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Diffstat (limited to 'libtess/render.c')
| -rw-r--r-- | libtess/render.c | 505 |
1 files changed, 505 insertions, 0 deletions
diff --git a/libtess/render.c b/libtess/render.c new file mode 100644 index 0000000..7434b03 --- /dev/null +++ b/libtess/render.c @@ -0,0 +1,505 @@ +/* +** 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. +** +** 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. +** +** $Date$ $Revision$ +** $Header$ +*/ + +#include "gluos.h" +#include <assert.h> +#include <stddef.h> +#include "mesh.h" +#include "tess.h" +#include "render.h" + +#define TRUE 1 +#define FALSE 0 + +/* 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. + */ +struct FaceCount { + long size; /* number of triangles used */ + GLUhalfEdge *eStart; /* edge where this primitive starts */ + void (*render)(GLUtesselator *, GLUhalfEdge *, long); + /* routine to render this primitive */ +}; + +static struct FaceCount MaximumFan( GLUhalfEdge *eOrig ); +static struct FaceCount MaximumStrip( GLUhalfEdge *eOrig ); + +static void RenderFan( GLUtesselator *tess, GLUhalfEdge *eStart, long size ); +static void RenderStrip( GLUtesselator *tess, GLUhalfEdge *eStart, long size ); +static void RenderTriangle( GLUtesselator *tess, GLUhalfEdge *eStart, + long size ); + +static void RenderMaximumFaceGroup( GLUtesselator *tess, GLUface *fOrig ); +static void RenderLonelyTriangles( GLUtesselator *tess, GLUface *head ); + + + +/************************ 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). + */ +void __gl_renderMesh( GLUtesselator *tess, GLUmesh *mesh ) +{ + 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( GLUtesselator *tess, 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). + */ + GLUhalfEdge *e = fOrig->anEdge; + struct FaceCount max, newFace; + + 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->Lprev ); 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->Lprev ); if( newFace.size > max.size ) { max = newFace; } + } + (*(max.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. + */ +#define Marked(f) (! (f)->inside || (f)->marked) + +#define AddToTrail(f,t) ((f)->trail = (t), (t) = (f), (f)->marked = TRUE) + +#define FreeTrail(t) if( 1 ) { \ + while( (t) != NULL ) { \ + (t)->marked = FALSE; t = (t)->trail; \ + } \ + } else /* absorb trailing semicolon */ + + + +static struct FaceCount MaximumFan( 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. + */ + struct FaceCount newFace = { 0, NULL, &RenderFan }; + GLUface *trail = NULL; + GLUhalfEdge *e; + + for( e = eOrig; ! Marked( e->Lface ); e = e->Onext ) { + AddToTrail( e->Lface, trail ); + ++newFace.size; + } + for( e = eOrig; ! Marked( e->Rface ); e = e->Oprev ) { + AddToTrail( e->Rface, trail ); + ++newFace.size; + } + newFace.eStart = e; + /*LINTED*/ + FreeTrail( trail ); + return newFace; +} + + +#define IsEven(n) (((n) & 1) == 0) + +static struct FaceCount MaximumStrip( 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. + */ + struct FaceCount newFace = { 0, NULL, &RenderStrip }; + long headSize = 0, tailSize = 0; + GLUface *trail = NULL; + GLUhalfEdge *e, *eTail, *eHead; + + for( e = eOrig; ! Marked( e->Lface ); ++tailSize, e = e->Onext ) { + AddToTrail( e->Lface, trail ); + ++tailSize; + e = e->Dprev; + if( Marked( e->Lface )) break; + AddToTrail( e->Lface, trail ); + } + eTail = e; + + for( e = eOrig; ! Marked( e->Rface ); ++headSize, e = e->Dnext ) { + AddToTrail( e->Rface, trail ); + ++headSize; + e = e->Oprev; + if( Marked( e->Rface )) break; + AddToTrail( e->Rface, 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; +} + + +static void RenderTriangle( GLUtesselator *tess, 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 ); + AddToTrail( e->Lface, tess->lonelyTriList ); +} + + +static void RenderLonelyTriangles( GLUtesselator *tess, GLUface *f ) +{ + /* Now we render all the separate triangles which could not be + * grouped into a triangle fan or strip. + */ + GLUhalfEdge *e; + int newState; + int edgeState = -1; /* force edge state output for first vertex */ + + CALL_BEGIN_OR_BEGIN_DATA( 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->Rface->inside; + if( edgeState != newState ) { + edgeState = newState; + CALL_EDGE_FLAG_OR_EDGE_FLAG_DATA( edgeState ); + } + } + CALL_VERTEX_OR_VERTEX_DATA( e->Org->data ); + + e = e->Lnext; + } while( e != f->anEdge ); + } + CALL_END_OR_END_DATA(); +} + + +static void RenderFan( GLUtesselator *tess, 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). + */ + CALL_BEGIN_OR_BEGIN_DATA( GL_TRIANGLE_FAN ); + CALL_VERTEX_OR_VERTEX_DATA( e->Org->data ); + CALL_VERTEX_OR_VERTEX_DATA( e->Dst->data ); + + while( ! Marked( e->Lface )) { + e->Lface->marked = TRUE; + --size; + e = e->Onext; + CALL_VERTEX_OR_VERTEX_DATA( e->Dst->data ); + } + + assert( size == 0 ); + CALL_END_OR_END_DATA(); +} + + +static void RenderStrip( GLUtesselator *tess, 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). + */ + CALL_BEGIN_OR_BEGIN_DATA( GL_TRIANGLE_STRIP ); + CALL_VERTEX_OR_VERTEX_DATA( e->Org->data ); + CALL_VERTEX_OR_VERTEX_DATA( e->Dst->data ); + + while( ! Marked( e->Lface )) { + e->Lface->marked = TRUE; + --size; + e = e->Dprev; + CALL_VERTEX_OR_VERTEX_DATA( e->Org->data ); + if( Marked( e->Lface )) break; + + e->Lface->marked = TRUE; + --size; + e = e->Onext; + CALL_VERTEX_OR_VERTEX_DATA( e->Dst->data ); + } + + assert( size == 0 ); + CALL_END_OR_END_DATA(); +} + + +/************************ 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). + */ +void __gl_renderBoundary( GLUtesselator *tess, GLUmesh *mesh ) +{ + GLUface *f; + GLUhalfEdge *e; + + for( f = mesh->fHead.next; f != &mesh->fHead; f = f->next ) { + if( f->inside ) { + CALL_BEGIN_OR_BEGIN_DATA( GL_LINE_LOOP ); + e = f->anEdge; + do { + CALL_VERTEX_OR_VERTEX_DATA( e->Org->data ); + e = e->Lnext; + } while( e != f->anEdge ); + CALL_END_OR_END_DATA(); + } + } +} + + +/************************ Quick-and-dirty decomposition ******************/ + +#define SIGN_INCONSISTENT 2 + +static int ComputeNormal( GLUtesselator *tess, GLdouble norm[3], int 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. + */ +{ + CachedVertex *v0 = tess->cache; + CachedVertex *vn = v0 + tess->cacheCount; + CachedVertex *vc; + GLdouble dot, xc, yc, zc, xp, yp, zp, n[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 = v0 + 1; + xc = vc->coords[0] - v0->coords[0]; + yc = vc->coords[1] - v0->coords[1]; + zc = vc->coords[2] - v0->coords[2]; + while( ++vc < vn ) { + xp = xc; yp = yc; zp = zc; + xc = vc->coords[0] - v0->coords[0]; + yc = vc->coords[1] - v0->coords[1]; + zc = vc->coords[2] - v0->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). + */ +GLboolean __gl_renderCache( GLUtesselator *tess ) +{ + CachedVertex *v0 = tess->cache; + CachedVertex *vn = v0 + tess->cacheCount; + CachedVertex *vc; + GLdouble norm[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; + } + + /* Make sure we do the right thing for each winding rule */ + switch( tess->windingRule ) { + case GLU_TESS_WINDING_ODD: + case GLU_TESS_WINDING_NONZERO: + break; + case GLU_TESS_WINDING_POSITIVE: + if( sign < 0 ) return TRUE; + break; + case GLU_TESS_WINDING_NEGATIVE: + if( sign > 0 ) return TRUE; + break; + case GLU_TESS_WINDING_ABS_GEQ_TWO: + return TRUE; + } + + CALL_BEGIN_OR_BEGIN_DATA( tess->boundaryOnly ? GL_LINE_LOOP + : (tess->cacheCount > 3) ? GL_TRIANGLE_FAN + : GL_TRIANGLES ); + + CALL_VERTEX_OR_VERTEX_DATA( v0->data ); + if( sign > 0 ) { + for( vc = v0+1; vc < vn; ++vc ) { + CALL_VERTEX_OR_VERTEX_DATA( vc->data ); + } + } else { + for( vc = vn-1; vc > v0; --vc ) { + CALL_VERTEX_OR_VERTEX_DATA( vc->data ); + } + } + CALL_END_OR_END_DATA(); + return TRUE; +} |