This plugin allows impact to render in pseudo 3D like Wolfenstein 3D. It leaves everything intact, so you can write your normal impact entities and plugins.
I included some sample entities and a sample level from my 7dfps attempt Attack of the Gorillas. If you want to see this plugin in action, look here: http://bureaubureau.de/article/attack_of_the_gorilla/
You can get the code and some instructions here: https://github.com/Houly/Impact-Pseudo-3D