gl_PointSize(3) contains size of rasterized points, in pixels


gl_PointSize is a member of the gl_PerVertex named block:

    out gl_PerVertex {
        vec4 gl_Position;
        float gl_PointSize;
        float gl_ClipDistance[];


In the vertex, tessellation evaluation and geometry languages, a single global instance of the gl_PerVertex named block is available and its gl_PointSize member is an output that receives the intended size of the point to be rasterized, in pixels. It may be written at any time during shader execution. If GL_PROGRAM_POINT_SIZE is enabled, gl_PointSize is used to determine the size of rasterized points, otherwise it is ignored by the rasterization stage.

In the tessellation control language, the gl_PerVertex named block is used to construct an array, gl_out[], whose members become available as inputs to the subsequent tessellation evaluation shader.

The value of gl_PointSize (or the gl_PointSize member of the gl_out[] array, in the case of the tessellation control shader) is undefined after the vertex, tessellation control, and tessellation evaluation shading stages if the corresponding shader executable does not write to gl_PointSize. It is also undefined after the geometry processing stage if the geometry shader executable calls EmitVertex() without having written gl_PointSize since the last call to EmitVertex() (or hasn't written it at all).

In the tessellation control, tessellation evaluation and geometry languages, the gl_PerVertex named block is used to construct an array, gl_in[] of per-vertex or per-control point inputs whose content represents the corresponding outputs written by the previous stage.


OpenGL Shading Language Version
Variable Name 1.10 1.20 1.30 1.40 1.50 3.30 4.00 4.10 4.20 4.30 4.40 4.50
gl_PointSize (vertex shader)
gl_PointSize (geometry shader) - - - -
gl_PointSize (tessellation evaluation shader) - - - - - -


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Copyright © 2011-2014 Khronos Group