xp * zc;
            n[2] = xp * yc - yp * xc;

            dot = n[0] * norm[0] + n[1] * norm[1] + n[2] * norm[2];
            if (!check) {
                /* Reverse the contribution of back-facing triangles to get
                 * a reasonable normal for self-intersecting polygons (see above)
                 */
                if (dot >= 0) {
                    norm[0] += n[0];
                    norm[1] += n[1];
                    norm[2] += n[2];
                } else {
                    norm[0] -= n[0];
                    norm[1] -= n[1];
                    norm[2] -= n[2];
                }
            } else if (dot != 0) {
                /* Check the new orientation for consistency with previous triangles */
                if (dot > 0) {
                    if (sign < 0) return SIGN_INCONSISTENT;
                    sign = 1;
                } else {
                    if (sign > 0) return SIGN_INCONSISTENT;
                    sign = -1;
                }
            }
        }
        return sign;
    }

/* __gl_renderCache( tess ) takes a single contour and tries to render it
 * as a triangle fan.  This handles convex polygons, as well as some
 * non-convex polygons if we get lucky.
 *
 * Returns true if the polygon was successfully rendered.  The rendering
 * output is provided as callbacks (see the api).
 */
    public static boolean __gl_renderCache(GLUtessellatorImpl tess) {
        com.sun.opengl.impl.glu.tessellator.CachedVertex[] v = tess.cache;
//            CachedVertex vn = v0 + tess.cacheCount;
        int vn = tess.cacheCount;
//            CachedVertex vc;
        int vc;
        double[] norm = new double[3];
        int sign;

        if (tess.cacheCount < 3) {
            /* Degenerate contour -- no output */
            return true;
        }

        norm[0] = tess.normal[0];
        norm[1] = tess.normal[1];
        norm[2] = tess.normal[2];
        if (norm[0] == 0 && norm[1] == 0 && norm[2] == 0) {
            ComputeNormal( tess, norm, false);
        }

        sign = ComputeNormal( tess, norm, true);
        if (sign == SIGN_INCONSISTENT) {
            /* Fan triangles did not have a consistent orientation */
            return false;
        }
        if (sign == 0) {
            /* All triangles were degenerate */
            return true;
        }

        if ( !USE_OPTIMIZED_CODE_PATH ) {
            return false;
        } else {
            /* Make sure we do the right thing for each winding rule */
            switch (tess.windingRule) {
                case GLU.GLU_TESS_WINDING_ODD:
                case GLU.GLU_TESS_WINDING_NONZERO:
                    break;
                case GLU.GLU_TESS_WINDING_POSITIVE:
                    if (sign < 0) return true;
                    break;
                case GLU.GLU_TESS_WINDING_NEGATIVE:
                    if (sign > 0) return true;
                    break;
                case GLU.GLU_TESS_WINDING_ABS_GEQ_TWO:
                    return true;
            }

            tess.callBeginOrBeginData( tess.boundaryOnly ? GL2ES1.GL_LINE_LOOP
                    : (tess.cacheCount > 3) ? GL2ES1.GL_TRIANGLE_FAN
                    : GL2ES1.GL_TRIANGLES);

            tess.callVertexOrVertexData( v[0].data);
            if (sign > 0) {
                for (vc = 1; vc < vn; ++vc) {
                    tess.callVertexOrVertexData( v[vc].data);
                }
            } else {
                for (vc = vn - 1; vc > 0; --vc) {
                    tess.callVertexOrVertexData( v[vc].data);
                }
            }
            tess.callEndOrEndData();
            return true;
        }
    }
}