@dysfun I was in a 737 taking off, and the captain came on and said "folks we have a warning light on in the cabin. It's probably nothing, but regulations say we have to land again and get it cleared. Sorry for the delay."
Landed the plane again, and once on the ground he said "hey folks sorry for that little fib earlier. What actually happened is we lost the port engine. But I didn't want to worry you until we were on the ground. We'll be transferring you to another plane soon."
Tom Forsyth
@TomF@mastodon.gamedev.place
mastodon
4.5.9
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Apr 13, 2026
31
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Apr 11, 2026
@0xabad1dea it turns out Myst is unbeatable. For him.
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0
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Apr 09, 2026
@lritter I have cats for that.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Apr 09, 2026
5
0
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Apr 09, 2026
@ZachWeinersmith Small niggle - it wasn't clear that the narrator was a specific person (Mr. Tao) rather than an abstract character. I only realised at the end and had to go back to find their name.
3
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Apr 07, 2026
Loads of other competitions - limited-space ones, live-coded ones, graphics-only, sound-only, etc - on their YT channel - go check it out.
A category I am personally fond of - the fantasy consoles! A great way to experience the limits (and low expectations!) of old machines without quite so much frustration.
https://www.youtube.com/watch?v=49YjC8dWdqE
A category I am personally fond of - the fantasy consoles! A great way to experience the limits (and low expectations!) of old machines without quite so much frustration.
https://www.youtube.com/watch?v=49YjC8dWdqE
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Apr 07, 2026
Amiga demos. Same thing - don't be afraid to fast forward, but make sure you watch the last few.
https://www.youtube.com/watch?v=KFVxntafsXM
https://www.youtube.com/watch?v=KFVxntafsXM
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Apr 07, 2026
Revision 2026 PC demos.
It's long, but don't be afraid to use that fast-forward button, and remember they're sorted roughly by quality, so make sure you at least watch the last few!
https://www.youtube.com/watch?v=Lw4W9V57SKs
It's long, but don't be afraid to use that fast-forward button, and remember they're sorted roughly by quality, so make sure you at least watch the last few!
https://www.youtube.com/watch?v=Lw4W9V57SKs
20
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Apr 06, 2026
@jplebreton This is particularly distressing to me. I rather liked both of them, personally. I guess people change.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Apr 04, 2026
This weekend, Subnautica is free to play, and it and the full-sized sequel Below Zero are both 75% off to buy. If you have not tried these you absolutely should - I recently replayed them both and they're still so good.
https://store.steampowered.com/app/264710/Subnautica/
https://store.steampowered.com/app/264710/Subnautica/
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Apr 01, 2026
7
0
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Apr 01, 2026
@rygorous Not sure how you forgot to mention the gold gold gold gold, gold gold gold gold.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Mar 31, 2026
@wolf480pl @rygorous I don't know how many used SGI hardware. There were still a fair number of dedicated military graphics systems from various companies, some of whom later moved into the consumer space, e.g. Martin Marietta. I used to know more about this space because 3Dlabs bought a ton of their patents, and one of my jobs was spotting which other companies were violating "our" patents. But time has not been kind to my memory.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Mar 30, 2026
@rygorous I am curious about the use of indexed colour on this machine. Surely it had enough memory and bandwidth to use (at least) 24bpp true-colour for the UI?
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Mar 30, 2026
@rygorous "In February 1995, SGI reduced the entry price of Reality Station to US$179,540"
"Reduced" and "entry price" are doing a lot of heavy lifting here.
At the time, a brand new Ferrari F355 cost $128k.
"Reduced" and "entry price" are doing a lot of heavy lifting here.
At the time, a brand new Ferrari F355 cost $128k.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Mar 30, 2026
@rygorous Interesting:
"true HDTV (1920 x 1035) resolution"
I wonder where that specific rez came from. The 1.85 ratio seems common in cinema, but then they combined it with 1920 wide.
"true HDTV (1920 x 1035) resolution"
I wonder where that specific rez came from. The 1.85 ratio seems common in cinema, but then they combined it with 1920 wide.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Mar 30, 2026
@rygorous As we know, caches are a giant pain in the arse to design and build. So... they didn't!
5
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0
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Mar 08, 2026
@justdaveisfine This is a completely real story BTW.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Feb 28, 2026
@nash
Sega Japan: we have a new character. He's a fox. Very fast. His name is Miles Prower.
Sega US: he has two tails - that's cool. Let's call him Tails.
Sega Japan: yes, he can fly very fast with them. His name is... Miles Prower!
Sega US: eh, too long. We prefer Tails.
