extensions/IGLOO/IGLOO_viewport_offsetXXX.txt

XXX - Obsolete; implemented as part of GL_SGIX_igloo_interface

Name

    IGLOO_viewport_offsetXXX

    This not an EXT, SGI, SGIS, or SGIX extension. It violates the prefix rules.
    Also the XXX violates the no-caps in the body of the name rule.

Name Strings

    GL_IGLOO_viewport_offsetXXX

    These strings should never be returned by glGetString,
    because I don't expect the get in this  extension to be implemented
    The extension should remain incomplete.
    The name string here is used solely in the registry.

Version

    $Date: 1999/04/03 08:40:52 $ $Revision: 1.2 $

Number

    None

    Do we number these???


Dependencies


    This extension has *NO* dependencies.

Overview

    When Viewport_Offset is enabled then the viewport transformation is becomes


    x_w = (p_x/2) x_d + o_x + 0.5
    y_w = (p_y/2) y_d + o_y + 0.5
    z_w = . . . same as before.

    I believe that this is only useful for emulating IrisGL on top of OpenGL.


New Procedures and Functions


    There are no new Procedures for this extension
New Tokens

*	This list should be complete.  It should separate the new tokens
*	based on which procedures and parameters accept them, and explicitly
*	list those procedures and parameters.  Token suffixes must match the
*	prefix chosen for the extension name.  For example:
*
*	Accepted by the <pname> parameters of GetBooleanv, GetIntegerv,
*	GetFloatv, and GetDoublev:
*
*	    NEW_TOKEN_SGI

    IGLOO_OFFSET_VIEWPORT_XXX Is accepted by glEnable and glDisable.

    Probably not accepted by the <pname> parameter of glGetBooleanv, and
    glIsEnabled.

    (I do not expect glGet to accept this in most implementations,
    but techically it should since this is user state.)

    If glEnable or glDisable generates an INVALID_ENUM then
    this extension is not available.

Additions to Chapter 2 of the 1.0 Specification (OpenGL Operation)



    Section 2.9.1  (Controlling the viewport)
    now reads:

    "The vertex's window coordinates, (x_w) are given by
				      (y_w)
				      (z_w),

    (x_w)   ((p_x/2)x_d + o_x + offset)     )
    (y_w) = ((p_y/2)y_d + o_y + offset)     )
    (z_w)   ([unchanged from versions 1.0]) )

    where offset equals 0.5 if IGLOO_OFFSET_VIEWPORT_XXX is enabled, and 0.0 if it is
    disabled.

Additions to Chapter 3 of the 1.0 Specification (Rasterization)

    NONE

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)

*	List commands that are not included in display lists (typically Get*
*	commands)

    glGet(IGLOO_OFFSET_VIEWPORT_XXX)  will probably not be part of any real implementation.
    glEnable is already display listable and remains so.

Additions to Chapter 6 of the 1.0 Specification (State and State Requests)


   There is one new bit of state.
   This bit is TRUE if IGLOO_OFFSET_VIEWPORT_XXX is enabled
   and FALSE otherwise.  While this is technically user state, it is not
   needed by IGLOO. . .
   It's default value is FALSE.

Additions to the GLX Specification
    No additions are needed for the GLX Specification

Errors
    There is no new Error state, but glEnable/glDisable now accepts a the new token.



New State

*	Description of all state values in table format.  Note that client
*	state should have "client" listed in the Attrib column.

								Initial
    Get Value				Get Command	Type	Value	Attrib
    ---------				-----------	----	------- ------
    IGLOO_OFFSET_VIEWPORT_XXX		glGetBooleanv	Bool	FALSE	enable