normal.c File Reference

#include "gluos.h"
#include "mesh.h"
#include "tess.h"
#include "normal.h"
#include <math.h>
#include <assert.h>

Include dependency graph for normal.c:

Go to the source code of this file.

Macros
#define	TRUE   1
#define	FALSE   0
#define	Dot(u, v)   (u[0]*v[0] + u[1]*v[1] + u[2]*v[2])
#define	ABS(x)   ((x) < 0 ? -(x) : (x))
#define	S_UNIT_X   1.0
#define	S_UNIT_Y   0.0

Functions
static int	LongAxis (GLdouble v[3])
static void	ComputeNormal (GLUtesselator *tess, GLdouble norm[3])
static void	CheckOrientation (GLUtesselator *tess)
void	__gl_projectPolygon (GLUtesselator *tess)

Macro Definition Documentation

ABS

#define ABS

(

x

)

((x) < 0 ? -(x) : (x))

Dot

#define Dot	(		u,
			v
	)		(u[0]*v[0] + u[1]*v[1] + u[2]*v[2])

FALSE

#define FALSE   0

S_UNIT_X

#define S_UNIT_X   1.0

S_UNIT_Y

#define S_UNIT_Y   0.0

TRUE

#define TRUE   1

Function Documentation

__gl_projectPolygon()

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 );
  }
}

References CheckOrientation(), ComputeNormal(), GLUvertex::coords, Dot, FALSE, LongAxis(), GLUtesselator::mesh, GLUvertex::next, GLUtesselator::normal, GLUvertex::s, S_UNIT_X, S_UNIT_Y, GLUtesselator::sUnit, GLUvertex::t, TRUE, GLUtesselator::tUnit, and GLUmesh::vHead.

Referenced by gluTessEndPolygon().

Here is the call graph for this function:

Here is the caller graph for this function:

CheckOrientation()

static void CheckOrientation ( GLUtesselator *  tess )

static

{
  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 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];
  }
}

References GLUface::anEdge, GLUmesh::fHead, GLUhalfEdge::Lnext, GLUtesselator::mesh, GLUvertex::next, GLUface::next, GLUhalfEdge::Org, GLUvertex::s, GLUvertex::t, GLUtesselator::tUnit, GLUmesh::vHead, and GLUhalfEdge::winding.

Referenced by __gl_projectPolygon().

Here is the caller graph for this function:

ComputeNormal()

static void ComputeNormal ( GLUtesselator *  tess, GLdouble  norm[3]  )

static

{
  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;
  }
}

References GLUvertex::coords, GLU_TESS_MAX_COORD, LongAxis(), GLUtesselator::mesh, GLUvertex::next, and GLUmesh::vHead.

Referenced by __gl_projectPolygon().

Here is the call graph for this function:

Here is the caller graph for this function:

LongAxis()

static int LongAxis ( GLdouble  v[3] )

static

{
  int i = 0;
 
  if( ABS(v[1]) > ABS(v[0]) ) { i = 1; }
  if( ABS(v[2]) > ABS(v[i]) ) { i = 2; }
  return i;
}

References ABS.

Referenced by __gl_projectPolygon(), and ComputeNormal().

Here is the caller graph for this function: