glTexEnv man page on Darwin

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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 environ‐
	       ment 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 sym‐
       bolic name of a texture function.  Four texture functions may be speci‐
       fied: GL_MODULATE, GL_DECAL, GL_BLEND, and GL_REPLACE.

       A  texture  function acts on the fragment to be textured using the tex‐
       ture 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  texture
       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 |  GL_REPLACE  | GL_MODULATE   |
	|     Format	|	       |	       |
	+---------------+--------------+---------------+
	| GL_ALPHA	|C=Cf	       |C=Cf	       |
	|		|A=At	       |A=Af At	       |
	+---------------+--------------+---------------+
	| GL_LUMINANCE	|C=Lt	       |C=CfLt	       |
	|		|A=Af	       |A=Af	       |
	+---------------+--------------+---------------+
	| GL_LUMINANCE_ |C=Lt	       |C=CfLt	       |
	| ALPHA		|A=At	       |A=AfAt	       |
	+---------------+--------------+---------------+
	| GL_INTENSITY	|C=It	       |C=CfIt	       |
	|		|A=It	       |A=AfIt	       |
	+---------------+--------------+---------------+
	| GL_RGB	|C=Ct	       |C=CfCt	       |
	|		|A=Af	       |A=Af	       |
	+---------------+--------------+---------------+
	| GL_RGBA	|C=Ct	       |C=CfCt	       |
	|		|A=At	       |A=AfAt	       |
	+---------------+--------------+---------------+

	+---------------+--------------+---------------+
	| Base Internal |   GL_DECAL   |   GL_BLEND    |
	|     Format	|	       |	       |
	+---------------+--------------+---------------+
	| GL_ALPHA	|undefined     |C=Cf	       |
	|		|	       |A=AfAt	       |
	+---------------+--------------+---------------+
	| GL_LUMINANCE	|undefined     |C=Cf(1-Lt) +   |
	|		|	       |CcLt	       |
	|		|	       |A=Af	       |
	+---------------+--------------+---------------+
	| GL_LUMINANCE_ |undefined     |C=Cf(1-Lt) +   |
	| ALPHA		|	       |CcLt	       |
	|		|	       |A=AfAt	       |
	+---------------+--------------+---------------+
	| GL_INTENSITY	|undefined     |C=Cf(1-It) +   |
	|		|	       |CcIt	       |
	|		|	       |A=Af(1-It) +   |
	|		|	       |AcIt	       |
	+---------------+--------------+---------------+
	| GL_RGB	|C=Ct	       |C=Cf(1-Ct) +   |
	|		|A=Af	       |CcCt	       |
	|		|	       |A=Af	       |
	+---------------+--------------+---------------+
	| GL_RGBA	|C=C(1-At) +   |C=Cf(1-Ct) +   |
	|		|CtAt	       |CcCt	       |
	|		|A=Af	       |A=AfAt	       |
	+---------------+--------------+---------------+

       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, glCopyPixels,  glCopyTexImage1D,  glCopyTexImage2D,
       glCopyTexSubImage1D,	 glCopyTexSubImage2D,	  glCopyTexSubImage3D,
       glTexImage1D,	 glTexImage2D,	    glTexImage3D,      glTexParameter,
       glTexSubImage1D, glTexSubImage2D, glTexSubImage3D

								  GLTEXENV(3G)
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