Not VPO! Not Medusa! Kills Chocolate and Crispy! Most excitingly mysterious texture-related error EVER.

[RaphaelMode]

• Download this file.
• Play the first map in something vanilla-esque. Play it with -nomonsters, -skill 0, or just IDDQD+IDKFA, it makes no difference.
• Enter the bigger tunnel on the right, turn right, go out on the large courtyard and cast your gaze, once again, to the right.
• BEHOLD! At some point, the game crashes.

 

And one more amazing thing is, removing the custom textures OR removing all things from the map and moving the player start closer to the anomaly FIXES the crash! I would have debugged this further, but I'm already filled to the brim with wonder at the mysteriousness of the universe and will absolutely, definitely NOT handle any more of it today. There are various other potential fixes I haven't tested yet, such as disconnecting the wifi, moving my computer to a different room, or launching Chocolate Doom with my eyes closed. Good luck to anyone willing to take a look at this.

ZZERROR2.zip

[scifista42]

13 hours ago, Altazimuth said:

You've got a multipatch on a 2S midtexture somewhere,

 

That was my first thought too. However, I've found out that the crash actually happens when looking at line 328, which is a 2-sided line that has SW1SKULL as a midtexture. Removing the texture fixes the crash. The mystery is: This texture is not multipatch.

 

13 hours ago, Altazimuth said:

Edit: I think it's line 2562, at least?

 

Line 2562 is 2-sided with a multipatch midtexture, but the texture's patches don't vertically overlap, which they would have to in order to trigger the crash. Looking at the line indeed doesn't crash the game.

Edited September 15, 2018 by scifista42

[Altazimuth]

It's a Medusa. I've debugged it and it crashes exactly where a Medusa does, doing a read access violation in R_DrawMaskedColumn. Choco crashes even on mostly symptomless Medusa errors, that vanilla handles just fine. You've got a multipatch on a 2S midtexture somewhere, and it needs to be fixed. (Thanks to Quasar for actually telling me what my findings mean; he's the one that actually knew this stuff.)

 

Edit: I think it's line 2562, at least?

Edited September 15, 2018 by Altazimuth

[RaphaelMode]

I have figured it out! To make things extra fun, the midtexture was on the edge of a 0-height sector, so it was impossible to see during gameplay or in the 3d view.

 

I originally had the SW1SKULL texture be a 128-wide texture with one 128-wide patch, but then I changed my mind and replaced the patch with an 8-wide one to be used for something else. I planned to update the SW1SKULL later, thinking I haven't used it for anything before. But apparently, it was used there.

 

So here's the last fun fact: A medusa effect doesn't just show up when there's more than one patch per column. It also shows up when there's less than one patch per column! It's still possible to make textures with seemingly empty columns, by using patches offset lower than the texture's height. Then they're invisible, but they still prevent the medusa!

 

How did you debug Chocolate Doom to get that information? Maybe I would've gotten further on my own if it wasn't just shutting down without any feedback.

[scifista42]

26 minutes ago, RaphaelMode said:

How did you debug Chocolate Doom to get that information?

 

I knew from previous experience (multiple past DW threads, and I don't think it was me who made the initial discovery) that a crash with no feedback happens when the player looks at a 2-sided line that has a multipatch midtexture with vertically overlapping patches. So I opened your map in Doom Builder and looked at lines in the area you described and checked whether their midtextures are multipatch in SLADE3. I didn't find any multipatch midtextures, but the SW1SKULL seemed suspicious to me anyway (redefined switch, empty columns). Then I finally launched Chocolate Doom and quickly confirmed that the crash happens exactly when that one line comes into the player's view. Then I removed the texture and tested again and it didn't crash.

[fabian]

If this is medusa issue, then Crispy Doom should *not* be affected by this!

[fabian]

On 9/15/2018 at 10:31 PM, RaphaelMode said:

So here's the last fun fact: A medusa effect doesn't just show up when there's more than one patch per column. It also shows up when there's less than one patch per column! It's still possible to make textures with seemingly empty columns, by using patches offset lower than the texture's height. Then they're invisible, but they still prevent the medusa!

 

And now this is also fixed in Crispy Doom, thanks!