extensions/HP/HP_texture_lighting.txt

XXX - incomplete

PRELIMINARY - NOT COMPLETE
--------------------------

Name

    HP_texture_lighting

Name Strings

    GL_HP_texture_lighting

Version

    1.0

Number

    111

Dependencies

    OpenGL 1.1

Overview

    This extension defines a mechanism for applications to request
    that color originating from specular lighting be added to
    the fragment color _after_ texture application.

New Procedures And Functions

    None

New Tokens

    Accepted by the <pname> parameter of TexEnvf, TexEnvfv, TexEnvi,
    TexEnviv:

	TEXTURE_LIGHTING_MODE_HP

    Accepted by the <param> parameter of TexEnvf, TexEnvfv, TexEnvi,
    TexEnviv when <pname> is TEXTURE_APP_MODE_HP:

	TEXTURE_POST_SPECULAR_HP
	TEXTURE_PRE_SPECULAR_HP

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

    Lighting Operation

	If the texture application mode is TEXTURE_POST_SPECULAR_HP, the
	color c produced by lighting a vertex is given by:

	    c	= e
		   cm

		+ a   *  a
		   cm     cs

		  n-1
		+ SUM (att )(spot )[a   * a
		  i=0     i      i   cm    cli

				+   (n @ VP   )d   * d
					   pli  cm    cli

						srm
				+   (f )(n @ h )    s   * s]
				      i       i      cm    cli

	If the texture application mode is TEXTURE_PRE_SPECULAR_HP, and
	if texturing is enabled, two lighting components are computed
	separately per vertex.

	Emissive, ambient, and diffuse color, c   :
					       ead

	    c	= e
	     ead   cm

		+ a   *  a
		   cm     cs

		  n-1
		+ SUM (att )(spot )[a   * a
		  i=0     i      i   cm    cli

				+   (n @ VP   )d   * d]
					   pli  cm    cli

	Specular color, c :
			 s

		  n-1                          srm
	    c	= SUM (att )(spot )(f )(n @ h )    s   * s
	     s	  i=0     i      i   i       i      cm    cli

	These terms are then added after texture application, and the
	final (clamped) color used as the fragment color.


Additions to Chapter 3 of the GL Specification (Rasterization)

			Point
	       +--> Rasterization -->+
               |		     |
      From     |	Line	     |
    Primitive -+--> Rasterization -->+
    Assembly   |                     |
	       |      Polygon        |
	       +--> Rasterization -->+---> Texturing ---> Specular ---> Fog 
				     |
		        Pixel	     |
    DrawPixels --->   Rectangle ---->+
		    Rasterization    |
				     |
			Bitmap	     |
      Bitmap -----> Rasterization -->+

    Figure 3.1, rasterization


    3.8.5 Texture Environments and Texture Functions

	If the texture application mode is TEXTURE_PRE_SPECULAR_HP,
	R , G , and B  refer to c   , the emissive, ambient, and diffuse color.
	 f   f       f           ead

    3.8a Specular

	If the texture application mode is TEXTURE_PRE_SPECULAR_HP and
	texturing is enabled, then the separate specular lighting
	coefficient interpolated for this fragment is added in at this
	stage.  The result is clamped before sending the fragment color
	to subsequent stages.  If the texture application mode is
	TEXTURE_POST_SPECULAR_HP, this stage is not enabled.

Additions to Chapter 4 of the GL Specification (Per-Fragment Operations
and the Framebuffer)

    None

Additions to Chapter 5 of the GL Specification (Special Functions)

    None

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

    Get value		     Type Initial value		    Description		      Sec	 Attribute
    TEXTURE_LIGHTING_MODE_HP  Z4  TEXTURE_POST_SPECULAR_HP  Texture application mode  3.8a	 texture

Additions to the GLX Specification

    None

GLX Protocol

    TBD - ?

Errors

    INVALID_ENUM is generated if the <pname> parameter of TexEnvi,
      TexEnviv, TexEnvf, or TexEnvf is TEXTURE_LIGHTING_MODE_HP and 
      the <param> parameter is not one of TEXTURE_POST_SPECULAR_HP or
      TEXTURE_PRE_SPECULAR_HP.

New State

    None

New Implementation Dependent State

    None