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
Page 1
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_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 glCopyTexSubImage2DEXT on
two consecutive video fields, with yoffset values that differ by one.
NOTES
glCopyTexSubImage2DEXT 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
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,
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.
Page 2
glCopyTexSubImage2DEXT(3G) OpenGL Reference glCopyTexSubImage2DEXT(3G)
GL_INVALID_OPERATION is generated if glCopyTexSubImage2DEXT is executed
between the execution of glBegin and the corresponding execution of
glEnd.
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
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 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 GL_INVALID_VALUE
error is generated.
4. GL_INTERLACE_SGIX 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 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
glCopyTexSubImage2DEXT(3G) OpenGL Reference glCopyTexSubImage2DEXT(3G)
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.
SEE ALSO
glTexImage2D, glTexSubImage2DEXT, glCopyPixels.
Page 4