Irrlicht Engine

OK, I am making a 3d game, which of course has a HUD display rendered over top everything else. At current I am rendering my HUD every frame to keep it over top of everything else. Is there a way to keep the old rendering of the HUD on top of the new 3d all the time via a 'z index' or something so I only have to redraw the HUD when there are changes to the data displayed?

P.S. my scene is 3d and my HUD is 2d images and text.

Other than rendering your HUD into a texture when it changes and displaying that texture every frame: no.

The 2D overlays are rendered over the 3D scene. Since the 3D scene is rendered first, the HUD will have been overwritten.

Alright, thanks then. It'd be nice if there was a way to omit certain pixels from rendering, or to keep certain things on top, much less requirement on the CPU, but I'll take what I can get. Thanks for answering.