_glCopyTexSubImage2D: copy a two-dimensional texture subimage
- SUB _glCopyTexSubImage2D (BYVAL target AS _UNSIGNED LONG, BYVAL level AS LONG, BYVAL xoffset AS LONG, BYVAL yoffset AS LONG, BYVAL x AS LONG, BYVAL y AS LONG, BYVAL width AS LONG, BYVAL height AS LONG)
- void _glCopyTexSubImage2D(GLenum target, GLint level, GLint xoffset, GLint yoffset, GLint x, GLint y, GLsizei width, GLsizei height);
- Specifies the target texture. Must be _GL_TEXTURE_2D, _GL_TEXTURE_CUBE_MAP_POSITIVE_X, _GL_TEXTURE_CUBE_MAP_NEGATIVE_X, _GL_TEXTURE_CUBE_MAP_POSITIVE_Y, _GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, _GL_TEXTURE_CUBE_MAP_POSITIVE_Z, _GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, or _GL_TEXTURE_1D_ARRAY.
- Specifies the level-of-detail number. Level 0 is the base image level. Level n is the nth mipmap reduction image.
- Specifies a texel offset in the x direction within the texture array.
- 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.
- Specifies the width of the texture subimage.
- Specifies the height of the texture subimage.
_glCopyTexSubImage2D replaces a rectangular portion of a two-dimensional texture image, cube-map texture image or a linear portion of a number of slices of a one-dimensional array texture 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) and with 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.
The pixels in the rectangle are processed exactly as if _glReadPixels 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.
When target is _GL_TEXTURE_1D_ARRAY then the y coordinate and height are treated as the start slice and number of slices to modify.
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.
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.
_glPixelStore modes affect texture images.
_GL_INVALID_ENUM is generated if target is not _GL_TEXTURE_2D, _GL_TEXTURE_CUBE_MAP_POSITIVE_X, _GL_TEXTURE_CUBE_MAP_NEGATIVE_X, _GL_TEXTURE_CUBE_MAP_POSITIVE_Y, _GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, _GL_TEXTURE_CUBE_MAP_POSITIVE_Z, _GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, or _GL_TEXTURE_1D_ARRAY.
_GL_INVALID_VALUE is generated if level is less than 0.
_GL_INVALID_VALUE is generated if xoffset < 0, xoffset + width > w, yoffset < 0, or yoffset + height > h, where w is the _GL_TEXTURE_WIDTH and h is the _GL_TEXTURE_HEIGHT of the texture image being modified.