It looks like things may be moving further towards 3D in the PS3 BD-J homebrew scene, as evidenced by the BD-J flight demo released by Nuclear Bit on the QJ.NET PS3 Hacks, Exploits and Homebrew forum.

The BD-J flight demo is based on terrain rendering code originally writtern in C and then rewritten for Java. The developer notes that it uses floats in stead of fixed point arithmetic. It's also in 3D, with Novice Bit going voxel-based instead of working with polygons.

To install the flight demo, just extract the AVCHD folder to a USB storage device of your choice and run it. The flight2 folder contains the source code. The d-pad is used to turn and control speed while the Square and Cross buttons change the viewer's altitude.