Index for Section 3

Alphabetical listing for G

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gluTessProperty()
NAME
  gluTessProperty - set a tessellation object property

SYNOPSIS
  void gluTessProperty(
	  GLUtesselator* tess,
	  GLenum which,
	  GLdouble data );

PARAMETERS
  tess
      Specifies the tessellation object (created with gluNewTess()).

  which
      Specifies the property to be set. Valid values are
      GLU_TESS_WINDING_RULE, GLU_TESS_BOUNDARY_ONLY, GLU_TESS_TOLERANCE.

  data
      Specifies the value of the indicated property.

DESCRIPTION
  gluTessProperty() is used to control properties stored in a tessellation
  object. These properties affect the way that the polygons are interpreted
  and rendered. The legal values for which are as follows:

  GLU_TESS_WINDING_RULE
      Determines which parts of the polygon are on the "interior".  data may
      be set to one of GLU_TESS_WINDING_ODD, GLU_TESS_WINDING_NONZERO,
      GLU_TESS_WINDING_POSITIVE, or GLU_TESS_WINDING_NEGATIVE, or
      GLU_TESS_WINDING_ABS_GEQ_TWO.

      To understand how the winding rule works, consider that the input
      contours partition the plane into regions. The winding rule determines
      which of these regions are inside the polygon.

      For a single contour C, the winding number of a point x is simply the
      signed number of revolutions we make around x as we travel once around
      C (where CCW is positive). When there are several contours, the
      individual winding numbers are summed. This procedure associates a
      signed integer value with each point x in the plane. Note that the
      winding number is the same for all points in a single region.

      The winding rule classifies a region as "inside" if its winding number
      belongs to the chosen category (odd, nonzero, positive, negative, or
      absolute value of at least two). The previous GLU tessellator (prior to
      GLU 1.2) used the "odd" rule. The "nonzero" rule is another common way
      to define the interior.  The other three rules are useful for polygon
      CSG operations.

  GLU_TESS_BOUNDARY_ONLY
      Is a boolean value ("value" should be set to GL_TRUE or GL_FALSE). When
      set to GL_TRUE, a set of closed contours separating the polygon
      interior and exterior are returned instead of a tessellation. Exterior
      contours are oriented CCW with respect to the normal; interior contours
      are oriented CW. The GLU_TESS_BEGIN and GLU_TESS_BEGIN_DATA callbacks
      use the type GL_LINE_LOOP for each contour.

  GLU_TESS_TOLERANCE
      Specifies a tolerance for merging features to reduce the size of the
      output. For example, two vertices that are very close to each other
      might be replaced by a single vertex. The tolerance is multiplied by
      the largest coordinate magnitude of any input vertex; this specifies
      the maximum distance that any feature can move as the result of a
      single merge operation. If a single feature takes part in several merge
      operations, the total distance moved could be larger.

      Feature merging is completely optional; the tolerance is only a hint.
      The implementation is free to merge in some cases and not in others, or
      to never merge features at all. The initial tolerance is 0.

      The current implementation merges vertices only if they are exactly
      coincident, regardless of the current tolerance. A vertex is spliced
      into an edge only if the implementation is unable to distinguish which
      side of the edge the vertex lies on. Two edges are merged only when
      both endpoints are identical.

SEE ALSO
  gluGetTessProperty(3)

Index for Section 3

Alphabetical listing for G

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