Sega Japan: Miles. Prower. Geddit? It's a pun. In English. Please. We spent so long workshopping it for the US market. So many translators.
Sega US: these crazy Japanese, what are they on about. "Tails" it is!
Sega Japan: we have a new character. He's a fox. Very fast. His name is Miles Prower.
Sega US: he has two tails - that's cool. Let's call him Tails.
Sega Japan: yes, he can fly very fast with them. His name is... Miles Prower!
Sega US: eh, too long. We prefer Tails.
Sega Japan: Miles. Prower. Geddit? It's a pun. In English. Please. We spent so long workshopping it for the US market. So many translators.
Sega US: these crazy Japanese, what are they on about. "Tails" it is!
0
0
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Feb 15, 2026
@gsuberland @artemist @ryanc So the first part is not correct - k0 does NOT return all-1s.
But it is correct that "kxnorw k1, k0, k0 sets k1 to all ones"! Because so does "kxnorw k1, k5, k5"
But it is correct that "kxnorw k1, k0, k0 sets k1 to all ones"! Because so does "kxnorw k1, k5, k5"
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Feb 15, 2026
@gsuberland @artemist @ryanc Morbid interest I wondered if Google's AI got this rather esoteric question right. It actually did! Almost. It fell over right at the end on this, which is amusingly "not-even-wrong":
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Feb 15, 2026
@gsuberland @artemist @ryanc "Designer" has a very specific meaning in Intel jargon - those are the people doing low-level layout & timing.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Feb 15, 2026
@gsuberland @artemist @ryanc It was very annoying to have to invent a whole new register file and mini-ISA, but the designers would have chased me with flaming torches and pitchforks if I'd tried to make them do it with GPRs.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Feb 15, 2026
@gsuberland @artemist @ryanc It would have been elegant architecture to use the GPRs, but physically it would have been a bad idea - the two live in very different parts of the chip. I talk about it in my video:
https://vimeo.com/450406346
k0 is a perfectly normal register. The only special thing is that for vector instructions, that ENCODING is used to mean "no mask". This is similar to how SP/BP/R12/R13 encodings meaning special things in MOD-R/M - the registers themselves aren't special.
https://vimeo.com/450406346
k0 is a perfectly normal register. The only special thing is that for vector instructions, that ENCODING is used to mean "no mask". This is similar to how SP/BP/R12/R13 encodings meaning special things in MOD-R/M - the registers themselves aren't special.
1
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Feb 15, 2026
@kenshirriff That is a honking big register stack. I keep forgetting it's 80 bits per reg!
1
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Feb 15, 2026
@artemist @gsuberland @ryanc I can personally assure you that k0 is a very real and existing register.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Feb 15, 2026
@TimWardCam @ryanc IIRC, the ZX Spectrum relied on the R register for correct screen display? I'd need to recheck the book.
1
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Jan 24, 2026
@juanfr It was strange to have the game be significantly better than the film. Not the usual way.
1
0
0
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Jan 24, 2026
@juanfr Fun fact - that "iconic" gun was spectacularly weird and bad:
https://www.youtube.com/watch?v=xEeEfsY_RBw
https://www.youtube.com/watch?v=xEeEfsY_RBw
0
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 28, 2025
@Nucu No idea, sorry. HL:A was after my time.
My guess is they tried it and it just didn't feel satisfying? I've not seen a melee combat system that worked that well. Doesn't stop people trying (nor should they!). Beat Saber is deliberately NOT that - it's laser beams through jelly cubes :-)
My guess is they tried it and it just didn't feel satisfying? I've not seen a melee combat system that worked that well. Doesn't stop people trying (nor should they!). Beat Saber is deliberately NOT that - it's laser beams through jelly cubes :-)
1
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 28, 2025
2
0
0
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 27, 2025
@Felice @Farbs DK2 was already so much better than DK1. It had positional tracking, 90Hz, low-persistence, far better contrast, and we had done Real Optics rather than dialling in a bunch of magic polynomials by eye. We really knew we'd cracked it then - everything after was fairly small increments.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 24, 2025
@Felice @Farbs Nah, we did pretty good latency mitigation. The problem was no positional tracking - rotational only. You'd be surprised how important that was - even the centimeter or so of parallax as you rotate your head is really important. I spent a while trying to refine our "neck model" but by then we had the DK2 tracking almost figured out.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 24, 2025
@Farbs It is how we learned it, too! We put about 30 Valve people through a battery of questions before and after playing TF2 in DK1 for a fixed amount of time. I did all the interviews, and by the end of the week I asked about "nausea" so many times I'd given myself a Pavlovian response to the word that stayed with me for about 5 years afterwards.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 21, 2025
But on the SSE version, a whole bunch of tiny precisions are very slightly different, and a combination of the friction on the floor and the mass of the objects means the guard still rotates from the collision, but now he rotates very slightly less far.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 21, 2025
On both versions, the door has just enough momentum to rotate the guard very slightly. The guard's friction on the floor is not quite enough to oppose this, and he rotates a tiny fraction of a degree. On the x87 version, this tiny rotation is enough to move his toe out of the way, the collision is resolved, and the door continues to swing open. All is well.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 21, 2025
This collision is actually properly modelled - a big innovation of HL2 was the extensive use of a real physics engine. The door and the guard are both physical objects, both have momentum, they impart an impulse on each other, and although the door hinge is frictionless, the guard's boots have some amount of friction with the floor.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 21, 2025
So problem solved, right? 80 bits of precision means the collision didn't happen, but in 32 bits of precision it does, and that's your problem, more bits better, QED, right? Well not quite.
