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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 )


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.

       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_UNSIGNED_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-dimensional texturing, call glEnable and glDisable with
       argument GL_TEXTURE_2D.

       glTexSubImage2D redefines a contiguous subregion of an existing two-
       dimensional texture image.  The texels referenced by pixels replace the
       portion of the existing texture array with x indices xoffset and
       xoffset + width - 1, inclusive, and y indices yoffset and yoffset +
       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_2max,
       where max is the returned value of GL_MAX_TEXTURE_SIZE.

       GL_INVALID_VALUE is generated if xoffset < - b, (xoffset + 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,
       glCopyTexSubImage2D, glDrawPixels, glPixelStore, glPixelTransfer,
       glTexEnv, glTexGen, glTexImage1D, glTexImage2D, glTexSubImage1D,
       glTexParameter

                                                             GLTEXSUBIMAGE2D()

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