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OpenGL 1.1 for AIX: Reference Manual

glPointSize Subroutine


Specifies the diameter of rasterized points.


OpenGL C bindings library: libGL.a

C Syntax

void glPointSize(GLfloat Size)


Size Specifies the diameter of rasterized points. The default is 1.0.


The glPointSize subroutine specifies the rasterized diameter of both aliased and antialiased points. Using a point size other than 1.0 has different effects, depending on whether point antialiasing is enabled. Point antialiasing is controlled by calling the glEnable and glDisable subroutines with argument GL_POINT_SMOOTH.

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 (zero), it is as if the point size were 1 (one).) If the rounded size is odd, the center point (xy) of the pixel fragment that represents the point is computed as

(floor(xw) + 0.5, floor(yw) + 0.5)

where w subscripts indicate window coordinates. All pixels that lie within the square grid of the rounded size centered at (xy) make up the fragment. If the size is even, the center point is

(floor(xw + 0.5), floor(yw + 0.5))

and the rasterized fragment's centers are the half-integer window coordinates within the square of the rounded size centered at (xy). 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, point rasterization produces a fragment 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 (xw, yw). The coverage value for each fragment is the window coordinate area of the intersection of the circular 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 1.0 is guaranteed to be supported; others are dependent on the implementation. The range of supported sizes and the size difference between supported sizes within the range can be queried by calling the glGet subroutine with the GL_POINT_SIZE_RANGE and GL_POINT_SIZE_GRANULARITY arguments.


The point size specified by glPointSize is always returned when GL_POINT_SIZE is queried. Clamping and rounding for aliased and antialiased points have no effect on the specified value.

Nonantialiased point size may be clamped to a maximum that depends on the implementation. Although this maximum cannot be queried, it must be no less than the maximum value for antialiased points, rounded to the nearest integer value.


GL_INVALID_VALUE Size is less than or equal to 0.
GL_INVALID_OPERATION The glPointSize subroutine is called between a call to glBegin and the corresponding call to glEnd.

Associated Gets

Associated gets for the glPointSize subroutine are as follows. (See the glGet subroutine for more information.)

glGet with argument GL_POINT_SIZE

glGet with argument GL_POINT_SIZE_RANGE


glIsEnabled with argument GL_POINT_SMOOTH.


/usr/include/GL/gl.h Contains C language constants, variable type definitions, and ANSI function prototypes for OpenGL.

Related Information

The glBegin or glEnd subroutine, glEnable or Disable subroutine.

OpenGL Overview.

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