gltexsubimage2dext - Man Page
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 GL_TEXTURE_2D or
GL_DETAIL_TEXTURE_2D_SGIS.
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: GL_COLOR_INDEX, GL_RED, GL_GREEN, GL_BLUE,
GL_ALPHA, GL_RGB, GL_RGBA, GL_ABGR_EXT, GL_LUMINANCE,
GL_LUMINANCE_ALPHA, and GL_DEPTH_COMPONENT.
type Specifies the data type of the pixel data. The following
symbolic values are accepted: GL_UNSIGNED_BYTE, GL_BYTE,
GL_BITMAP, GL_UNSIGNED_SHORT, GL_SHORT, GL_UNSIGNED_INT, GL_INT,
GL_FLOAT, GL_UNSIGNED_BYTE_3_3_2_EXT,
GL_UNSIGNED_SHORT_4_4_4_4_EXT, GL_UNSIGNED_SHORT_5_5_5_1_EXT,
GL_UNSIGNED_INT_8_8_8_8_EXT, and GL_UNSIGNED_INT_10_10_10_2_EXT.
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)
GL_TEXTURE_2D.
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 GL_INTERLACE_SGIX 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 GL_INTERLACE_SGIX 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 GL_INTERLACE_SGIX 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 EXT_subtexture extension.
If type is set to GL_UNSIGNED_BYTE_3_3_2_EXT,
GL_UNSIGNED_SHORT_4_4_4_4_EXT, GL_UNSIGNED_SHORT_5_5_5_1_EXT,
GL_UNSIGNED_INT_8_8_8_8_EXT, or GL_UNSIGNED_INT_10_10_10_2_EXT and the
EXT_packed_pixels extension is not supported then a GL_INVALID_ENUM error
is generated.
See glIntro for more information on using extensions.
ERRORS
GL_INVALID_ENUM is generated when target is not one of the allowable
values.
GL_INVALID_OPERATION is generated when the texture array has not been
defined by a previous glTexImage2D operation.
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 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)
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_ENUM is generated when format is not an accepted format
constant.
GL_INVALID_ENUM is generated when type is not a type constant.
GL_INVALID_ENUM is generated if type is GL_BITMAP and format is not
GL_COLOR_INDEX.
GL_INVALID_OPERATION is generated if glTexSubImage2DEXT is executed
between the execution of glBegin and the corresponding execution of
glEnd.
ASSOCIATED GETS
glGetTexImage
glIsEnabled with argument GL_TEXTURE_2D
MACHINE DEPENDENCIES
RealityEngine, RealityEngine2, and VTX systems do not support convolving
images as they are loaded into texture memory.
InfiniteReality systems have limited support for convolving images as
they are loaded into texture memory. The image resulting from
convolution must be a multiple of 8 in width.
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.
RealityEngine, RealityEngine2, and VTX systems do not support histogram
or minmax operations on images as they are being loaded into texture
memory.
The SGIX_interlace extension is supported only on InfiniteReality systems
and on RealityEngine, RealityEngine2, and VTX systems.
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glTexSubImage2DEXT(3G) OpenGL Reference glTexSubImage2DEXT(3G)
The EXT_packed_pixels extension is not supported on RealityEngine,
RealityEngine2, and VTX systems; it will be supported on High Impact and
Maximum Impact systems in a future release.
GL_DEPTH_COMPONENT textures are a partial implementation of an extension
that will be more fully documented in a subsequent release. They are
supported only on InfiniteReality systems.
On RealityEngine, RealityEngine2, and VTX systems, glTexSubImage2DEXT is
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. glTexSubImage2DEXT may be used only with a texture that was
created using glTexImage2D with a NULL texture image.
3. 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: GL_LUMINANCE and GL_UNSIGNED_BYTE, GL_LUMINANCE and
GL_UNSIGNED_SHORT, GL_LUMINANCE_ALPHA and GL_UNSIGNED_BYTE,
GL_LUMINANCE_ALPHA and GL_UNSIGNED_SHORT, GL_RGB and
GL_UNSIGNED_BYTE and GL_RGBA and GL_UNSIGNED_BYTE. Any other
combination of format and type will result in a GL_INVALID_ENUM
error.
5. Using glTexSubImage2DEXT in conjunction with pixel mapping
results in a GL_INVALID_OPERATION error (see glPixelTransfer and
glPixelMap).
6. glTexSubImage2DEXT may not be used in display lists or when
rendering remotely.
7. GL_INTERLACE_SGIX 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 GL_INVALID_VALUE error.
SEE ALSO
glDrawPixels, glFog, glPixelStore, glPixelTransfer, glTexEnv, glTexGen,
glTexImage2D, glTexParameter.
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