fglCopyTexSubImage2D(3G)
fglCopyTexSubImage2D - copy a two-dimensional texture subimage
As shipped in IRIX 6.5. First release of IRIX 6.5.
NAME fglCopyTexSubImage2D - copy a two-dimensional texture subimage FORTRAN SPECIFICATION SUBROUTINE fglCopyTexSubImage2D( INTEGER*4 target, INTEGER*4 level, INTEGER*4 xoffset, INTEGER*4 yoffset, INTEGER*4 x, INTEGER*4 y, INTEGER*4 width, INTEGER*4 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 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. 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 fglCopyTexSubImage2D 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 fglTexSubImage2D). 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 fglCopyPixels 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. 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. NOTES fglCopyTexSubImage2D is available only if the GL version is 1.1 or greater. Texturing has no effect in color index mode. fglPixelStore and fglPixelTransfer modes affect texture images in exactly the way they affect fglDrawPixels. 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 fglTexImage2D or fglCopyTexImage2D operation. GL_INVALID_VALUE is generated if level is less than 0. GL_INVALID_VALUE may be generated if level is greater than log max, where 2 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 + height) > (h - b), where w is the GL_TEXTURE_WIDTH, h is the GL_TEXTURE_HEIGHT, and b is the GL_TEXTURE_BORDER of the texture image being modified. Note that w and h include twice the border width. GL_INVALID_OPERATION is generated if fglCopyTexSubImage2D is executed between the execution of fglBegin and the corresponding execution of fglEnd. ASSOCIATED GETS fglGetTexImage fglIsEnabled with argument GL_TEXTURE_2D 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 support fglCopyTexSubImage2D and fglCopyTexSubImage2DEXT with the following restrictions: 1. Only level 0 is supported; other levels result in a GL_INVALID_VALUE error. 2. The texel offsets and the dimensions of the subimage must be multiples of 32; otherwise a GL_INVALID_VALUE error is generated. 3. If fglCopyTexSubImage2D or fglCopyTexSubImage2DEXT is used when a GLX video source is the read drawable (see fglXMakeCurrentReadSGI), the X offset and Y offset must both be 0 and the subimage width must be 768; otherwise a GL_INVALID_VALUE error is generated. 4. GL_INTERLACE_SGIX is not supported (see fglEnable). 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 GL_CLAMP_TO_EDGE_SGIS wrap mode. 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. The SGIX_interlace extension is supported only on InfiniteReality systems, on RealityEngine, RealityEngine2, and VTX systems, and on O2 systems. On O2 systems, when the current read drawable is a DM pbuffer, using fglCopyTexSubImage2D or fglCopyTexSubImage2DEXT to copy into a full texture image whose dimensions and format match those of the pbuffer causes a copy-by-reference. This has performance advantages, especially for video-generated DMbuffers, because it provides a DMA path for updating textures. Following the copy, rendering to the pbuffer or otherwise modifying the DMbuffer, will directly affect texture memory. However, this behavior is essentially an unspecified side-effect of the implementation on O2, and cannot be used on other systems. SEE ALSO fglCopyPixels, fglCopyTexImage1D, fglCopyTexImage2D, fglCopyTexSubImage1D, fglPixelStore, fglPixelTransfer, fglTexEnv, fglTexGen, fglTexImage1D, fglTexImage2D, fglTexParameter, fglTexSubImage1D, fglTexSubImage2D