OpenGL.GL.ARB.vertex_program

OpenGL extension ARB.vertex_program

This module customises the behaviour of the OpenGL.raw.GL.ARB.vertex_program to provide a more Python-friendly API

Overview (from the spec)

Unextended OpenGL mandates a certain set of configurable per-vertex computations defining vertex transformation, texture coordinate generation and transformation, and lighting. Several extensions have added further per-vertex computations to OpenGL. For example, extensions have defined new texture coordinate generation modes (ARB_texture_cube_map, NV_texgen_reflection, NV_texgen_emboss), new vertex transformation modes (ARB_vertex_blend, EXT_vertex_weighting), new lighting modes (OpenGL 1.2's separate specular and rescale normal functionality), several modes for fog distance generation (NV_fog_distance), and eye-distance point size attenuation (EXT/ARB_point_parameters).

Each such extension adds a small set of relatively inflexible per-vertex computations.

This inflexibility is in contrast to the typical flexibility provided by the underlying programmable floating point engines (whether micro-coded vertex engines, DSPs, or CPUs) that are traditionally used to implement OpenGL's per-vertex computations. The purpose of this extension is to expose to the OpenGL application writer a significant degree of per-vertex programmability for computing vertex parameters.

For the purposes of discussing this extension, a vertex program is a sequence of floating-point 4-component vector operations that determines how a set of program parameters (defined outside of OpenGL's Begin/End pair) and an input set of per-vertex parameters are transformed to a set of per-vertex result parameters.

The per-vertex computations for standard OpenGL given a particular set of lighting and texture coordinate generation modes (along with any state for extensions defining per-vertex computations) is, in essence, a vertex program. However, the sequence of operations is defined implicitly by the current OpenGL state settings rather than defined explicitly as a sequence of instructions.

This extension provides an explicit mechanism for defining vertex program instruction sequences for application-defined vertex programs. In order to define such vertex programs, this extension defines a vertex programming model including a floating-point 4-component vector instruction set and a relatively large set of floating-point 4-component registers.

The extension's vertex programming model is designed for efficient hardware implementation and to support a wide variety of vertex programs. By design, the entire set of existing vertex programs defined by existing OpenGL per-vertex computation extensions can be implemented using the extension's vertex programming model.

The official definition of this extension is available here: http://www.opengl.org/registry/specs/ARB/vertex_program.txt