OpenGL.GL.APPLE.float_pixels

OpenGL extension APPLE.float_pixels

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

Overview (from the spec)

This extensions adds texture types, texture internal formats and color buffers composed of both 32 bit and 16 floating point numbers. 16 bit floats (half float) are very similar to the IEEE single-precision floating-point standard, except that it has only 5 exponent bits and 10 mantissa bits. All floating point numbers are clamped to the limits of the range representable by their respective format.

Specifically, APPLE_float_pixels adds four pieces of functionality to OpenGL. First, it provides an HALF_APPLE texture type allowing clients to pass textures in the half float format. Second, it adds 12 additional sized internal formats to allow OpenGL to process and maintain texture data in the requested format if possible. Next, it provides the COLOR_FLOAT_APPLE pixel format to allow creation of floating point and half float color buffers. Lastly, it provides an additional query to allow clients to verify that they have a floating point color buffer.

The HALF_APPLE texture type allows clients to use source textures composed of half float color components. This constant is use in the type parameter in DrawPixels, ReadPixels and texturing commands with a corresponding GL half data type, which corresponds to a 16 bit half float, and has no special interpretation.

Clients can use the 12 additional (6 floating point and 6 half float) sized internal texture formats to specify the mapping of R, G, B and A values to texture components, as they would with any other sized internal texture format. Note, as is the standard practice with OpenGL, implementations should map the sized internal texture R, G, B and A values to internal components with memory allocations as close as possible to those specified in the sized internal format.

Floating point color buffers are created by specifying the appropriate color floating point pixel format attribute for the windowing system API in use by the client. Both 128 bit and 64 bit floating point color buffers can be supported, the former with full 32 bit floating point components and the latter with 16 bit half float components.

Additionally, clients can query to see if they have a floating point color buffer using GetBooleanv with COLOR_FLOAT_APPLE as the get value. The number of bits per color buffer component can be determined in the usual manner.

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