normal.h File Reference

#include "tess.h"

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Functions
void	__gl_projectPolygon (GLUtesselator *tess)

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().

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