glCopyTexSubImage2DEXT(3G) OpenGL Reference glCopyTexSubImage2DEXT(3G)
NAME
glCopyTexSubImage2DEXT - copy pixels into a 2D texture subimage
C SPECIFICATION
void glCopyTexSubImage2DEXT( GLenum target,
GLint level,
GLint xoffset,
GLint yoffset,
GLint x,
GLint y,
GLsizei width,
GLsizei height )
PARAMETERS
target The target texture. Must be GLTEXTURE2D or
GLDETAILTEXTURE2DSGIS.
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
glCopyTexSubImage2DEXT replaces a rectangular portion of a two-
dimensional texture image with pixels from the current GLREADBUFFER
(rather than from main memory, as is the case for glTexSubImage2DEXT).
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 GLINTERLACESGIX
below).
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
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glCopyTexSubImage2DEXT(3G) OpenGL Reference glCopyTexSubImage2DEXT(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
GLREADBUFFER are outside the read window associated with the current
rendering context, then the values obtained for those pixels are
undefined.
When GLINTERLACESGIX is enabled, successive rows of source pixels are
written to every other row in the texture subimage, rather than to every
successive row. That is, row j or the source image is written to row
yoffset+2j of the destination texture, while rows
(yoffset+1,yoffset+3,...) are not modified. A complete video frame may
be assembled in texture memory by invoking glCopyTexSubImage2DEXT on two
consecutive video fields, with yoffset values that differ by one.
NOTES
glCopyTexSubImage2DEXT is part of the EXTcopytexture extension, and
GLINTERLACESGIX is part of the SGIXinterlace extension. See glIntro
for more information about using extensions.
ERRORS
GLINVALIDENUM is generated when target is not one of the allowable
values.
GLINVALIDVALUE is generated if level is less than zero or greater than
log (max), where max is the returned value of GLMAXTEXTURESIZE.
2
GLINVALIDVALUE 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 GLINTERLACESGIX
is disabled and 2 otherwise. Note that TEXTURE_WIDTH and TEXTURE_HEIGHT
include twice the border width.
GLINVALIDVALUE is generated if width or height is negative.
GLINVALIDOPERATION is generated when the texture array has not been
defined by a previous glTexImage2D (or equivalent) operation.
GLINVALIDOPERATION is generated if glCopyTexSubImage2DEXT is executed
between the execution of glBegin and the corresponding execution of
glEnd.
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glCopyTexSubImage2DEXT(3G) OpenGL Reference glCopyTexSubImage2DEXT(3G)
ASSOCIATED GETS
glGetTexImage
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
glCopyTexSubImage2D and glCopyTexSubImage2DEXT with the following
restrictions:
1. Only level 0 is supported; other levels result in a
GLINVALIDVALUE error.
2. The texel offsets and the dimensions of the subimage must be
multiples of 32; otherwise a GLINVALIDVALUE error is
generated.
3. If glCopyTexSubImage2D or glCopyTexSubImage2DEXT is used when a
GLX video source is the read drawable (see
glXMakeCurrentReadSGI), the X offset and Y offset must both be 0
and the subimage width must be 768; otherwise a GLINVALIDVALUE
error is generated.
4. GLINTERLACESGIX is not supported (see glEnable).
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 GLCLAMPTOEDGESGIS
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 GLINVALIDVALUE error.
The SGIXinterlace extension is supported only on InfiniteReality
systems, on RealityEngine, RealityEngine2, and VTX systems, and on O2
systems.
On O2 systems, when the current read drawable is a DM pbuffer, using
glCopyTexSubImage2D or glCopyTexSubImage2DEXT 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
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glCopyTexSubImage2DEXT(3G) OpenGL Reference glCopyTexSubImage2DEXT(3G)
implementation on O2, and cannot be used on other systems.
SEE ALSO
glTexImage2D, glTexSubImage2DEXT, glCopyPixels.
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