HP Workstation zx2000 OpenGL 1.1 Reference for HP-UX 11.x - Page 82

C glCopyTexSubImage2D glCopyTexSubImage2D glCopyTexSubImage2D: copy a two-dimensional texture sub image. C Specification void glCopyTexSubImage2D( GLenum target, GLint level, GLint xoffset, GLint yoffset, GLint x, GLint y, GLsizei width, GLsizei height) Parameters target level xoffset yoffset x, y width height Specifies the target texture. Must be GL_TEXTURE_2D 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. Specify the window coordinates of the lower left corner of the rectangular region of pixels to be copied. Specifies the width of the texture sub image. Specifies the height of the texture sub image. 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) 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 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. 82 Chapter 3