   XXX - Not complete yet!!! |
SGIX_shadow
GL_SGIX_shadow
$Date: 1997/08/27 19:54:45 $ $Revision: 1.15 $
$Id: //sw/main/docs/OpenGL/specs/GL_SGIX_shadow.txt#4 $
34
None.
This extension defines two new operations to be performed
on texture values before they are passed on to the filtering
subsystem. These operations perform either a <= or >= test
on the value from texture memory and the iterated R value,
and return 1.0 or 0.0 if the test passes or fails, respectively.
| New Procedures and Functions |
None
Accepted by the <pname> parameter of TexParameterf, TexParameteri,
TexParameterfv, TexParameteriv, GetTexParameterfv, and
GetTexParameteriv, with the <pname> parameter of TRUE or FALSE:
TEXTURE_COMPARE_SGIX
Accepted by the <pname> parameter of TexParameterf, TexParameteri,
TexParameterfv, TexParameteriv, GetTexParameterfv, and
GetTexParameteriv:
TEXTURE_COMPARE_OPERATOR_SGIX
Accepted by the <param> parameter of TexParameterf and
TexParameteri, and by the <params> parameter of TexParameterfv
and TexParameteriv, when their <pname> parameter is
TEXTURE_COMPARE_OPERATOR_SGIX:
TEXTURE_LEQUAL_R_SGIX
TEXTURE_GEQUAL_R_SGIX
| Additions to Chapter 2 of the 1.0 Specification (OpenGL Operation) |
None
| Additions to Chapter 3 of the 1.0 Specification (Rasterization) |
XXX - lots
GL Specification Table 3.8 is updated as follows:
Name Type Legal Values
---- ---- ------------
TEXTURE_WRAP_S integer CLAMP, REPEAT
TEXTURE_WRAP_T integer CLAMP, REPEAT
TEXTURE_WRAP_R_EXT integer CLAMP, REPEAT
TEXTURE_MIN_FILTER integer NEAREST, LINEAR,
NEAREST_MIPMAP_NEAREST,
NEAREST_MIPMAP_LINEAR,
LINEAR_MIPMAP_NEAREST,
LINEAR_MIPMAP_LINEAR,
FILTER4_SGIS,
LINEAR_CLIPMAP_LINEAR_SGIX
TEXTURE_MAG_FILTER integer NEAREST, LINEAR,
FILTER4_SGIS,
LINEAR_DETAIL_SGIS,
LINEAR_DETAIL_ALPHA_SGIS,
LINEAR_DETAIL_COLOR_SGIS,
LINEAR_SHARPEN_SGIS,
LINEAR_SHARPEN_ALPHA_SGIS,
LINEAR_SHARPEN_COLOR_SGIS,
TEXTURE_BORDER_COLOR 4 floats any 4 values in [0,1]
DETAIL_TEXTURE_LEVEL_SGIS integer any non-negative integer
DETAIL_TEXTURE_MODE_SGIS integer ADD, MODULATE
TEXTURE_MIN_LOD_SGIS float any value
TEXTURE_MAX_LOD_SGIS float any value
TEXTURE_BASE_LEVEL_SGIS integer any non-negative integer
TEXTURE_MAX_LEVEL_SGIS integer any non-negative integer
GENERATE_MIPMAP_SGIS boolean TRUE or FALSE
TEXTURE_CLIPMAP_OFFSET_SGIX 2 floats any 2 values
TEXTURE_COMPARE_SGIX boolean TRUE or FALSE
TEXTURE_COMPARE_OPERATOR_SGIX integer TEXTURE_LEQUAL_R_SGIX,
TEXTURE_GEQUAL_R_SGIX
Table 3.8: Texture parameters and their values.
Notes:
* Two new texture operators are defined which alter the sampled
texture values before they are filtered. These operators are
defined only for textures with internal format DEPTH_COMPONENT
or DEPTH_COMPONENTS*_SGI.
* The new operators compare the sample texel value to the value
of the third texture coordinate, R. The texture components are
treated as though they range from 0.0 through 1.0. The value
of the test is zero if the test fails, and one if it passes.
* The test for operator TEXTURE_LEQUAL_R_SGIX passes if the texel
value is less than or equal to R. The test for operator
TEXTURE_GEQUAL_R_SGIX passes if the texel value is greater than
or equal to R.
* The modified texels (with value 0.0 or 1.0 depending on the
test result) are treated as if the texture internal format were
LUMINANCE.
| Additions to Chapter 4 of the 1.0 Specification (Per-Fragment Operations and the Frame Buffer) |
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) |
The texture compare operator is queried by calling
GetTexParameteriv and GetTexParameterfv with <pname> set to
TEXTURE_COMPARE_OPERATOR_SGIX. Texture compare enable/disable
state is queried by calling GetTexParameteriv or GetTexParameterif
with <pname> TEXTURE_COMPARE_SGIX.
| Additions to the GLX Specification |
None
INVALID_OPERATION is generated if TexParameter[if] parameter
<pname> is TEXTURE_COMPARE_OPERATOR_SGIX and parameter <param>
is not TEXTURE_LEQUAL_R_SGIX,or TEXTURE_GEQUAL_R_SGIX.
Get Value Get Command Type Initial Value Attribute
--------- ----------- ---- ------------- ---------
TEXTURE_COMPARE_SGIX GetTexParameter[if]v B False texture
TEXTURE_COMPARE_OPERATOR_SGIX GetTexParameter[if]v Z_2 TEXTURE_LEQUAL_R_SGIX texture
| New Implementation Dependent State |
None
NVIDIA Implementation Details
The specification is unclear if the R texture coordinate is
clamped to the range [0,1]. NVIDIA hardware supporting this
extension does clamp the R texture coordinate to the range [0,1]
on a per-fragment basis.
The behavior of the NV_register_combiners SIGNED_NEGATE_NV mapping
mode is undefined when used to map the initial value of a texture
register corresponding to an enabled texture with a base internal
format of GL_DEPTH_COMPONENT and a true TEXTURE_COMPARE_SGIX
mode when multiple enabled textures have different values for
TEXTURE_COMPARE_OPERATOR_SGIX. . Values subsequently assigned
to such registers and then mapped with SIGNED_NEGATIE_NV operate
as expected.
 |  | Last update: November 14, 2006.
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