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 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