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WGL_EXT_depth_float


Name


    EXT_depth_float

Name Strings


    WGL_EXT_depth_float

Version


    Date: 1/27/1999  Version 1.4

Number


    177

Dependencies


    WGL_EXT_extensions_string is required.
WGL_EXT_pixel_format is required.

Overview


    For perspective scenes, the density of objects (vertices) increases
as the distance from the eye increases. For a linear depth buffer,
this means that objects (vertices) are sparse for a large portion of
the depth range and are dense for a small portion of the depth buffer.

This behavior is obvious if you consider standing in a boat looking
at the shore. The near objects include only the boat while the far
objects include the entire shoreline which may include an entire city.

A non-linear (floating-point) depth buffer helps this problem. If
the near clipping plane is set to 1.0, and the far clipping plane is
set to 0.0, a much greater resolution of objects can occur.

New Procedures and Functions


    None

New Tokens


    Accepted by the <attribute> parameter of wglGetPixelFormatAttribivEXT,
wglGetPixelFormatAttribfvEXT, and wglChoosePixelFormatExEXT:

WGL_DEPTH_FLOAT_EXT 0x2040

Additions to Chapter 2 of the 1.2 Specification (OpenGL Operation)


    Each of n and f are clamped to lie within [0,1], as are all arguments
of type clampd or clampf. zw is taken to be represented in either
fixed-point or floating-point depending on the attributes of the
window.

If the depth buffer is a fixed-point format, then zw is taken to be
represented in fixed-point with at least as many bits as there are
in the depth buffer of the framebuffer. We assume that the fixed-point
representation used represents each value k/(2^m - 1), where k is in
the set {0,1,...,2^m - 1}, as k (e.g. 1.0 is represented in the binary
as a string of all ones).

If the depth buffer is a floating-point format, then zw is taken to be
represented in floating-point with at least as many bits as there are
in the depth buffer of the framebuffer. The floating-point
representation is implementation dependent.

Additions to Chapter 3 of the 1.2 Specification (Rasterization)


    None

Additions to Chapter 4 of the 1.2 Specification (Per-Fragment Operations and the Framebuffer)


    None

Additions to Chapter 5 of the 1.2 Specification (Special Functions)


    None

Additions to Chapter 6 of the 1.2 Specification (State and State Requests)


    None

Additions to the WGL Specification


    None

Errors


    None

New State


    None

New Implementation Dependent State


    None

Implementation Support


   List of OpenGL implementations supporting the WGL_EXT_depth_float extension

Original File


   Original text file for the WGL_EXT_depth_float extension


Page generated on Sun Nov 20 18:37:48 2005