Ghost/Phantom Lines: Map Cracks

Hey folks, got a simple one for the pros here. I have spent some time searching for a solution to what I call Phantom Lines that bleed through into the map. Due to the lack of correct terminology in defining what these are, could prove as to why I was unable to find an adequate solution to this problem. I have on multiple occasions just deleted sectors and started over, but if there is a more practical approach I'd prefer it. Thank you for your help in this matter.

^^^Bottom of door, left of shotty.



Underneath Cacocorpse, right of shotty^^^

Those look like Slime trails to me. Hard to tell though.

Mechadon said:

Those look like Slime trails to me. Hard to tell though.

Thanks for the help. That was what I was looking for!
For the sake of clarification, (to see if I actually understand this) but this is a combination of my noobism in map building and having lines that are positioned where the game engine mathematically cannot define it correctly?

Not so much noobism as slime trails happen to every body who draws maps with a floor plan more developed than a Wolf 3D level. (And even then, I'm sure it's possible to have slime trails with orthogonal, gridsnap-128 maps too.)

The real problem is that in the normal node format, additional nodes can be placed by the nodebuilder at decimal positions but it can only write integral coordinates. So there is a precision loss which results in slime trails.

If you're mapping for ZDoom, PrBoom+ or Eternity, you can use extended nodes which will give greater precision (since nodes are written with decimal coordinates) and eliminate or at least very strongly reduce such things.

It's probably not a result of your 'noobism', unless you've managed to screw up something that I've never even heard of before. It's just something that you have to live with in Doom, to an extent. If I encounter the problem in an area where it's really noticable, it often helps to move the nearest vertice around by a few units and rebuild the BSP, but not always. I'm not sure what nodebuilder you're using, but as long as it's fairly recent it's probably already designed to avoid splitting segs in places that risk slimetrails.

IIRC, ZDBSP's extended nodes can reduce the likelihood of slime trails, but only a handful of ports will support the format, so it's not always ideal.

[Edit: Damnit, I stepped away for a drink of water, and Gez replied in the interrim. :P Interestingly, 'map crack' is the most evocative name I've ever heard for the phenomenon.]

I just figure the noobism comes into play if there are excessive amounts of "Slime" due to a bunch of wacky angles. Then in this case excessive would need to be defined! Any how, I have tested the map in ZDOOM and didn't even notice any slime as of yet. I hope to release the map today or tomorrow. I still have a few questions and some FAQ's to read before submission. And yes, I have the TEXT file. :P