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printz

Dark Forces has "linked portals"?

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Initially I thought it really has 3d maps rendered as 2.5d, but I saw this goof in map 10:


To explain: you're coming through a spiral staircase and this corridor suddenly appears where it shouldn't be.

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From the little I've understood of how the Jedi Engine works, everything that a Doomer would call a "two-sided linedef" is a portal. They're called "adjoins" in the JE lingo. When you draw two sectors sharing a border, the editor automatically creates an adjoin; but you can create other adjoins.

The user-created level known as Perplexion uses this. See some screenshots here

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Gez said:

From the little I've understood of how the Jedi Engine works, everything that a Doomer would call a "two-sided linedef" is a portal. They're called "adjoins" in the JE lingo. When you draw two sectors sharing a border, the editor automatically creates an adjoin; but you can create other adjoins.

That makes it sound very user friendly! Damn. Could this be implemented into a special Doom (or Eternity) map format, to avoid having to remember what specials and tags to use?

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This is a portal *engine*, where the connections between any two primitive divisions of the world geometry define a full-fledged portal, with its own frustum projection and clipping window. This is just like the Build engine, in effect. Eternity doesn't and can't work that way since DOOM requires a BSP-based rendering process.

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If you look at the development blog for the XL-Engine, Lucius talks a lot about getting adjoins to work. The screenshots for OutlawsXL show how the maps use them extensively to create 3D architecture.

http://xlengine.com/

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Gez said:

From the little I've understood of how the Jedi Engine works, everything that a Doomer would call a "two-sided linedef" is a portal.

That's basically how it works. If you look at the automap when crossing these lines, you'll see the section you were in fades out while the section you moved into lights up. Once I found out how that worked, I spent a game keeping track of all the lines that did that.

And yeah I remember that stairway in the picture too. I kept trying to get objects into the lower hallway to see if they'd clash with other objects in the upper hallway.

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Dark Forces seems to only have wall portals, not floor-ceiling ones, explaining the *mostly* lack of over-under bridges. There are however some really simple 3d floors that look conspicuous, such as the thin bridge in level 4 near the start. Most areas separated by portals belong to different layers in the map, but there are a few oddities where you see the floor above or below you in the same layer as yours. Most notably this happens in level 12, by the stairs connecting the docks to the circular corridor. Perhaps this would be easily explained if I had and studied a level editor.

Anyway this wall-portal-only mapping model seems quite practical. I think I'll design my Eternity maps by focusing on wall portals, and using floor-ceiling portals retroactively. They're essentially pits anyway.

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printz said:
Anyway this wall-portal-only mapping model seems quite practical. I think I'll design my Eternity maps by focusing on wall portals, and using floor-ceiling portals retroactively.


Introducing flat portals after basic level geometry is already in place doesn't work that well for myself. At best you're limiting yourself to a pure visual effect, that doesn't add to actual gameplay value.

Better to have a actual "building" structure in mind with different layers, and then come up with ways to connect the various layers. With "building" referring to that section of the map you're working on, not necessarily modelled after a real-life building. I've found this much harder to map for, since you're juggling 2+ layers at the same time, but the result is usually more 'natural' feeling, with gameplay actually making use of the different layers while inside the "building".

...Provided the EE peeps fix / implement the monster / weapon interaction between portals ;)

Mind you, I'm not sure if mine's the right approach. I've looked at the layouts of actual 3D games, like Quake2 and Doom3, sketching the floorplan down on paper. Turns out you can translate lots into plain 2D, with minimal impact on how it plays.

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printz said:

Dark Forces seems to only have wall portals, not floor-ceiling ones, explaining the *mostly* lack of over-under bridges.

Those are called "vertical adjoins" and were added to the Jedi Engine by Outlaws.

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printz said:

There are however some really simple 3d floors that look conspicuous, such as the thin bridge in level 4 near the start.

Sounds like the bridge in the first level of DukeNukem3D, which is done using "flat sprites" (sprites which don't have to face the camera, like mid-masked textures in DOOM but can be flat like floors and ceilings).

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Mordeth said:

Introducing flat portals after basic level geometry is already in place doesn't work that well for myself. At best you're limiting yourself to a pure visual effect, that doesn't add to actual gameplay value.

I think it adds, because any gaps can hinder monster walking, at least.

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