glTexImage2D(GL_TEXTURE_RECTANGLE_NV, 0, GL_FLOAT_R16_NV, width, height, GL_LUMINANCE, GL_FLOAT, 0);
 glTexSubImage2D(GL_TEXTURE_RECTANGLE_NV, 0, 0, 0, x, y, GL_LUMINANCE, GL_UNSIGNED_BYTE,
                    yData);