glCopyTexSubImage3DEXT(3G)

NAME
     glCopyTexSubImage3DEXT - copy pixels into a 3D texture subimage


C SPECIFICATION
     void glCopyTexSubImage3DEXT( GLenum target,
                                  GLint level,
                                  GLint xoffset,
                                  GLint yoffset,
                                  GLint zoffset,
                                  GLint x,
                                  GLint y,
                                  GLsizei width,
                                  GLsizei height )


PARAMETERS
     target   The target texture.  Must be GL_TEXTURE_3D_EXT

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

     xoffset  A texel offset in the x direction within the texture array.

     yoffset  A texel offset in the y direction within the texture array.

     zoffset  A texel offset in the z direction within the texture array.

     x        The x coordinate of the lower-left corner of the pixel rectangle
              to be transferred to the texture array.

     y        The y coordinate of the lower-left corner of the pixel rectangle
              to be transferred to the texture array.

     width    The width of the texture subimage.

     height   The height of the texture subimage.

DESCRIPTION
     glCopyTexSubImage3DEXT replaces a rectangular portion of a three-
     dimensional texture image with pixels from the current GL_READ_BUFFER
     (rather than from main memory, as is the case for glTexSubImage3DEXT).

     The screen-aligned pixel rectangle with lower-left corner at (x, y)
     having width width and height height replaces the rectangular area of the
     S-T slice located at zoffset with  x indices xoffset through
     xoffset+width-1, inclusive, and y indices yoffset through
     yoffset+height-1, inclusive (But, see discussion of GL_INTERLACE_SGIX
     below).

     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 GL_INTERLACE_SGIX is enabled, then every other row of the destination
     texture is skipped. That is, only rows (0,2,4,...) of the S-T slice
     (where the border is considered part of the slice) are defined. A
     complete video frame may be assembled in a slice of the texture array by
     invoking glCopyTexSubImage3DEXT on two consecutive video fields, with
     yoffset values that differ by one.

     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.

     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.

NOTES
     glCopyTexSubImage3DEXT is part of the EXT_copy_texture extension.  See
     glIntro for more information about using extensions.

ERRORS
     GL_INVALID_ENUM is generated when target is not one of the allowable
     values.

     GL_INVALID_VALUE is generated if level is less than zero or greater than
     log (max), where max is the returned value of GL_MAX_TEXTURE_SIZE.
        2

     GL_INVALID_VALUE is generated if xoffset<-TEXTURE_BORDER,
     (xoffset+width)>(TEXTURE_WIDTH-TEXTURE_BORDER), yoffset<-TEXTURE_BORDER,
     (yoffset+interlacexheight)>(TEXTURE_HEIGHT-TEXTURE_BORDER), or if
     zoffset<-TEXTURE_BORDER.  Where TEXTURE_WIDTH, TEXTURE_HEIGHT, and
     TEXTURE_BORDER are the state values of the texture image being modified,
     and interlace is 1 if GL_INTERLACE_SGIX is disabled and 2 otherwise.
     Note that TEXTURE_WIDTH and TEXTURE_HEIGHT include twice the border
     width.

     GL_INVALID_VALUE is generated if width or height is negative.

     GL_INVALID_OPERATION is generated when the texture array has not been
     defined by a previous glTexImage3D (or equivalent) operation.

     GL_INVALID_OPERATION is generated if glCopyTexSubImage3DEXT is executed
     between the execution of glBegin and the corresponding execution of
     glEnd.
ASSOCIATED GETS
     glGetTexImage


MACHINE DEPENDENCIES
     glCopyTexSubImage3DEXT is not supported on RealityEngine, RealityEngine2,
     and VTX systems.

     On InfiniteReality systems, there is a performance benefit when the width
     of the image to be transferred to texture memory is a multiple of 8.

     Texture borders are not supported on InfiniteReality systems.
     Applications should use borderless textures and GL_CLAMP_TO_EDGE_SGIS
     wrap mode.

     On High Impact and Maximum Impact systems, if the right side of the image
     to be transferred to texture memory is not the right side of the texture,
     then its index must be a multiple of 32, where index = xoffset+width.
     Otherwise it will generate a GL_INVALID_VALUE error.

     The SGIX_interlace extension is supported only on InfiniteReality
     systems, on RealityEngine, RealityEngine2, and VTX systems, and on O2
     systems.


SEE ALSO
     glTexImage3D, glTexSubImage3DEXT, glCopyPixels.