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| /*
** 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: //depot/main/gfx/lib/glu/libtess/render.c#5 $
*/
#include <assert.h>
#include <stddef.h>
#include <gluos.h>
#include "mesh.h"
#include "render.h"
#include "tess.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) do { \
while( (t) != NULL ) { \
(t)->marked = FALSE; t = (t)->trail; \
} \
} while(0) /* 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;
} |
Portage GLUtessellator pour récupérer les triangles, triangleFan et triangleStrip
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