C SPECIFICATION

       void GLAPIENTRY glCopyTexSubImage2D( GLenum target,
                                            GLint leve )

PARAMETERS

       target  Specifies the target texture.  Must be GL_TEXTURE_2D.

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

       _param3 Specifies a texel offset in the x direction within the  texture
               array.

       _param4 Specifies  a texel offset in the y direction within the texture
               array.

       _param5, _param6
               Specify the window coordinates of the lower left corner of  the
               rectangular region of pixels to be copied.

       _param7 Specifies the width of the texture subimage.

       _param8 Specifies the height of the texture subimage.

DESCRIPTION

       glCopyTexSubImage2D replaces a rectangular portion of a two-dimensional
       texture image with pixels from the current GL_READ_BUFFER (rather  than
       from main memory, as is the case for glTexSubImage2D).

       The   screen-aligned   pixel   rectangle  with  lower  left  corner  at
       (_param5, _param6) and with width _param7 and height  _param8  replaces
       the  portion  of  the  texture  array  with  x  indices _param3 through
       _param3+_param7-1,   inclusive,   and   y   indices   _param4   through
       _param4+_param8-1, inclusive, at the mipmap level specified by leve.

       The  pixels  in  the rectangle are processed exactly as if glCopyPixels
       had been called, but the process stops just  before  final  conversion.
       At  this  point,  all  pixel  component values are clamped to the range
       [0, 1] and then converted to the texture's internal format for  storage
       in the texel array.

       The destination rectangle in the texture array may not include any tex-
       els outside 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.

       If any of the pixels within the  specified  rectangle  of  the  current
       GL_READ_BUFFER  are outside the read window associated with the current
       rendering context, then the values obtained for those pixels are  unde-
       fined.
       When  the  GL_ARB_imaging  extension  is supported, the RGBA components
       read from the framebuffer may be processed  by  the  imaging  pipeline.
       See glTexImage1D for specific details.

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 or glCopyTexImage2D operation.

       GL_INVALID_VALUE is generated if leve is less than 0.

       GL_INVALID_VALUE may be generated if  leve  is  greater  than  log2max,
       where max is the returned value of GL_MAX_TEXTURE_SIZE.

       GL_INVALID_VALUE  is  generated if _param5<-b or if _param6<-b, where b
       is the border width of the texture array.

       GL_INVALID_VALUE       is       generated       if       _eqnparam3<-b,
       (_param3+_param7)>(w-b),  _param4<-b, or (_param4+_param8)>(h-b), where
       w is the GL_TEXTURE_WIDTH, h is the  GL_TEXTURE_HEIGHT, and  b  is  the
       GL_TEXTURE_BORDER of the texture image being modified.  Note that w and
       h include twice the border width.

       GL_INVALID_OPERATION is generated if  glCopyTexSubImage2D  is  executed
       between  the  execution  of  glBegin and the corresponding execution of
       glEnd.

ASSOCIATED GETS

       glGetTexImage
       glIsEnabled with argument GL_TEXTURE_2D

SEE ALSO

       glCopyPixels, glCopyTexImage1D, glCopyTexImage2D,  glCopyTexSubImage1D,
       glCopyTexSubImage3D,   glPixelStore,   glPixelTransfer,   glReadBuffer,
       glTexEnv,   glTexGen,   glTexImage1D,    glTexImage2D,    glTexImage3D,
       glTexParameter, glTexSubImage1D, glTexSubImage2D, glTexSubImage3D



                                                       GLCOPYTEXSUBIMAGE2D(3G)