Sprite clipping issue, GZDoom

[Andy Johnsen]

I figured I would resume work on some GZDoom based map I put some time into a few years back. At the time I was using an older build of GZDoom since I had trouble getting the more up to date ones to run on my system (ended up getting g1.8.09-78-g1db064b to work, so I went with that for the time being).

Now, installing the latest 2.2.0 build seems to give issues with lots of sprite clipping / flickering and various other issues. I used some unconventional sizes for the given tree sprites. Runs with no issues on the old GZDoom build however, but with the new one even slight sprite overlapping causes flickering and odd clipping. Anything specific that could cause this? (I'm using a NVIDIA GeForce GTX 1060, and as mentioned, the old version runs identical on this system as it did on my old one. Tried tinkering with the settings, but it seems futile).

[Gez]

Could you post some screenshots? From your descriptions it seems more like Z-fighting, by having several sprites at the same place.

[Andy Johnsen]

You're probably right. The problem only occurs with certain sprites that will overlap slightly and bleed through each other as you move by.

The shot below illustrates a sprite placed on a sector in the back, bleeding through the tree sprite on a ledge below. Moving by, you'll get the flicker effect, and when you have plenty of these it looks unacceptably ugly.

I do wonder why it worked just fine in the old build however

[kb1]

The trees are sprites, right? Move the small tree (the one that's incorrectly peeking through) back a bit, and/or move the big tree forward a bit.

The engine has to sort the sprites based on the distance from the player. It uses the sprite's X and Y coordinates vs. the player's X/Y to calculate distance. But most engines cheat a bit with this calculation for speed, so it's not always accurate. And, you have to consider that your viewing essentially cardboard cutouts for trees, cause sprites are basically 2D billboards with no thickness.

Move them away from each other a bit, and they should render fine (unless some recent change broke this - you mentioned that the behavior recently changed. I don't know about that.) Good luck - your screenshot looks interesting :)

[Andy Johnsen]

kb1 said:

The trees are sprites, right? Move the small tree (the one that's incorrectly peeking through) back a bit, and/or move the big tree forward a bit.

The engine has to sort the sprites based on the distance from the player. It uses the sprite's X and Y coordinates vs. the player's X/Y to calculate distance. But most engines cheat a bit with this calculation for speed, so it's not always accurate. And, you have to consider that your viewing essentially cardboard cutouts for trees, cause sprites are basically 2D billboards with no thickness.

Move them away from each other a bit, and they should render fine (unless some recent change broke this - you mentioned that the behavior recently changed. I don't know about that.) Good luck - your screenshot looks interesting :)

Thank you for the input :)

Yeah, moving them would indeed fix the issue, I'm mainly wondering why it became an issue from one version of GZdoom to another, given the old build handles this fine, you do get sprites passing through each other, but it doesn't blank out the sprite in front of it in the process, like in the recent version. In the old one it just simply seamlessly clips through. The picture does not capture the flickering effect, it just showcase a sprite placement where such occurs because of the proximity.

It would require many hours of rework to fix every overlapping sprite placement issue in the map (it's an enormous thing) and many areas have been designed / composed specifically for a certain density and combination of sprites, so if there's a possible setting to combat this I'd want to try that first. :)

[Graf Zahl]

Get a more recent devbuild, that problem had been fixed several weeks ago when I noticed it myself.

[Andy Johnsen]

Graf Zahl said:

Get a more recent devbuild, that problem had been fixed several weeks ago when I noticed it myself.

Fantastic! That's what I get for not realizing there's a more up to date version. Thanks :)