glCopyTexSubImage2D

NAME

glCopyTexSubImage2D - copy a two-dimensional texture subimage

C SPECIFICATION

void glCopyTexSubImage2D(GLenum target,
                         GLint level,
                         GLint xoffset,
                         GLint yoffset,
                         GLint x,
                         GLint y,
                         GLsizei width,
                         GLsizei height)

PARAMETERS

target	Specifies the target texture. Must be GL_TEXTURE_2D
level	Specifies the level-of-detail number. Level 0 is the base image level. Level n is the n^th 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.
x, y	Specify the window coordinates of the lower left corner of the rectangular region of pixels to be copied.
width	Specifies the width of the texture subimage.
height	Specifies the height of the texture subimage.

DESCRIPTION

glCopyTexSubImage2D 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 glTexSubImage2D).

The screen-aligned pixel rectangle with lower-left corner at (x,y), width width and height height is used to define the texture image. If GL_INTERLACE_READ_I3D is enabled, every other row is skipped such that the pixel rectangle with lower-left corner at (x,y), width width and height 2 * height - 1 is used to define the texture image. If any pixels within this region are outside the window that is associated with the GL context, the values obtained for those pixels are undefined.

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 are replaced.

If GL_INTERLACE_EXT is enabled, only rows (0,2,4,...) of the texture (where the border is considered part of the texture) are defined. A complete video frame may be assembled in a slice of the texture array by invoking glCopyTexSubImage2D on two consecutive video fields, with yoffset values that differ by one.

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 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.

No change is made to the internalformat, width, height, or border parameters of the specified texture array or to texel values outside the specified subregion.

NOTES

glCopyTexSubImage2D 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.

EXTENSIONS

Some routines and constants for this function are part of an extension, not part of the core GL command set. The following extension names must be present in the string returned by glGetString when called with argument GL_EXTENSIONS to use these routines and constants.

EXT_interlace: GL_INTERLACE_EXT is part of the EXT_interlace extension.
EXT_interlace_read: GL_INTERLACE_READ_I3D is part of the EXT_interlace_read extension.

ERRORS

GL_INVALID_ENUM is generated if target is not GL_TEXTURE_2D.

GL_INVALID_OPERATION is generated if the texture array has not been defined by a previous glTexImage2D or glCopyTexImage2D operation.

GL_INVALID_VALUE is generated if level is less than 0.

GL_INVALID_VALUE may be generated if level is greater than LOG₂(max), where max is the returned value of GL_MAX_TEXTURE_SIZE.

GL_INVALID_VALUE is generated if x < -b or if y < -b, where b is the border width of the texture array.

GL_INVALID_VALUE is generated if xoffset < -b, (xoffset + width) > (w - b), yoffset < -b, or (yoffset + I * height) > (h - b), where w is the GL_TEXTURE_WIDTH, h is the GL_TEXTURE_HEIGHT, b is the border width of the texture image being modified, and I is 2 if GL_INTERLACE_EXT is enabled and 1 otherwise. Note that w and h include twice the border width.

GL_INVALID_OPERATION is generated if glCopyTexSubImage2D is executed between the execution of glBegin and the corresponding execution of glEnd.

ASSOCIATED GETS

glGetTexImage
glIsEnabled with argument GL_TEXTURE_2D