P

parameter

A value passed as an argument to an OpenGL command. Sometimes one of the values passed by reference to an OpenGL command.

perspective division

The division of x, y, and z by w, carried out in clip coordinates. See also clip coordinates.

pixel

Picture element. The bits at location (x, y) of all the bitplanes in the frame buffer constitute the single pixel (x, y). In an image in client memory, a pixel is one group of elements. In OpenGL window coordinates, each pixel corresponds to a 1.0x1.0 screen area. The coordinates of the lower left corner of the pixel names x, y are (x, y), and the upper right corner are (x+1, y+1).

point

An exact location in space, which is rendered as a finite-diameter dot.

polygon

A near-planar surface bounded by edges specified by vertices. Each triangle of a triangle mesh is a polygon, as is each quadrilateral of a quadrilateral mesh. The rectangle specified by glRect is also a polygon.

primitive

A shape (such as a point, line, polygon, bitmap or image) that can be drawn, stored, and manipulated as a discrete entity; elements from which large graphic designs are created.

projection matrix

The 4x4 matrix that transforms points, lines, polygons, and raster positions from eye coordinates to clip coordinates.