Unusual Dark Splodges In Lighting

In a couple of maps I’ve made I’m noticing these weird areas that are much darker than their surroundings with no clear explanation. Here’s a particularly egregious example from pd_c1a2b:

and here it is with mat_fullbright 2:

Removing and re-doing the brush or texture in question or the surrounding brushes doesn’t do anything to change the phenomenon, and copying the brush or moving it to a new location will cause it to not be affected. Changing the lightmap resolution makes the dark spot blurrier or sharper just like any other lighting effect but doesn’t seem to do anything about the underlying dark area:

It’s possible to brighten these areas with a light_spot pointed directly at them, but obviously that means putting a bunch of pointless lights in the map.

Does anybody know what this might be about?

Just a guess. Have you tried disabling shadows?

Could it be some kind of map limit? Have you tried cropping everything away and bake only that part of map?

I’ve tried using cordons, and the anomalies appear regardless of the cordon configuration; however I do think it would be a good idea to copy some of these maps (it only seems to be pd_c1a2a and pd_c1a2b that have the problem) into a new VMF and start deleting stuff until the problem goes away.

I was able to track the effect down to a single brush in the doorframe. There wasn’t anything obviously wrong with it, but either highlighting all of its vertices in Vertex Mode and snapping them to grid (Ctrl-B), or running it through an empty plane-slice transform, seems to have dealt with this particular issue.

However, performing these same operations on the entire map does not seem to have gotten rid of all of the other dark spots visible.

I’m still not sure what is actually causing this, although I figure it has something to do with the fact that these maps came from older versions of the source bsps run through an older version of the decompiler; no stock maps have this problem that I have seen. Being currently unable to tell which brushes demonstrate the issue and lacking an easy solution to ‘heal’ them, globally or one-at-a-time, I guess my best option would be just to start with a new stock decomp and remake pd_c1a2a/b (not as big a concern since most of what I changed was with point entities and those I can just copy over) from scratch, then begin pulling in my expanded geometry room by room.

Well so much for that; a fresh-out-of-the-box modern decompile still shows this issue:

I wonder if it’s worth rolling back Steam versions to when official source maps were a thing to try those?

Maybe selecting everything and Ctrl+B’ing in Vertex Mode will work?

Already tried; no result.

Discovered the problem has to do with curved walls and the ‘smoothing’ system; putting each section of the curve in its own smoothing group causes it to light normally (this can also be done for all walls with the -smooth 0 compiler option).

Pretty sure this is a bug, then, and not an intended part of the engine, but I don’t know if it’s something BM introduced or something pre-existing in Source and so I don’t know where to put the bug report.

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