I have 2 textures (ground and sky images) and a 2-bit mask how to blend them. How should i do it without changing textures? Standard way is to draw one, then draw mask with (GL_DST_COLOR, GL_ZERO) and then draw third with (GL_ONE, GL_ONE), but the third texture needs to be blended with mask inversion. Maybe, there is a way to do this trick without modifying third texture? I need to modify mask dynamically and i don''t want to modify two textures. Thanks