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/*
* SGI FREE SOFTWARE LICENSE B (Version 2.0, Sept. 18, 2008)
* Copyright (C) 1991-2000 Silicon Graphics, Inc. All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice including the dates of first publication and
* either this permission notice or a reference to
* http://oss.sgi.com/projects/FreeB/
* shall be included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* SILICON GRAPHICS, INC. BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF
* OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*
* Except as contained in this notice, the name of Silicon Graphics, Inc.
* shall not be used in advertising or otherwise to promote the sale, use or
* other dealings in this Software without prior written authorization from
* Silicon Graphics, Inc.
*/
/*
** Author: Eric Veach, July 1994.
**
*/
#include "gluos.h"
#include "mesh.h"
#include "tess.h"
#include "normal.h"
#include <math.h>
#include <assert.h>
#define TRUE 1
#define FALSE 0
#define Dot(u,v) (u[0]*v[0] + u[1]*v[1] + u[2]*v[2])
#if 0
static void Normalize( GLdouble v[3] )
{
GLdouble len = v[0]*v[0] + v[1]*v[1] + v[2]*v[2];
assert( len > 0 );
len = sqrt( len );
v[0] /= len;
v[1] /= len;
v[2] /= len;
}
#endif
#undef ABS
#define ABS(x) ((x) < 0 ? -(x) : (x))
static int LongAxis( GLdouble v[3] )
{
int i = 0;
if( ABS(v[1]) > ABS(v[0]) ) { i = 1; }
if( ABS(v[2]) > ABS(v[i]) ) { i = 2; }
return i;
}
static void ComputeNormal( GLUtesselator *tess, GLdouble norm[3] )
{
GLUvertex *v, *v1, *v2;
GLdouble c, tLen2, maxLen2;
GLdouble maxVal[3], minVal[3], d1[3], d2[3], tNorm[3];
GLUvertex *maxVert[3], *minVert[3];
GLUvertex *vHead = &tess->mesh->vHead;
int i;
maxVal[0] = maxVal[1] = maxVal[2] = -2 * GLU_TESS_MAX_COORD;
minVal[0] = minVal[1] = minVal[2] = 2 * GLU_TESS_MAX_COORD;
for( v = vHead->next; v != vHead; v = v->next ) {
for( i = 0; i < 3; ++i ) {
c = v->coords[i];
if( c < minVal[i] ) { minVal[i] = c; minVert[i] = v; }
if( c > maxVal[i] ) { maxVal[i] = c; maxVert[i] = v; }
}
}
/* Find two vertices separated by at least 1/sqrt(3) of the maximum
* distance between any two vertices
*/
i = 0;
if( maxVal[1] - minVal[1] > maxVal[0] - minVal[0] ) { i = 1; }
if( maxVal[2] - minVal[2] > maxVal[i] - minVal[i] ) { i = 2; }
if( minVal[i] >= maxVal[i] ) {
/* All vertices are the same -- normal doesn't matter */
norm[0] = 0; norm[1] = 0; norm[2] = 1;
return;
}
/* Look for a third vertex which forms the triangle with maximum area
* (Length of normal == twice the triangle area)
*/
maxLen2 = 0;
v1 = minVert[i];
v2 = maxVert[i];
d1[0] = v1->coords[0] - v2->coords[0];
d1[1] = v1->coords[1] - v2->coords[1];
d1[2] = v1->coords[2] - v2->coords[2];
for( v = vHead->next; v != vHead; v = v->next ) {
d2[0] = v->coords[0] - v2->coords[0];
d2[1] = v->coords[1] - v2->coords[1];
d2[2] = v->coords[2] - v2->coords[2];
tNorm[0] = d1[1]*d2[2] - d1[2]*d2[1];
tNorm[1] = d1[2]*d2[0] - d1[0]*d2[2];
tNorm[2] = d1[0]*d2[1] - d1[1]*d2[0];
tLen2 = tNorm[0]*tNorm[0] + tNorm[1]*tNorm[1] + tNorm[2]*tNorm[2];
if( tLen2 > maxLen2 ) {
maxLen2 = tLen2;
norm[0] = tNorm[0];
norm[1] = tNorm[1];
norm[2] = tNorm[2];
}
}
if( maxLen2 <= 0 ) {
/* All points lie on a single line -- any decent normal will do */
norm[0] = norm[1] = norm[2] = 0;
norm[LongAxis(d1)] = 1;
}
}
static void CheckOrientation( GLUtesselator *tess )
{
GLdouble area;
GLUface *f, *fHead = &tess->mesh->fHead;
GLUvertex *v, *vHead = &tess->mesh->vHead;
GLUhalfEdge *e;
/* When we compute the normal automatically, we choose the orientation
* so that the the sum of the signed areas of all contours is non-negative.
