glTexSubImage2DEXT(3G) OpenGL Reference glTexSubImage2DEXT(3G)
NAME
glTexSubImage2DEXT - specify a two-dimensional texture subimage
C SPECIFICATION
void glTexSubImage2DEXT( 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 or
GLDETAILTEXTURE2DSGIS.
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, GLABGREXT, GLLUMINANCE,
GLLUMINANCEALPHA, and GLDEPTHCOMPONENT.
type Specifies the data type of the pixel data. The following
symbolic values are accepted: GLUNSIGNEDBYTE, GLBYTE,
GLBITMAP, GLUNSIGNEDSHORT, GLSHORT, GLUNSIGNEDINT, GLINT,
GLFLOAT, GLUNSIGNEDBYTE332EXT,
GLUNSIGNEDSHORT4444EXT, GLUNSIGNEDSHORT5551EXT,
GLUNSIGNEDINT8888EXT, and GLUNSIGNEDINT1010102EXT.
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. Two-dimensional texturing is
enabled and disabled using glEnable and glDisable with argument
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glTexSubImage2DEXT(3G) OpenGL Reference glTexSubImage2DEXT(3G)
GLTEXTURE2D.
glTexSubImage2DEXT 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
xoffset+width-1, inclusive, and y indices yoffset and yoffset+height-1,
inclusive (But, see discussion of GLINTERLACESGIX below). 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.
When GLINTERLACESGIX is disabled, then counting from zero, each Nth
texel from pixels is assigned to texture array indices [i,j], where i =
xoffset+(N mod width) and j = yoffset+((N div width) mod height).
If GLINTERLACESGIX is enabled, then every other row of the destination
texture is skipped. That is, the destination row for texel N is
yoffset+2((N div width) mod height). A complete video frame may be
assembled in texture memory by invoking glTexSubImage2DEXT on two
consecutive video fields, with yoffset values that differ by one.
NOTES
Texturing has no effect in color index mode.
glPixelStore and glPixelTransfer modes affect texture images in exactly
the way they affect glDrawPixels.
glTexSubImage2DEXT is part of the EXTsubtexture extension.
If type is set to GLUNSIGNEDBYTE332EXT,
GLUNSIGNEDSHORT4444EXT, GLUNSIGNEDSHORT5551EXT,
GLUNSIGNEDINT8888EXT, or GLUNSIGNEDINT1010102EXT and the
EXTpackedpixels extension is not supported then a GLINVALIDENUM error
is generated.
See glIntro for more information on using extensions.
ERRORS
GLINVALIDENUM is generated when target is not one of the allowable
values.
GLINVALIDOPERATION is generated when the texture array has not been
defined by a previous glTexImage2D operation.
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 width < -TEXTURE_BORDER or if
height < -TEXTURE_BORDER, where TEXTURE_BORDER is the border width of the
texture array.
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glTexSubImage2DEXT(3G) OpenGL Reference glTexSubImage2DEXT(3G)
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.
GLINVALIDENUM is generated when format is not an accepted format
constant.
GLINVALIDENUM is generated when type is not a type constant.
GLINVALIDENUM is generated if type is GLBITMAP and format is not
GLCOLORINDEX.
GLINVALIDOPERATION is generated if glTexSubImage2DEXT is executed
between the execution of glBegin and the corresponding execution of
glEnd.
ASSOCIATED GETS
glGetTexImage
glIsEnabled with argument GLTEXTURE2D
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.
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glTexSubImage2DEXT(3G) OpenGL Reference glTexSubImage2DEXT(3G)
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.
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.
SEE ALSO
glDrawPixels, glFog, glPixelStore, glPixelTransfer, glTexEnv, glTexGen,
glTexImage2D, glTexParameter.
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