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GLCOPYTEXSUBIMAGE2D(3G)                                                              GLCOPYTEXSUBIMAGE2D(3G)



NAME
       glCopyTexSubImage2D - copy a two-dimensional texture subimage


C SPECIFICATION
       void glCopyTexSubImage2D( GLenum target,
                                 GLint level,
                                 GLint xoffset,
                                 GLint yoffset,
                                 GLint x,
                                 GLint y,
                                 GLsizei width,
                                 GLsizei height )


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 array.

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

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

       width    Specifies the width of the texture subimage.

       height   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 (x, y) and with width width  and  height
       height  replaces  the portion of the texture array with x indices xoffset through xoffset + width -1,
       inclusive, and y indices yoffset through yoffset+height-1, inclusive, at the mipmap  level  specified
       by level.

       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  for storage in the texel array.

       The  destination  rectangle in the texture array may not include any texels 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 undefined.

       No change is made to the internalformat, width, height, or border parameters of the specified texture
       array or to texel values outside the specified subregion.

NOTES
       glCopyTexSubImage2D 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.

       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 level is less than 0.

       GL_INVALID_VALUE may be generated if level is greater than log2(max), where max is the returned value
       of GL_MAX_TEXTURE_SIZE.

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

       GL_INVALID_VALUE  is  generated  if xoffset < -b, (xoffset + width) >(w - b), yoffset < -b, or (yoff-
       set+height) > (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(3G),    glCopyTexImage1D(3G),    glCopyTexImage2D(3G),   glCopyTexSubImage1D(3G),   glCopyTexSubImage3D(3G),
       glPixelStore(3G),  glPixelTransfer(3G),  glReadBuffer(3G),  glTexEnv(3G),   glTexGen(3G),   glTexImage1D(3G),   glTexImage2D(3G),
       glTexImage3D(3G), glTexParameter(3G), glTexSubImage1D(3G), glTexSubImage2D(3G), glTexSubImage3D(3G)




                                                                                     GLCOPYTEXSUBIMAGE2D(3G)