Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

glutessproperty(3g) [osx man page]


gluTessProperty - set a tessellation object property C SPECIFICATION
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 inter- preted 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, posi- tive, 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 ver- tex 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, gluNewTess GLUTESSPROPERTY(3G)

Check Out this Related Man Page


gluNextContour - mark the beginning of another contour C SPECIFICATION
void gluNextContour( GLUtesselator* tess, GLenum type ) PARAMETERS
tess Specifies the tessellation object (created with gluNewTess). type Specifies the type of the contour being defined. Valid values are GLU_EXTERIOR, GLU_INTERIOR, GLU_UNKNOWN, GLU_CCW, and GLU_CW. DESCRIPTION
gluNextContour is used in describing polygons with multiple contours. After the first contour has been described through a series of gluTessVertex calls, a gluNextContour call indicates that the previous contour is complete and that the next contour is about to begin. Another series of gluTessVertex calls is then used to describe the new contour. This process can be repeated until all contours have been described. type defines what type of contour follows. The legal contour types are as follows: GLU_EXTERIOR An exterior contour defines an exterior boundary of the polygon. GLU_INTERIOR An interior contour defines an interior boundary of the polygon (such as a hole). GLU_UNKNOWN An unknown contour is analyzed by the library to determine if it is interior or exterior. GLU_CCW, GLU_CW The first GLU_CCW or GLU_CW contour defined is considered to be exterior. All other contours are considered to be exte- rior if they are oriented in the same direction (clockwise or counterclockwise) as the first contour, and interior if they are not. If one contour is of type GLU_CCW or GLU_CW, then all contours must be of the same type (if they are not, then all GLU_CCW and GLU_CW con- tours will be changed to GLU_UNKNOWN). Note that there is no real difference between the GLU_CCW and GLU_CW contour types. Before the first contour is described, gluNextContour can be called to define the type of the first contour. If gluNextContour is not called before the first contour, then the first contour is marked GLU_EXTERIOR. This command is obsolete and is provided for backward compatibility only. Calls to gluNextContour are mapped to gluTessEndContour followed by gluTessBeginContour. EXAMPLE
A quadrilateral with a triangular hole in it can be described as follows: gluBeginPolygon(tobj); gluTessVertex(tobj, v1, v1); gluTessVertex(tobj, v2, v2); gluTessVertex(tobj, v3, v3); gluTessVertex(tobj, v4, v4); gluNextContour(tobj, GLU_INTERIOR); gluTessVertex(tobj, v5, v5); gluTessVertex(tobj, v6, v6); gluTessVertex(tobj, v7, v7); gluEndPolygon(tobj); SEE ALSO
gluBeginPolygon(3G), gluNewTess(3G), gluTessCallback(3G), gluTessVertex(3G), gluTessBeginContour(3G) GLUNEXTCONTOUR(3G)
Man Page