Some help is needed. I'm developing drawing application on OpenGL (deployment target 4.0) for iOS (iPad). We have 3 drawing tools: pen, marker (with alfa) and eraser. I draw with textures, using blending in orthographic projection. I can't use z-ordering because in this case I have to face a lot of troubles with cutting and erasing. The thing that I need is to make the pen be always on the top. When I first use marker and than pen - it's ok. But if I use pen first and marker over the pen - I can't see pen color under marker. I'd appreciate any help or advice. Thank you veeeeeery much!