Slime Trails and Mirrors

[Charybdizs]

In the map I'm working on for the OLDC, I somehow managed to get a small slime trail and multiple hall of mirrors. I've checked multiple times, there is definitely no textures missing... Can anyone give me some ways to get rid of them? I'd prefer not to have to show the map, but if I do, I could PM it to anyone that wants to help I guess...

 

[Fawfulfan]

I've had to deal with this all the time in Tortured Planet. Even now, you can still see a couple of slime trails in scattered places (the most severe ones being in the underground lake room in Sunshine Atoll Zone Act 2 and the very first asteroid field of Spacewalk Zone Act 2). For every slime trail you see in my levels, maybe ten or twenty more were painstakingly wrestled out of existence before I threw up my hands and decided that a particular one was the least bothersome.

The core cause of this problem is that the nodebuilder doesn't always build structures exactly as they are in SRB2DB. Sometimes they have to round off on distances, which tends to create openings and leaks in sectors that cause slime trails and HOMs. This problem seems to be further exacerbated by copious conjunctions of "invisible Thok Barriers" (Thok Barriers with F_SKY1 as both their floor and ceiling) with regular Thok Barriers. Ultimately, it all boils down to one or two vertices that were put in unfortunate places in your map. That's a bigger problem than it sounds; it's pretty much impossible to predict what configuration will cause problems until you've built it and tested it.

I have a pretty ironclad 5-step method for trying to get rid of slime trails:

1. Determine the direction the slime trail is coming from (in other words, which way you have to look to see it.)
2. Look at your map and work out a "slime trail vector" based on what direction that corresponds to.
3. Regard any vertices close to the vector as suspect.
4. Play around with those vertices. Move them in different directions, attach new sectors to them, remove existing sectors, etc., each time testing the level again to see whether any of the modifications shrinks or eliminates the slime trail. There are all kinds of things you can typically try, so test every possibility you can think of.
5. Eventually, one of the things you try will either make the slime trail vanish or become less severe. If it is entirely gone, well, pat yourself on the back. If it's just a little smaller, then take what you did before and make it more pronounced (that is, if you moved a vertex 32 fracunits up last time, move it up another 32 fracunits and see what that does). Repeat as necessary.

It's a fair amount of work, but it is pretty much the best method I know of. I hope that helps!

 

[MascaraSnake]

I suggest trying ZDBSP. I've heard it's actually become better than ZenNode in recent time. Dunno if that's try, but I say you should try it out and see if it eliminates one or another slime trail.

 

[SSNTails]

'Check for unclosed sectors'.

 

[Charybdizs]

I was able to fix it just by adding another vertice right next to it. Thanks for the advice. I still have some halls of mirrors though...

 

[Fawfulfan]

'Check for unclosed sectors'.

How do you do that?

 

[Kyasarin]

How do you do that?

If you're using SRB2 Doom Builder (I don't see why not), just press F4 and check the "Unclosed Sectors" box.

 

[MascaraSnake]

How do you do that?

Wait, you seriously didn't know that you can look for unclosed sectors, or that unclosed sectors cause slime trails and HOMs?

 

[Fawfulfan]

No, of course I knew that. If I didn't know that, how the heck do you think I could have given such a coherent explanation of the problem at the beginning of the thread? I just thought that he meant there was some kind of extra utility that can spot errors in the BSP build.

BTW, I tried using ZDBSP, and it doesn't seem to work with SRB2 Doom Builder. I got an error.

 

[MascaraSnake]

BTW, I tried using ZDBSP, and it doesn't seem to work with SRB2 Doom Builder. I got an error.

Did you look at this?

 

[Fawfulfan]

Oh, wow.

I got it up and running, and it's pretty impressive. ZenNode would take maybe two minutes to build nodes for SWZ2; ZDBSP can do it in three seconds! I've heard good things about its PolyObject-rendering abilities, too, but I haven't tested those yet.

I will give anyone using ZDBSP a few words of caution, though. First of all, it seems to be terrible at compression. Build nodes with it and any WAD will get bigger. Second, the slime trails it produces aren't less severe, just different. Switching to ZDBSP will produce as many slime trails as it gets rid of.

 

[Shadow Hog]

I've heard good things about its PolyObject-rendering abilities, too, but I haven't tested those yet.

Only relevant to ZDoom and Hexen-style polyobjects, I thought. I doubt it has any bearing on SRB2's, considering we don't use the Hexen map format.

 

[Spongecar]

I will give anyone using ZDBSP a few words of caution, though. First of all, it seems to be terrible at compression. Build nodes with it and any WAD will get bigger. Second, the slime trails it produces aren't less severe, just different. Switching to ZDBSP will produce as many slime trails as it gets rid of.

I'm a week late. Oh well. About ZDBSP creating slime trails. Use that for play tests then build the final map in Zennode?

 

[JakeDimick6192]

I know how to make so you can't have hall of mirrors, or slime trails! Slime trails happen when you make a trigger sector, or whatever it's called, and drag it inside the sector. keep it outside the thok barrier. Hall of Mirrors happen when you don't make a thok barrier or you don't fill in the missing textures. make a thok barrier, or fill in any missing textures. i had problems before with thok barriers before, now i'm good. i used a sector height of 128 for my levels. also, i had problems with missing textures before, now i use 3d mode to fill them. hope you do better at it!

 

[Fawfulfan]

I know how to make so you can't have hall of mirrors, or slime trails! Slime trails happen when you make a trigger sector, or whatever it's called, and drag it inside the sector. keep it outside the thok barrier. Hall of Mirrors happen when you don't make a thok barrier or you don't fill in the missing textures. make a thok barrier, or fill in any missing textures. i had problems before with thok barriers before, now i'm good. i used a sector height of 128 for my levels. also, i had problems with missing textures before, now i use 3d mode to fill them. hope you do better at it!

Those are all incredibly simple, beginner's mistakes that everyone already understands. Some slime trails also happen as a result of suboptimal vertex placement, which is much harder to solve. That's what we're talking about here.

 

[SSNTails]

Only relevant to ZDoom and Hexen-style polyobjects, I thought. I doubt it has any bearing on SRB2's, considering we don't use the Hexen map format.

No, it applies, however ZDBSP does not look for the SRB2 polyobject linedefs - only the Hexen ones, so the feature is never activated.

I believe the way current SRB2 polyobjects are built (including in the tutorial), work around the regular limitation to make ZDBSP's feature irrelevant, anyway. (All you have to do is surround the polyobject control sector with a square sector, which we do already.)

 

[Charybdizs]

Well, I've hardly even responded to this thread of mine, I just wanna pop in to say that this advice fixed all my map errors!