GLPOINTS

GLPOINTS refers to the OpenGL primitive mode GL_POINTS, used to render one point per vertex. In this mode, each vertex in the supplied vertex array or buffer generates a single point at the position defined by the vertex, producing a collection of discrete points on the screen. Points are useful for particle systems, point clouds, star fields, and lightweight markers.

In legacy and fixed-function pipelines, the size of points can be set globally with glPointSize. In modern programmable pipelines, per-vertex point size can be specified by writing to gl_PointSize in the vertex shader, provided the GL_PROGRAM_POINT_SIZE capability is enabled. When enabled, the size value emitted per vertex determines the corresponding point size; otherwise a fixed size is used as configured by glPointSize. Point sizes are bounded by hardware limits (GL_POINT_SIZE_RANGE and GL_MAX_POINT_SIZE).

Points are rasterized in window coordinates, with their appearance potentially affected by the fragment shader. In the fragment stage, the built-in variable gl_PointCoord gives the coordinates within the point, enabling texture sampling to render textured or circular points. A common technique is to sample a texture or to discard fragments outside a circular mask to achieve round points.

Draw calls using GL_POINTS typically employ glDrawArrays or glDrawElements with the mode set to GL_POINTS, using either legacy arrays or modern vertex buffer objects and shaders. Performance and visual quality depend on point size, the number of points, and whether per-point attributes (such as size or color) are used.

GLPOINTS remains a foundational primitive in OpenGL, offering a straightforward mechanism to render many small primitives efficiently, while requiring shader logic for advanced sizing and textured appearances.