glcopytexsubimage2dext
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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 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
glCopyTexSubImage2DEXT 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 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 GL_INTERLACE_SGIX
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
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_SGIX 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 EXT_copy_texture extension, and
GL_INTERLACE_SGIX is part of the SGIX_interlace 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
log2(max), where max is the returned value of GL_MAX_TEXTURE_SIZE.
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 glTexImage2D (or equivalent) operation.
GL_INVALID_OPERATION 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 support
glCopyTexSubImage2DEXT 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 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 GL_INVALID_VALUE error is generated.
4. GL_INTERLACE_SGIX is not supported (see glEnable).
On InfiniteReality systems, the width of the image to be transferred to
texture memory must be a multiple of 8. This constraint will be lifted
in a future release, though transfers that are a multiple of 8 in length
will have somewhat higher performance than other transfers.
Texture borders are not supported on InfiniteReality systems. They will
be supported in a future release, however, they will require large
amounts of texture memory. Whenever possible, 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
and on RealityEngine, RealityEngine2, and VTX systems.
Note that InfiniteReality systems currently do not support copying
depth-format textures (used for shadow maps) from the framebuffer to
texture memory. This will be fixed in a subsequent release.
SEE ALSO
glTexImage2D, glTexSubImage2DEXT, glCopyPixels.
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