Shooting Through Things: The Video

[Coincident]

This one was 6 months in the making, but it still made it in 2020!

Inspired by Colin Phipps' article "Shooting Trough Things", this is an analysis of doom's flawed collision detection. Learn how the Doom engine makes you shoot through things, even when your aim is perfect.
A special thanks to the folks here who helped review and improve this video, the criticism helped me improve and polish several aspects of the video.
I hope it's clear for everyone.
Any question, ideas, critics, or feedback in general is welcome, just post below.

Enjoy!

 

 

[Starduster]

Really good, high quality video as always. I feel like I'm always learning new things about this game :D.

EDIT: holy crap, congrats on the decino shoutout!

Edited December 30, 2020 by Starduster

[Maximum Matt]

There ya go, a reason to press 'g' on the automap.  

I'm going to blame this on every time I've ever taken damage or died playing Doom :-)

[Pechudin]

This is so well done. I had an intuitive idea for why this was happening, but you really laid it all out for everyone to understand. You are a great teacher!

 

EDIT: So how does ZDooM and onwards fix this bug? Does it also use the corners of the Thing in question or some other way?

Edited December 31, 2020 by Pechudin

[Omniarch]

Excellent video! I've encountered this occurrence more or less every time I've played Doom, and it never even crossed my mind that it might be a bug. How interesting. I am very impressed by the editing, writing and audio quality on display here. Its not easy to find more technical content that is both well-produced and easy for laymen (like myself) to understand.

 

I'm amazed that YT hasn't recommended any of your stuff to me. Your channel is a veritable gold mine of high-quality Doom-related content! What a find!

[Coincident]

3 hours ago, Pechudin said:

EDIT: So how does ZDooM and onwards fix this bug? Does it also use the corners of the Thing in question or some other way?

This is a very good question. I would guess it's the strategy of using the 4-corners (+ the center maybe), but I never saw that code.
Does anyone know?

[Ar_e_en]

If I wanted to actively avoid this issue - should I keep the "128 sized sector" idea in mind when making maps?

[FNSG]

the complexity of what you've presented here almost blew my mind :)...great video btw

[Dimon12321]

@Ar_e_en You mean, while making maps? I don't think that will make much sense. Such issues may pop up while playtesting, and I think it's more reasonable to offset the whole map by some units so a blockmap line along a narrow hallway wouldn't affect the combat anymore.

[Ar_e_en]

10 hours ago, Dimon12321 said:

@Ar_e_en You mean, while making maps? I don't think that will make much sense. Such issues may pop up while playtesting, and I think it's more reasonable to offset the whole map by some units so a blockmap line along a narrow hallway wouldn't affect the combat anymore.

I mean, if the map calls for a narrow hallway - then it's unavoidable, but if I wanted to minimize this occurrence - would I have to pay close attention to the grid lines? 

[Dimon12321]

@Ar_e_en, yes, I think. BTW, I haven't figured how to watch the blockmap in a Doom Builder, so I'm not sure if it's gonna be a comfortable process.