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Name
SGIX_color_table_index_mode
Name Strings
GL_SGIX_color_table_index_mode
Version
$Date: 1997/04/07 20:05:51 $ $Revision: 1.1 $
Number
XXX
Dependencies
SGI_color_table affects the definition of this extension
Overview
Currently the mapping from a color value to an index is defined mathematically as
clamp your (float) value to [0,1], multiply by the table size-1 and round.
This is less interesting for an s10e5 format pixel where we would like to use
"all" the bits as an index, not just the bits that are good in [0,1].
The answer is to specify that the float color value is converted to the framebuffer
format and then the high order bits are taken as necessary to index the power of
two lookup table. In the silly case where the table is larger than the number of
bits we have, the lsb's of the index are 0 filled.
Issues
the down and dirty nature of this extension may offend the puritanical sensibilities of
certain clean minded types.
New Procedures and Functions
None.
New Tokens
Accepted by the <pname> parameter of ColorTableParameterivSGI,
ColorTableParameterfvSGI, GetColorTableParameterivSGI, and
GetColorTableParameterfvSGI:
COLOR_TABLE_INDEX_MODE 0xXXXX
Accepted by the <params> parameter of ColorTableParameterivSGI,
ColorTableParameterfvSGI
COLOR_TABLE_BITS 0xXXXX
COLOR_TABLE_ARITH 0xXXXX
Additions to Chapter 2 of the 1.0 Specification (OpenGL Operation)
None
Additions to Chapter 3 of the 1.0 Specification (Rasterization)
if the value of COLOR_TABLE_INDEX_MODE is COLOR_TABLE_BITS then
XXX Specify that the index is computed by converting the float color value to
the framebuffer format and taking the required most significan bits as an
index into the color table.
if the value of COLOR_TABLE_INDEX_MODE is COLOR_TABLE_ARITH then
do it like it already says.
Additions to Chapter 4 of the 1.0 Specification (Per-Fragment Operations
and the Framebuffer)
None
Additions to Chapter 5 of the 1.0 Specification (Special Functions)
None
Additions to Chapter 6 of the 1.0 Specification (State and State Requests)
Additions to the GLX Specification
None
GLX Protocol
XXX
Dependencies on SGI_color_table
If SGI_color_table must be supported to support SGI_color_table_index_mode.
Errors
XXX incomplete
New State
Get Value Get Command Type Initial Value Attribute
--------- ----------- ---- ------------- ---------
COLOR_TABLE_INDEX_MODE GetColorTableParameterfvSGI Z2 COLOR_TABLE_ARITH pixel
New Implementation Dependent State