fglCopyTexSubImage2DEXT man page on IRIX

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fglCopyTexSubImage2DEXT(3G)    OpenGL Reference	   fglCopyTexSubImage2DEXT(3G)

NAME
     fglCopyTexSubImage2DEXT - copy pixels into a 2D texture subimage

FORTRAN SPECIFICATION
     SUBROUTINE fglCopyTexSubImage2DEXT( INTEGER*4 target,
					 INTEGER*4 level,
					 INTEGER*4 xoffset,
					 INTEGER*4 yoffset,
					 INTEGER*4 x,
					 INTEGER*4 y,
					 INTEGER*4 width,
					 INTEGER*4 height )

PARAMETERS
     target   The target texture.  Must be GL_TEXTURE_2D or
	      GL_DETAIL_TEXTURE_2D_SGIS.

     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.

     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
     fglCopyTexSubImage2DEXT 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 fglTexSubImage2DEXT).

     The screen-aligned pixel rectangle with lower-left corner at (x, y)
     having 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.  (But see the paragraph about GL_INTERLACE_SGIX
     below).

     The pixels in the rectangle are processed exactly as if fglCopyPixels 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

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fglCopyTexSubImage2DEXT(3G)    OpenGL Reference	   fglCopyTexSubImage2DEXT(3G)

     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.

     When GL_INTERLACE_READ_INGR is enabled, every other row of the source
     pixel rectangle is read.  The height of the source pixel rectangle is
     equivalent to 2xheight.  Only rows (y+0,y+2,...) of the source are used
     to define the rows of the texture subimage that are affected by the copy.

     When GL_INTERLACE_SGIX is enabled, source pixels are written to every
     other row in the texture subimage, rather than to every successive row.
     The height of the subimage is equivalent to 2xheight.  Rows
     (yoffset+0,yoffset+2,...)	of the destination texture are affected, while
     rows (yoffset+1,yoffset+3,...) are not modified.  A complete video frame
     may be assembled in texture memory by invoking fglCopyTexSubImage2DEXT on
     two consecutive video fields, with yoffset values that differ by one.

NOTES
     fglCopyTexSubImage2DEXT is part of the EXT_copy_texture extension,
     GL_INTERLACE_SGIX is part of the SGIX_interlace extension, and
     GL_INTERLACE_READ_INGR is part of the INGR_interlace_read extension.  See
     fglIntro 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,
     or (yoffset+interlacexheight)>(TEXTURE_HEIGHT-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 fglTexImage2D (or equivalent) operation.

									Page 2

fglCopyTexSubImage2DEXT(3G)    OpenGL Reference	   fglCopyTexSubImage2DEXT(3G)

     GL_INVALID_OPERATION is generated if fglCopyTexSubImage2DEXT is executed
     between the execution of fglBegin and the corresponding execution of
     fglEnd.

ASSOCIATED GETS
     fglGetTexImage

MACHINE DEPENDENCIES
     RealityEngine, RealityEngine2, and VTX systems do not support color
     matrix transformations on images as they are loaded to or read back from
     texture memory.

     RealityEngine, RealityEngine2, and VTX systems support
     fglCopyTexSubImage2D and fglCopyTexSubImage2DEXT with the following
     restrictions:

	  1.  Only level 0 is supported; other levels result in a
	      GL_INVALID_VALUE error.

	  2.  The texel offsets and the dimensions of the subimage must be
	      multiples of 32; otherwise a GL_INVALID_VALUE error is
	      generated.

	  3.  If fglCopyTexSubImage2D or fglCopyTexSubImage2DEXT is used when
	      a GLX video source is the read drawable (see
	      fglXMakeCurrentReadSGI), the X offset and Y offset must both be
	      0 and the subimage width must be 768; otherwise a
	      GL_INVALID_VALUE error is generated.

	  4.  GL_INTERLACE_SGIX is not supported (see fglEnable).

     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, on Octane2
     VPro systems, and on O2 systems.

     The INGR_interlace_read extension is supported only on Octane2 VPro
     systems, and on O2 systems.

									Page 3

fglCopyTexSubImage2DEXT(3G)    OpenGL Reference	   fglCopyTexSubImage2DEXT(3G)

     On O2 systems, when the current read drawable is a DM pbuffer, using
     fglCopyTexSubImage2D or fglCopyTexSubImage2DEXT to copy into a full
     texture image whose dimensions and format match those of the pbuffer
     causes a copy-by-reference.  This has performance advantages, especially
     for video-generated DMbuffers, because it provides a DMA path for
     updating textures.	 Following the copy, rendering to the pbuffer or
     otherwise modifying the DMbuffer, will directly affect texture memory.
     However, this behavior is essentially an unspecified side-effect of the
     implementation on O2, and cannot be used on other systems.

SEE ALSO
     fglTexImage2D, fglTexSubImage2DEXT, fglCopyPixels.

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