You can increase the "rays" variable, but you'll have to do some other tweaks to make it all look right. In the C2 version it starts to get bogged down faster with more rays. I'm working on an update now that fixes the horizontal fish-eye and updates how objects are rendered along with some other fixes / features like textured floors and ceilings (using the Mode7 effect plugin). It needs some clean up so that you should be able to increase the resolution with just one variable and have everything else kinda fall in line.