GL_SGIX_shadow

XXX - Not complete yet!!!

Name

	SGIX_shadow

Name Strings

	GL_SGIX_shadow

Version

	$Date: 1997/08/27 19:54:45 $ $Revision: 1.15 $

Number

	34

Dependencies

	None.

Overview

	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

New Tokens

	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

Errors

	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.

New State

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

Implementation Support

   List of OpenGL implementations supporting the GL_SGIX_shadow extension

Original File

   Original text file for the GL_SGIX_shadow extension