How large can a UDMF map be?

[gemini09]

Hi

I'd like to ask if the UDMF format allows for a map to be as large as the "drawing space" in the GZDoomBuilder editor.

In GZDoomBuilder, the real estate offered for you to make your map in, is 64,000*64,000 units.

However, I know from experience that "Doom in Hexen format" could not cope with really large maps - collision detection, possibly a result of nodes unable to build and maintain over that large distances, was the problem where the player could walk through walls and enemies could not be harmed as bullets also "walked through" [the enemies].

I hope UDMF has improved on this, as this is something really constraining to me - I enjoy gigantic landscapes, as they allow for trekking back and forth between for instance UAC bases scattered on a moon, and it's unorthodox for Doom, which has its appeal as we continue to make maps 20 years later and it's time for something fresh and new.

[Graf Zahl]

The general rule is that two points in a map may not be more than 32767 map units apart. That's not a map format limitation but a result of the fixed point numbers the Doom engine uses. ZDoom as the only current port with UDMF support has not yet removed this particular limit.

[gemini09]

My last experience with this was in 2009, and it seems there has been zero focus on this issue. What do you think the future holds? Personally I would love to have it right away, and I'm sure others would as well, as it would encourage a different kind of level design which would be very interesting for our community maps. But there could be an enormous technical obstacle in the way that may not be feasible to overcome, that I'm not aware of.

[printz]

Graf Zahl said:

The general rule is that two points in a map may not be more than 32767 map units apart. That's not a map format limitation but a result of the fixed point numbers the Doom engine uses. ZDoom as the only current port with UDMF support has not yet removed this particular limit.

Would it work if the fixed points are formatted in 48:16 64-bit values? Sure that large span wouldn't be needed for most levels; just for big map experiments (which would suck because they would just emphasize Doomguy's exagerrated speed).

[Blue Shadow]

I guess you can use hubs for the time being to divide the map into smaller chunks.

It has its limitations, of course, but I think that's the next best thing...

[Quasar]

Unless every single intermediate math op in ZDoom is resistant to integer overflow when calculating distances, you may find the real limit to be significantly less than 32767. That may be the case, of course. It's just that doing math on integers can reduce the point of overflow to as little as 8192 units depending on the type of operation being done (multiplications are bad in particular).

[Gez]

Some variables had to be promoted to 64 bit before calculations to get rid of bugs in traces in gigantic maps like Memorial.

[Kappes Buur]

Hopefully nobody will make a map larger than about 15000 x 15000, for sake of insuring
a somewhat smooth gameplay.

The map I am working on at the moment is ca. 22000 x 25000, running at slightly over 14 fps.
And that is on a fairly good computer. Needless to say that it will never be published as is.
I am seriously considering to rework it into hubs.

[gemini09]

First off, I personally find value in almost endless landscapes and I strongly disagree with the notions that it's inappropriate for Doom. If anything, the traveling speed would only complement large distances, further elevating the exploration and free-form game style that Doom possesses. I must also admit I'm a little offended by the two baseless discouragements here...

Secondly, Quasar and Gez posts seem to have omitted their contexts, or something... I didn't aqcuire any new insight from it, at least.

[clamgor]

Never knew there were limits as to how big maps could be and that people want to make such big maps.

But I guess since the Doom engine was limited anyway, knowing that there's a limit for how big maps can be should've been common knowledge.

[gemini09]

I'm sorry; what was your point..?

[clamgor]

gemini09 said:

I'm sorry; what was your point..?

Oh sorry, I wasn't answering your question, I was pondering about Doom having limits with map creation.

I never really thought of it 'till you brought up the fact that there are limits.

[gemini09]

I find that the "Line horizon" action #9 (in UDMF) encourages one to map far into the horizon, at least once you have a decent landscape floor texture and a complementing sky. Besides that, I'm just fond of enormous landscapes, where you can include paths to other bases and whatnot - interconnected in a larger scale, in other words, where the trek between them can be a journey in themselves, and I see a lot of potential in it. Not to mention that landscapes are very appealing in Doom because of how simple and economic the engine is.

Anyway; thanks for your inputs, Graf Zahl, Blue Shadow, and everybody.