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GLPOINTSIZE() GLPOINTSIZE() NAME glPointSize - specify the diameter of rasterized points C SPECIFICATION void glPointSize( GLfloat size ) delim $$ PARAMETERS size Specifies the diameter of rasterized points. The initial value is 1. DESCRIPTION glPointSize specifies the rasterized diameter of both aliased and an- tialiased points. Using a point size other than 1 has different ef- fects, depending on whether point antialiasing is enabled. To enable and disable point antialiasing, call glEnable and glDisable with argu- ment GL_POINT_SMOOTH. Point antialiasing is initially disabled. If point antialiasing is disabled, the actual size is determined by rounding the supplied size to the nearest integer. (If the rounding results in the value 0, it is as if the point size were 1.) If the rounded size is odd, then the center point ($ x $, $ y $) of the pixel fragment that represents the point is computed as ( $ |_ ~ x sub w ~ _| ~+~ .5 $, $ |_ ~ y sub w ~ _| ~+~ .5 $) where $w$ subscripts indicate window coordinates. All pixels that lie within the square grid of the rounded size centered at ($ x $, $ y $) make up the fragment. If the size is even, the center point is ( $ |_ ~ x sub w ~+~ .5 ~ _|$, $ |_ ~ y sub w ~+~ .5 ~ _| $) and the rasterized fragment's centers are the half-integer window coor- dinates within the square of the rounded size centered at ($ x $, $ y $). All pixel fragments produced in rasterizing a nonantialiased point are assigned the same associated data, that of the vertex corresponding to the point. If antialiasing is enabled, then point rasterization produces a frag- ment for each pixel square that intersects the region lying within the circle having diameter equal to the current point size and centered at the point's ($ x sub w $, $ y sub w $). The coverage value for each fragment is the window coordinate area of the intersection of the cir- cular region with the corresponding pixel square. This value is saved and used in the final rasterization step. The data associated with each fragment is the data associated with the point being rasterized. Not all sizes are supported when point antialiasing is enabled. If an unsupported size is requested, the nearest supported size is used. Only size 1 is guaranteed to be supported; others depend on the imple- mentation. To query the range of supported sizes and the size differ- ence between supported sizes within the range, call glGet with argu- ments GL_POINT_SIZE_RANGE and GL_POINT_SIZE_GRANULARITY. NOTES The point size specified by glPointSize is always returned when GL_POINT_SIZE is queried. Clamping and rounding for aliased and an- tialiased points have no effect on the specified value. A non-antialiased point size may be clamped to an implementation-depen- dent maximum. Although this maximum cannot be queried, it must be no less than the maximum value for antialiased points, rounded to the nearest integer value. ERRORS GL_INVALID_VALUE is generated if size is less than or equal to 0. GL_INVALID_OPERATION is generated if glPointSize is executed between the execution of glBegin and the corresponding execution of glEnd. ASSOCIATED GETS glGet with argument GL_POINT_SIZE glGet with argument GL_POINT_SIZE_RANGE glGet with argument GL_POINT_SIZE_GRANULARITY glIsEnabled with argument GL_POINT_SMOOTH SEE ALSO glEnable GLPOINTSIZE()
NAME | C SPECIFICATION | PARAMETERS | DESCRIPTION | NOTES | ERRORS | ASSOCIATED GETS | SEE ALSO
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