[Can't do] Inherent Doom Mirror Problem

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Inherent Doom Mirror Problem

Postby Rick4574 » Fri Jul 17, 2020 4:52 pm

I've often thought mirrors in Doom had an inherent design problem, but was so because perhaps of software or hardware limitations of the early days in Doom's design.
But, seeing what has been done to Doom these days, with ZDoom, and GZDoom...I wonder if the developers have ever thought about mirrors, what limitations they have, and whether or not these limitations could now be broken or improved on.

Since a line mirror function requires that the sector behind the line to be void, it makes the map maker have to be particularly careful about where to place a mirror in a map, without affecting any other playable area in the map.
The void sector, is in fact a very bothersome aspect of the line mirror function.

Download, and play my Mirror Room example, to see this design flaw I'm talking about. Here's the link:
https://github.com/Rick4574/RS-Doom-Mod ... 20Room.zip

It is an example level, for Doom 2 (map 01).
It was built with Team DRD's Ultimate Doom Builder, and tested with GZDoom 4.5.

In the level, If you go on the roof of the building, and walk to the back of the roof (to about the area where the mirror inside the building was built), you'll see the issue.
I used a Sky texture to somewhat "mask" the issue, where if you where on the ground instead, and looking above the building (near the same area) you wouldn't see the problem.

If the void sector requirement could be eliminated from the Line Mirror function, or perhaps the void sector could instead be located outside the player area of the map (instead of being attached to the line with the Line Mirror function), then that would help the map maker not have to be so particular about where to place a mirror.

Could a line mirror function could be made, where you could have a line tag link it to a remotely located void sector with the same tag?
Kind of like how a line Portal function works?
Or could the Line Mirror function be made, without requiring a void sector attachment?
It was done with floors and ceiling flats (for the reflectivity feature in GZDoom), but not done for a wall line.

I did however, try a mirror with a line portal function also, but it had many other problems than just making a mirror the normal way.

Anyways, I think all the developers of ZDoom, GZDOOM, and Doom Builder are doing a remarkable job!
Keep it going!!!
Thanks.
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Re: Inherent Doom Mirror Problem

Postby Graf Zahl » Fri Jul 17, 2020 5:45 pm

The hardware renderer displays this properly because it has options to mask out the unwanted parts. The software renderer cannot do that, and this is where the limitation comes from.
If you want software rendering support you have to play by strict rules that cannot 'just' be removed.
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Re: Inherent Doom Mirror Problem

Postby Henry Hamblewill » Fri Jul 17, 2020 7:16 pm

Thanks Graf,
Although, I don't really understand your replay.
I guess it's because I don't really know the inner coding of the Doom engine...I'm just a good map maker really.

Are you saying it can't be done? After all the awesome tricks you guys have done already?
It would just break my heart if you guys couldn't do it. :(

You guys gonna even try on this?
I bet you guys could come up with a good trick If you give it a little effort! I bet you guys could fix it!
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Re: Inherent Doom Mirror Problem

Postby Caligari87 » Sat Jul 18, 2020 7:51 am

Yes, Graf knows the inner workings of the Doom engine.

If this could be easily changed, it would have been changed fifteen years ago.

8-)
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Re: Inherent Doom Mirror Problem

Postby Apeirogon » Sat Jul 18, 2020 9:57 am

...cough...sound slots...cough...
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Re: Inherent Doom Mirror Problem

Postby Graf Zahl » Sat Jul 18, 2020 10:00 am

You clearly have no idea what you are talking about. The issue with the sound slots was merely an API issue not a technical one, but this is a fundamental limitation of how the software renderer composes a scene.
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Re: Inherent Doom Mirror Problem

Postby Apeirogon » Sat Jul 18, 2020 10:19 am

Oh wait, software!?
Then yes, my bad.
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