GLTEXENV(3G)															      GLTEXENV(3G)

NAME

       glTexEnvf, glTexEnvi, glTexEnvfv, glTexEnviv - set texture environment parameters

C SPECIFICATION

       void glTexEnvf( GLenum target,
		       GLenum pname,
		       GLfloat param )
       void glTexEnvi( GLenum target,
		       GLenum pname,
		       GLint param )

PARAMETERS

       target  Specifies a texture environment.  Must be GL_TEXTURE_ENV.

       pname   Specifies the symbolic name of a single-valued texture environment parameter.  Must be GL_TEXTURE_ENV_MODE.

       param   Specifies a single symbolic constant, one of GL_MODULATE, GL_DECAL, GL_BLEND, or GL_REPLACE.

C SPECIFICATION

       void glTexEnvfv( GLenum target,
			GLenum pname,
			const GLfloat *params )
       void glTexEnviv( GLenum target,
			GLenum pname,
			const GLint *params )

PARAMETERS

       target Specifies a texture environment.	Must be GL_TEXTURE_ENV.

       pname  Specifies the symbolic name of a texture environment parameter.  Accepted values are GL_TEXTURE_ENV_MODE and GL_TEXTURE_ENV_COLOR.

       params Specifies a pointer to a parameter array that contains either a single symbolic constant or an RGBA color.

DESCRIPTION

       A  texture environment specifies how texture values are interpreted when a fragment is textured.  target must be GL_TEXTURE_ENV.  pname can
       be either GL_TEXTURE_ENV_MODE or GL_TEXTURE_ENV_COLOR.

       If pname is GL_TEXTURE_ENV_MODE, then params is (or points to) the symbolic name of a texture function.	 Four  texture	functions  may	be
       specified: GL_MODULATE, GL_DECAL, GL_BLEND, and GL_REPLACE.

       A  texture function acts on the fragment to be textured using the texture image value that applies to the fragment (see glTexParameter) and
       produces an RGBA color for that fragment.  The following table shows how the RGBA color is produced for each of the three texture functions
       that  can  be chosen.  C is a triple of color values (RGB) and A is the associated alpha value.	RGBA values extracted from a texture image
       are in the range [0,1].	The subscript f refers to the incoming fragment, the subscript t to the texture image, the subscript c to the tex-
       ture environment color, and subscript v indicates a value produced by the texture function.

       A  texture  image  can  have up to four components per texture element (see glTexImage1D, glTexImage2D, glTexImage3D, glCopyTexImage1D, and
       glCopyTexImage2D).  In a one-component image, Lt indicates that single component.  A two-component image uses Lt and At.  A three-component
       image has only a color value, Ct.  A four-component image has both a color value Ct and an alpha value At.

					  ----------------------------------------------------------------------
					  Base internal 		Texture functions
							  GL_MODULATE	 GL_DECAL	GL_BLEND     GL_REPLACE
					  ----------------------------------------------------------------------
					    GL_ALPHA	     Cv=Cf	 undefined	 Cv=Cf	       Cv=Cf
							    Av=AfAt			 Av=Af	       Av=At
					  ----------------------------------------------------------------------

					  GL_LUMINANCE	    Cv=LtCf	 undefined    Cv=(1-Lt)Cf      Cv=Lt
											 +LtCc
						1	     Av=Af			  Av=Af        Av=Af
					  ----------------------------------------------------------------------
					  GL_LUMINANCE	    Cv=LtCf	 undefined    Cv=(1-Lt)Cf      Cv=Lt
					    f3_ALPHA					  +LtCc
						2	    Av=AtAf			Av=AtAf        Av=At
					  ----------------------------------------------------------------------
					  GL_INTENSITY	    Cv=CfIt	 undefined    Cv=(1-It)Cf      Cv=It
											 +ItCc
					       c	    Av=AfIt		      Av=(1-It)Af      Av=It
											 +ItAc
					  ----------------------------------------------------------------------
					     GL_RGB	    Cv=CtCf	   Cv=Ct      Cv=(1-Ct)Cf      Cv=Ct
											  +CtCc
						3	     Av=Af	   Av=Af	 Av=Af	       Av=Af
					  ----------------------------------------------------------------------
					     GL_RGBA	    Cv=CtCf	Cv=(1-At)Cf   Cv=(1-Ct)Cf      Cv=Ct
									   +AtCt	  +CtCc
						4	    Av=AtAf	   Av=Af	Av=AtAf        Av=At
					  ----------------------------------------------------------------------
       If pname is GL_TEXTURE_ENV_COLOR, params is a pointer to an array that holds an RGBA color consisting of four values.  Integer color compo-
       nents are interpreted linearly such that the most positive integer maps to 1.0, and the most negative integer maps to -1.0.  The values are
       clamped to the range [0,1] when they are specified.  Cc takes these four values.

       GL_TEXTURE_ENV_MODE defaults to GL_MODULATE and GL_TEXTURE_ENV_COLOR defaults to (0, 0, 0, 0).

NOTES

       GL_REPLACE may only be used if the GL version is 1.1 or greater.

       Internal formats other than 1, 2, 3, or 4 may only be used if the GL version is 1.1 or greater.

       When  the  GL_ARB_multitexture  extension  is  supported,  glTexEnv  controls  the texture environment for the current active texture unit,
       selected by glActiveTextureARB.	GL_INVALID_ENUM is generated when target or pname is not one of  the  accepted	defined  values,  or  when
       params should have a defined constant value (based on the value of pname) and does not.

       GL_INVALID_OPERATION is generated if glTexEnv is executed between the execution of glBegin and the corresponding execution of glEnd.

ASSOCIATED GETS

       glGetTexEnv

SEE ALSO

       glActiveTextureARB(3G),	glCopyPixels(3G),  glCopyTexImage1D(3G),  glCopyTexImage2D(3G),  glCopyTexSubImage1D(3G), glCopyTexSubImage2D(3G),
       glCopyTexSubImage3D(3G),     glTexImage1D(3G),	  glTexImage2D(3G),	glTexImage3D(3G),     glTexParameter(3G),     glTexSubImage1D(3G),
       glTexSubImage2D(3G), glTexSubImage3D(3G)

																      GLTEXENV(3G)