The problem is scanning the scene and building a list of visible objects for each x,y,z map grid position. I have done something like this with linepick, but compilation is painfully slow.
I see. How slow is slow? And what resolution is the vis data held at. i.e. 'at each blitz unit?' or some other arbitraty resolution?
The method I mentioned would give you a list of triangles and surfaces visible from any arbitrary point. It's fast, but not instant. Should be much faster than vanilla blitz linepicks though. Do you have an blitz code example?