glCopyTexSubImage2D(3G) OpenGL Reference 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 GLTEXTURE2D
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 GLREADBUFFER (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 format for storage in the texel
array.
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glCopyTexSubImage2D(3G) OpenGL Reference glCopyTexSubImage2D(3G)
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.
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.
ERRORS
GLINVALIDENUM is generated if target is not GLTEXTURE2D.
GLINVALIDOPERATION is generated if the texture array has not been
defined by a previous glTexImage2D or glCopyTexImage2D operation.
GLINVALIDVALUE is generated if level is less than 0.
GLINVALIDVALUE may be generated if level is greater than log max, where
2
max is the returned value of GLMAXTEXTURESIZE.
GLINVALIDVALUE is generated if x < -b or if y < -b, where b is the
border width of the texture array.
GLINVALIDVALUE is generated if xoffset < -b,
(xoffset + width) > (w - b), yoffset < -b, or
(yoffset + height) > (h - b), where w is the GLTEXTUREWIDTH, h is the
GLTEXTUREHEIGHT, and b is the GLTEXTUREBORDER of the texture image
being modified. Note that w and h include twice the border width.
GLINVALIDOPERATION is generated if glCopyTexSubImage2D is executed
between the execution of glBegin and the corresponding execution of
glEnd.
ASSOCIATED GETS
glGetTexImage
glIsEnabled with argument GLTEXTURE2D
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glCopyTexSubImage2D(3G) OpenGL Reference glCopyTexSubImage2D(3G)
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
implementation on O2, and cannot be used on other systems.
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glCopyTexSubImage2D(3G) OpenGL Reference glCopyTexSubImage2D(3G)
SEE ALSO
glCopyPixels, glCopyTexImage1D, glCopyTexImage2D, glCopyTexSubImage1D,
glPixelStore, glPixelTransfer, glTexEnv, glTexGen, glTexImage1D,
glTexImage2D, glTexParameter, glTexSubImage1D, glTexSubImage2D
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