r505 Black diagonal artefact

[Enjay]

I thought I'd seen something like this reported before but I can't find it ATM so, just in case, here it is.

This big black artifact shows in map02 of the file available from this thread:

http://www.doomworld.com/vb/wads-mods/4 ... -in-1-wad/



If I switch off dynamic lights or force additive lighting, the artefact vanishes.

[Graf Zahl]

Hm. For whatever reason, when sorting the segs belonging to a sidedef I skipped sidedef 0...

Fixed.