1WGL_NV_render_depth_texture 2http://oss.sgi.com/projects/ogl-sample/registry/NV/render_depth_texture.txt 3 WGL_NO_TEXTURE_ARB 0x2077 4 WGL_BIND_TO_TEXTURE_DEPTH_NV 0x20A3 5 WGL_BIND_TO_TEXTURE_RECTANGLE_DEPTH_NV 0x20A4 6 WGL_DEPTH_TEXTURE_FORMAT_NV 0x20A5 7 WGL_TEXTURE_DEPTH_COMPONENT_NV 0x20A6 8 WGL_DEPTH_COMPONENT_NV 0x20A7 9