glTexSubImage2D(3G) OpenGL Reference glTexSubImage2D(3G)
NAME
glTexSubImage2D - specify a two-dimensional texture subimage
C SPECIFICATION
void glTexSubImage2D( GLenum target,
GLint level,
GLint xoffset,
GLint yoffset,
GLsizei width,
GLsizei height,
GLenum format,
GLenum type,
const GLvoid *pixels )
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.
width Specifies the width of the texture subimage.
height Specifies the height of the texture subimage.
format Specifies the format of the pixel data. The following symbolic
values are accepted: GLCOLORINDEX, GLRED, GLGREEN, GLBLUE,
GLALPHA, GLRGB, GLRGBA, GLLUMINANCE, and GLLUMINANCEALPHA.
type Specifies the data type of the pixel data. The following
symbolic values are accepted: GLUNSIGNEDBYTE, GLBYTE,
GLBITMAP, GLUNSIGNEDSHORT, GLSHORT, GLUNSIGNEDINT, GLINT,
and GLFLOAT.
pixels Specifies a pointer to the image data in memory.
DESCRIPTION
Texturing maps a portion of a specified texture image onto each graphical
primitive for which texturing is enabled. To enable and disable two-
dimensional texturing, call glEnable and glDisable with argument
GLTEXTURE2D.
glTexSubImage2D redefines a contiguous subregion of an existing two-
dimensional texture image. The texels referenced by pixels replace the
portion of the existing texture array with x indices xoffset and
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glTexSubImage2D(3G) OpenGL Reference glTexSubImage2D(3G)
xoffset + width - 1, inclusive, and y indices yoffset and
yoffset + height - 1, inclusive. This region may not include any texels
outside the range of 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.
NOTES
glTexSubImage2D 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.
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 do not support convolving
images as they are loaded into texture memory.
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.
RealityEngine, RealityEngine2, and VTX systems do not support histogram
or minmax operations on images as they are being loaded into texture
memory.
The SGIXinterlace extension is supported only on InfiniteReality
systems, on RealityEngine, RealityEngine2, and VTX systems, and on O2
systems.
The EXTpackedpixels extension is not supported on RealityEngine,
RealityEngine2, and VTX systems.
On RealityEngine, RealityEngine2, and VTX systems, glTexSubImage2D and
glTexSubImage2DEXT are supported with the following restrictions:
1. Performance is significantly better if the texture subimage X
offset, Y offset, width and height are multiples of 32.
2. glTexSubImage2D and glTexSubImage2DEXT may be used only with a
texture that was created using glTexImage2D with a NULL texture
image.
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glTexSubImage2D(3G) OpenGL Reference glTexSubImage2D(3G)
3. glTexSubImage2D and glTexSubImage2DEXT may not be used with a
mipmap texture. Only level 0 is supported.
4. Only the following texel format and type combinations are
supported: GLLUMINANCE and GLUNSIGNEDBYTE, GLLUMINANCE and
GLUNSIGNEDSHORT, GLLUMINANCEALPHA and GLUNSIGNEDBYTE,
GLLUMINANCEALPHA and GLUNSIGNEDSHORT, GLRGB and
GLUNSIGNEDBYTE and GLRGBA and GLUNSIGNEDBYTE. Any other
combination of format and type will result in a GLINVALIDENUM
error.
5. Using glTexSubImage2D or glTexSubImage2DEXT in conjunction with
pixel mapping results in a GLINVALIDOPERATION error (see
glPixelTransfer and glPixelMap).
6. glTexSubImage2D and glTexSubImage2DEXT may not be used in
display lists or when rendering remotely.
7. GLINTERLACESGIX is not supported (see glEnable).
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.
ERRORS
GLINVALIDENUM is generated if target is not GLTEXTURE2D.
GLINVALIDOPERATION is generated if the texture array has not been
defined by a previous glTexImage2D operation.
GLINVALIDVALUE is generated if level is less than 0.
P GLINVALIDVALUE may be generated if level is greater than log max,
2
where max is the returned value of GLMAXTEXTURESIZE.
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 border width of the texture image being
modified. Note that w and h include twice the border width.
GLINVALIDVALUE is generated if width or height is less than 0.
GLINVALIDENUM is generated if format is not an accepted format
constant.
GLINVALIDENUM is generated if type is not a type constant.
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glTexSubImage2D(3G) OpenGL Reference glTexSubImage2D(3G)
GLINVALIDENUM is generated if type is GLBITMAP and format is not
GLCOLORINDEX.
GLINVALIDOPERATION is generated if glTexSubImage2D is executed between
the execution of glBegin and the corresponding execution of glEnd.
ASSOCIATED GETS
glGetTexImage
glIsEnabled with argument GLTEXTURE2D
SEE ALSO
glCopyTexImage1D, glCopyTexImage2D, glCopyTexSubImage1D,
glCopyTexSubImage2D, glDrawPixels, glPixelStore, glPixelTransfer,
glTexEnv, glTexGen, glTexImage1D, glTexImage2D, glTexSubImage1D,
glTexParameter
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