| GL_EXT_shared_texture_palette |
EXT_shared_texture_palette
GL_EXT_shared_texture_palette
Jon Leech, SGI (ljp 'at' sgi.com)
Mark J. Kilgard, NVIDIA Corporation (mjk 'at' nvidia.com)
Last Modified Date: March 24, 2004
Revision: 1.4
141
Mesa.
Selected NVIDIA GPUs: NV1x (GeForce 256, GeForce2, GeForce4 MX,
GeForce4 Go, Quadro, Quadro2), NV2x (GeForce3, GeForce4 Ti,
Quadro DCC, Quadro4 XGL), and NV3x (GeForce FX 5xxxx, Quadro FX
1000/2000/3000). NV3 (Riva 128) and NV4 (TNT, TNT2) GPUs and NV4x
GPUs do NOT support this functionality (no hardware support).
Future NVIDIA GPU designs will no longer support paletted textures.
S3 ProSavage, Savage 2000.
3Dfx Voodoo3, Voodoo5.
3Dlabs GLINT.
EXT_paletted_texture is required.
EXT_shared_texture_palette defines a shared texture palette which may be
used in place of the texture object palettes provided by
EXT_paletted_texture. This is useful for rapidly changing a palette
common to many textures, rather than having to reload the new palette
for each texture. The extension acts as a switch, causing all lookups
that would normally be done on the texture's palette to instead use the
shared palette.
None.
* Do we want to use a new <target> to ColorTable to specify the
shared palette, or can we just infer the new target from the
corresponding Enable?
* A future extension of larger scope might define a "texture palette
object" and bind these objects to texture objects dynamically, rather
than making palettes part of the texture object state as the current
EXT_paletted_texture spec does.
* Should there be separate shared palettes for 1D, 2D, and 3D
textures?
Probably not; palette lookups have nothing to do with the
dimensionality of the texture. If multiple shared palettes
are needed, we should define palette objects.
* There's no proxy mechanism for checking if a shared palette can
be defined with the requested parameters. Will it suffice to
assume that if a texture palette can be defined, so can a shared
palette with the same parameters?
* The changes to the spec are based on changes already made for
EXT_paletted_texture, which means that all three documents must
be referred to. This is quite difficult to read.
* The changes to section 3.8.6, defining how shared palettes are
enabled and disabled, might be better placed in section 3.8.1.
However, the underlying EXT_paletted_texture does not appear to
modify these sections to define exactly how palette lookups are
done, and it's not clear where to put the changes.
* How does the shared texture palette interact with multitexture
support? There is a single global shared texture palette that
all texture units utilize (as opposed to a shared texture palette
per texture unit).
   New Procedures and Functions |
None
Accepted by the <pname> parameters of GetBooleanv, GetIntegerv,
GetFloatv, GetDoublev, IsEnabled, Enable, Disable, ColorTableEXT,
ColorSubTableEXT, GetColorTableEXT, GetColorTableParameterivEXT, and
GetColorTableParameterfd EXT:
SHARED_TEXTURE_PALETTE_EXT 0x81FB
| Additions to Chapter 2 of the 1.1 Specification (OpenGL Operation) |
None
| Additions to Chapter 3 of the 1.1 Specification (Rasterization) |
Section 3.8, 'Texturing,' subsection 'Texture Image Specification' is
modified as follows:
In the Palette Specification Commands section, the sentence
beginning 'target specifies which texture is to' should be changed
to:
target specifies the texture palette or shared palette to be
changed, and may be one of TEXTURE_1D, TEXTURE_2D,
PROXY_TEXTURE_1D, PROXY_TEXTURE_2D, TEXTURE_3D_EXT,
PROXY_TEXTURE_3D_EXT, or SHARED_TEXTURE_PALETTE_EXT.
In the 'Texture State and Proxy State' section, the sentence
beginning 'A texture's palette is initially...' should be changed
to:
There is also a shared palette not associated with any texture,
which may override a texture palette. (Even when multiple texture
units are available, there is still only a single shared texture
palette.) All palettes are initially...
Section 3.8.6, 'Texture Application' is modified by appending the
following:
Use of the shared texture palette is enabled or disabled using the
generic Enable or Disable commands, respectively, with the symbolic
constant SHARED_TEXTURE_PALETTE_EXT.
The required state is one bit indicating whether the shared palette is
enabled or disabled. In the initial state, the shared palettes is
disabled.
| Additions to Chapter 4 of the 1.1 Specification (Per-Fragment Operations and the Frame buffer) |
| Additions to Chapter 5 of the 1.1 Specification (Special Functions) |
| Additions to Chapter 6 of the 1.1 Specification (State and State Requests) |
In the section on GetTexImage, the sentence beginning 'If format is
not COLOR_INDEX...' should be changed to:
If format is not COLOR_INDEX, the texture's indices are passed
through the texture's palette, or the shared palette if one is
enabled, and the resulting components are assigned among R, G, B,
and A according to Table 6.1.
In the GetColorTable section, the first sentence of the second
paragraph should be changed to read:
GetColorTableEXT retrieves the texture palette or shared palette
given by target.
The first sentence of the third paragraph should be changed to read:
Palette parameters can be retrieved using
void GetColorTableParameterivEXT(enum target, enum pname, int *params);
void GetColorTableParameterfvEXT(enum target, enum pname, float *params);
target specifies the texture palette or shared palette being
queried and pname controls which parameter value is returned.
| Additions to the GLX Specification |
None
Get Value Type Get Command Initial Value Description Sec Attribute
-------------------------- ---- --------------------------- ------------- -------------- ----- --------------
SHARED_TEXTURE_PALETTE_EXT B IsEnabled False shared texture 3.8.6 texture/enable
palette enable
SHARED_TEXTURE_PALETTE_EXT I GetColorTableEXT empty shared texture 3.8 -
palette table
COLOR_TABLE_FORMAT_EXT Zn GetColorTableParameterivEXT RGBA shared texture 3.8 -
palette format
COLOR_TABLE_WIDTH_EXT Z+ GetColorTableParameteriv 0 shared texture 3.8 -
palette width
COLOR_TABLE_x_SIZE_EXT 6xZ+ GetColorTableParameteriv 0 shared texture 3.8 -
palette
component sizes
| New Implementation Dependent State |
None
September 4, 2002 - Add missing IP Status / Contact fields
(without bumping the revision) and incorporated Mark's changes
into the registry. (Jon Leech)
July 10, 2002 (version 1.3) - Added "New State" tables entries.
Clarify that there is a single global shared texture palette,
rather than a per-texture unit palette when multitexture is
available. (Mark Kilgard)
March 24, 2004 (version 1.4) - Document vendor support for this
extension; note that future NVIDIA GPU designs will not support this
extension. (Mark Kilgard)
 |  | Last update: November 14, 2006.
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