How accurate are you aiming here? I can help with this, as I know a lot about the PlayStation, along with PSX Doom and what it can and can't handle as far as levels goes.
PSX Doom: The Lost Levels is a community project that will do just that, attempting to make authentic conversions of maps from all of the classic Doom games.
As Gez put it, this is sort of a "Doom the Way Williams Did", and we're aiming for authenticity. Unfortunately, since we can't target the original engine, we can't be 100% certain our conversions would have run on it.
I ask because this can get pretty involved, pretty fast. These levels (sans the normal Doom levels that were omitted from the Jaguar port) were left out of the game for a reason. They are very complex versus the levels that made it in, and some of those featured some pretty extensive changes to their level of detail (especially for levels like Perfect Hatred).
Just making a couple of minor changes to the design of the maps is not going to cut it if you want to be as accurate as possible. These maps are going to need extensive changes to the way they are designed in order even have a chance of them running in PSX Doom.
Here are a couple of basic tips from the original post that I have expanded upon to help start things off.
Limitations on Heights:
PSX Doom has a limit on wall heights. The engine will only vertically tile a texture one time. Because of this, changes in sector height need to be kept to a limit of 256 map units; ceiling and floor heights are exclusive.
So, for example, this room is O.K. (although I'd advise against this for framerate purposes)
This room is NOT:
This is why if you look at some maps in PSX Doom you will see that there are some zero height sectors that surround certain rooms (like the yellow key area in Heck, or the southernmost room in Unto the Cruel). This way the engine is actually rendering two walls that are equal to or less than 256 units in height instead of one that is over. This doubles the polygon count for that wall and has a negative toll on the framerate, so I would advise avoiding it unless it is regulated to one or two small walls or the room is otherwise simple and can not be seen from any other rooms (note how in Unto the Cruel this southernmost room is moved east a bit to get it out of view).
So what would happen if you actually tried to make a room that tall? This (this is simulated, obviously :p):
The engine would just stretch the texture to fit the wall. You can see an example of this in Heck. First, go to the yellow key area, but do not grab the yellow key. Instead, go over to the wall that opens up and releases some monsters into the room when you pick up the yellow key. Whereas the rest of the room uses the 0 height sector trick to get higher walls, this particular place can not, since it is a door. So this texture is stretched to the fit the wall. It's most noticeable if you get up as close as you can to the door and stand near its edge and compare it to the regular wall next to it.
Here is some screens of Heck for those of you who do not have the game:
Let us look at this map shot from E4M8 for a moment:
First off, you should notice the areas circled in blue are highlighting the zero height sectors we talked about in the last section.
For this section, let us concentrate on the stuff circled in red. Notice how most of these are stairs, and how they are simplified in the PSX version. Many times, this is done to lower areas to get rooms under the 256 height limit. However, this is also done because lots of splits in walls and floors will wreck havoc on PSX Doom's framerate (as is primarily the case in E4M8).
Typically, for example, if a staircase was made up of many steps that were 8 units high a piece, it would be made into fewer steps that were 16 units high a piece. If a staircase was already 16 units high a piece in PC Doom, how they approached it varies and it becomes more of a judgment call. If an area was too tall, then they would lower it, thus requiring less steps. Sometimes they would just leave them as is.
Don't be afraid to remove or drastically shrink windows to block view of complex areas.
Sky Exits: (Sky on the ground)
All sky exits were removed in PSX Doom and replaced (usually) with exit teleporters. Reason being is that skies do not tile vertically at all, therefore there is no sky down there to show.
Due to memory constraints PSX Doom typically has less monster variety compared to PC Doom. Considering there are a lot of factors that determine how many monster types you can have in a map (IE how many objects you have, how big the map is, etc) an exact amount is near impossible to determine.
I have, however, made this very basic chart to help you gauge whether you have too many monster types or not. This chart errs towards being somewhat lax.
Demon/Spectre/Nightmare Spectre - 4 points
Imp - 2.5 points
Trooper - 2 points
Sergeant - 2 points
Chaingunner - 3.5 points
Lost Soul - 1 point
Cacodemon - 3 points
Pain Elemental - 3.5 points
Arachnotron - 6 points
Hell Knight - 4 points
Baron of Hell - 4 points
Revenant - 8 points
Mancubus - 6.5 points
Cyberdemon - 12 points
Spiderdemon - 22 points
Total can be used - 26 points
NEW CONTENT ADDED - 12/19/2012
Simplifying 2 sided linedefs:
Moving back to something I forgot to cover in my initial post, let's go back to the E4M8 picture above one more time. This time we'll take a look at the areas circled in magenta; these are places where curves consisting of 2 sided linedefs are simplified. Unless the area is small and well contained, then you should probably do this as well.
Don't bother simplifying one sided linedefs, however, there the benefits in framerate are negligible at best. Only in a few instances in really complex rooms (like E4M2/MAP25 - Perfect Hatred) did the team do this, and even then the benefits were near zero.
I will try to cover some more things (like Arch-Viles, the consolization process, using ChocoRenderLimits for guidance, etc.) when I get some more time.
Last edited by Nuxius on Dec 20 2012 at 01:01