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GLTEXSUBIMAGE2D()					       GLTEXSUBIMAGE2D()

NAME
     glTexSubImage2D - specify a two-dimensional texture subimage

C SPECIFICATION
     void glTexSubImage2D( GLenum target,
			   GLint level,
			   GLint xoffset,
			   GLint yoffset,
			   GLsizei width,
			   GLsizei height,
			   GLenum format,
			   GLenum type,
			   const GLvoid *pixels )

     delim $$

PARAMETERS
     target   Specifies the target texture.  Must be GL_TEXTURE_2D.

     level    Specifies  the  level-of-detail number.  Level 0 is the base image
	      level.  Level n is the nth mipmap reduction image.

     xoffset  Specifies a texel offset in the x direction within the texture ar-
	      ray.

     yoffset  Specifies a texel offset in the y direction within the texture ar-
	      ray.

     width    Specifies the width of the texture subimage.

     height   Specifies the height of the texture subimage.

     format   Specifies the format of the pixel data.	The  following	symbolic
	      values  are  accepted:  GL_COLOR_INDEX, GL_RED, GL_GREEN, GL_BLUE,
	      GL_ALPHA, GL_RGB, GL_RGBA, GL_LUMINANCE, and GL_LUMINANCE_ALPHA.

     type     Specifies the data type of the pixel data.  The following symbolic
	      values are accepted: GL_UNSIGNED_BYTE, GL_BYTE, GL_BITMAP,  GL_UN-
	      SIGNED_SHORT, GL_SHORT, GL_UNSIGNED_INT, GL_INT, and GL_FLOAT.

     pixels   Specifies a pointer to the image data in memory.

DESCRIPTION
     Texturing	maps  a portion of a specified texture image onto each graphical
     primitive for which texturing is enabled.	To enable and disable two-dimen-
     sional texturing, call glEnable and glDisable with argument GL_TEXTURE_2D.

     glTexSubImage2D redefines a contiguous subregion of an existing  two-dimen-
     sional  texture image.  The texels referenced by pixels replace the portion
     of  the  existing	texture  array	with  x  indices  xoffset  and	 $"xoff-
     set"~+~"width"~-~1$,   inclusive,	 and   y  indices  yoffset  and  $"yoff-
     set"~+~"height"~-~1$, inclusive.  This region may not  include  any  texels
     outside  the range of the texture array as it was originally specified.  It
     is not an error to specify a subtexture with zero width or height, but such
     a specification has no effect.

NOTES
     glTexSubImage2D is available only if the GL version is 1.1 or greater.

     Texturing has no effect in color index mode.

     glPixelStore and glPixelTransfer modes affect texture images in exactly the
     way they affect glDrawPixels.

ERRORS
     GL_INVALID_ENUM is generated if target is not GL_TEXTURE_2D.

     GL_INVALID_OPERATION is generated if the texture array has not been defined
     by a previous glTexImage2D operation.

     GL_INVALID_VALUE is generated if level is less than 0.

     P GL_INVALID_VALUE may be generated if  level  is	greater  than  $log  sub
     2$max, where max is the returned value of GL_MAX_TEXTURE_SIZE.

     GL_INVALID_VALUE	is   generated	 if   $"xoffset"   ~<~	 ~-b$,	$("xoff-
     set"~+~"width") ~>~ (w~-~b)$,  $"yoffset"	~<~  ~-b$,  or	$("yoffset"  ~+~
     "height")	~>~  (h~-~b)$.	 Where	$w$  is the GL_TEXTURE_WIDTH, $h$ is the
     GL_TEXTURE_HEIGHT, and $b$ is the border width of the texture  image  being
     modified.	Note that $w$ and $h$ include twice the border width.

     GL_INVALID_VALUE is generated if width or height is less than 0.

     GL_INVALID_ENUM is generated if format is not an accepted format constant.

     GL_INVALID_ENUM is generated if type is not a type constant.

     GL_INVALID_ENUM  is  generated  if  type  is  GL_BITMAP  and  format is not
     GL_COLOR_INDEX.

     GL_INVALID_OPERATION is generated if glTexSubImage2D  is  executed  between
     the execution of glBegin and the corresponding execution of glEnd.

ASSOCIATED GETS
     glGetTexImage
     glIsEnabled with argument GL_TEXTURE_2D

SEE ALSO
     glCopyTexImage1D,	glCopyTexImage2D,  glCopyTexSubImage1D,  glCopyTexSubIm-
     age2D, glDrawPixels, glPixelStore, glPixelTransfer, glTexEnv, glTexGen, gl-
     TexImage1D, glTexImage2D, glTexSubImage1D, glTexParameter

							       GLTEXSUBIMAGE2D()

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