*/
area = 0;
for( f = fHead->next; f != fHead; f = f->next ) {
e = f->anEdge;
if( e->winding <= 0 ) continue;
do {
area += (e->Org->s - e->Dst->s) * (e->Org->t + e->Dst->t);
e = e->Lnext;
} while( e != f->anEdge );
}
if( area < 0 ) {
/* Reverse the orientation by flipping all the t-coordinates */
for( v = vHead->next; v != vHead; v = v->next ) {
v->t = - v->t;
}
tess->tUnit[0] = - tess->tUnit[0];
tess->tUnit[1] = - tess->tUnit[1];
tess->tUnit[2] = - tess->tUnit[2];
}
}
#ifdef FOR_TRITE_TEST_PROGRAM
#include <stdlib.h>
extern int RandomSweep;
#define S_UNIT_X (RandomSweep ? (2*drand48()-1) : 1.0)
#define S_UNIT_Y (RandomSweep ? (2*drand48()-1) : 0.0)
#else
#if defined(SLANTED_SWEEP)
/* The "feature merging" is not intended to be complete. There are
* special cases where edges are nearly parallel to the sweep line
* which are not implemented. The algorithm should still behave
* robustly (ie. produce a reasonable tesselation) in the presence
* of such edges, however it may miss features which could have been
* merged. We could minimize this effect by choosing the sweep line
* direction to be something unusual (ie. not parallel to one of the
* coordinate axes).
*/
#define S_UNIT_X 0.50941539564955385 /* Pre-normalized */
#define S_UNIT_Y 0.86052074622010633
#else
#define S_UNIT_X 1.0
#define S_UNIT_Y 0.0
#endif
#endif
/* Determine the polygon normal and project vertices onto the plane
* of the polygon.
*/
void __gl_projectPolygon( GLUtesselator *tess )
{
GLUvertex *v, *vHead = &tess->mesh->vHead;
GLdouble norm[3];
GLdouble *sUnit, *tUnit;
int i, computedNormal = FALSE;
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 );
computedNormal = TRUE;
}
sUnit = tess->sUnit;
tUnit = tess->tUnit;
i = LongAxis( norm );
#if defined(FOR_TRITE_TEST_PROGRAM) || defined(TRUE_PROJECT)
/* Choose the initial sUnit vector to be approximately perpendicular
* to the normal.
*/
Normalize( norm );
sUnit[i] = 0;
sUnit[(i+1)%3] = S_UNIT_X;
sUnit[(i+2)%3] = S_UNIT_Y;
/* Now make it exactly perpendicular */
w = Dot( sUnit, norm );
sUnit[0] -= w * norm[0];
sUnit[1] -= w * norm[1];
sUnit[2] -= w * norm[2];
Normalize( sUnit );
/* Choose tUnit so that (sUnit,tUnit,norm) form a right-handed frame */
tUnit[0] = norm[1]*sUnit[2] - norm[2]*sUnit[1];
tUnit[1] = norm[2]*sUnit[0] - norm[0]*sUnit[2];
tUnit[2] = norm[0]*sUnit[1] - norm[1]*sUnit[0];
Normalize( tUnit );
#else
/* Project perpendicular to a coordinate axis -- better numerically */
sUnit[i] = 0;
sUnit[(i+1)%3] = S_UNIT_X;
sUnit[(i+2)%3] = S_UNIT_Y;
tUnit[i] = 0;
tUnit[(i+1)%3] = (norm[i] > 0) ? -S_UNIT_Y : S_UNIT_Y;
tUnit[(i+2)%3] = (norm[i] > 0) ? S_UNIT_X : -S_UNIT_X;
#endif
/* Project the vertices onto the sweep plane */
for( v = vHead->next; v != vHead; v = v->next ) {
v->s = Dot( v->coords, sUnit );
v->t = Dot( v->coords, tUnit );
}
if( computedNormal ) {
CheckOrientation( tess );
}
}
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