The guard's toe overlaps in both cases - a few millimeters is still significantly larger than ANY of the possible precisions. In both the SSE and x87 versions, the door hits the guard's toe. So far, both agree.
The guard's toe overlaps in both cases - a few millimeters is still significantly larger than ANY of the possible precisions. In both the SSE and x87 versions, the door hits the guard's toe. So far, both agree.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 21, 2025
But ten years later in 2013, SSE had been standard in all x86 CPUs for a while - the OS depended on it being there, so you could rely on it. So of course by default the compilers use it - in fact you have to go out of your way to make them emit the old (slightly slower) x87 code. SSE uses a much more well-defined precision of either 32 or 64 bit according to what the code asks for - it's much more predictable.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 21, 2025
So this kicked off an even longer bug-hunt. The answer was (as with so many of my stories) good old floating point. Half Life 2 was originally shipped in 2004, and although the SSE instruction set existed, it wasn't yet ubiquitous, so most of HL2 was compiled to use the older 8087 or x87 maths instruction set. That has a wacky grab-bag of precisions - some things are 32-bit, some are 64-bit, some are 80-bit, and exactly which precision you get in which bits of code is somewhat arcane.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 21, 2025
OK cool now we can ship the game phew. But why did this EVER work? The guard's toe was in the way in the original version as well. As I say, we went back in time and compiled the original as-shipped source code - and the bug happened there as well. It's always been there. Why didn't the door slam closed again? How did this ever ship in the first place?
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 21, 2025
Once we'd figured this out, the fix was simple - move the guard back about a millimeter. Easy. But it took a lot of work to find because people had to dust off old memories of how the debugging tools worked, etc.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 21, 2025
If you watch the video, when the door unlocks and then opens, there's a second guard standing inside the room to the left of the opening door. That guard is actually standing very slightly too close - the very corner of his bounding box intersects the door's path as it opens. So what's happening is the door starts to open, slightly nudges into the guard's toe, bounces back, closes, and then automatically locks. And because there's no script to deal with this and re-open the door, you're stuck.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 21, 2025
After about a day remembering how to use the debugging and replay tools, someone smart (sorry, I don't remember who) figured out what was going wrong.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 21, 2025
Someone even goes back in the source history and compiles the original game as it shipped - nope, that original version is also broken. How can this possibly be? At this point people are freaking out - this isn't a normal bug - it appears to have traveled backwards in time and infected the original!
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 21, 2025
Oh dear. We can't ship this. I get some other folks, including some folks who worked on HL2 originally, and yep - it's broken. And it's broken when you're not in VR either - so it's not something Joe and I broke. But nobody knows why - none of the relevant code has changed.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 21, 2025
I checked a video online, wondering if my memory was faulty - nope, the door's meant to open automatically, and you walk in. https://www.youtube.com/watch?v=y_3vMUOayyc&t=215s (at 3:40). But... now it doesn't!
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 21, 2025
What is meant to happen is a guard (spoiler alert - it's actually Barney in disguise) bangs on a door, the door opens, he says "get in", and then the game waits for you to enter the room before the script proceeds.
But in this case the door sort of rattled, but didn't open, and then locked shut again. So you can't get in the room, and the gate closed behind you, so you can't go do anything else. The guard waits forever, pointing at the locked door, and you're stuck.
But in this case the door sort of rattled, but didn't open, and then locked shut again. So you can't get in the room, and the gate closed behind you, so you can't go do anything else. The guard waits forever, pointing at the locked door, and you're stuck.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 21, 2025
So I started it up, selected new game, played the intro section. It's a fairly well-known section - you arrive at the train station with a message from Breen, a guard makes you pick up a can, and then you have to go into a room and... uh... I got stuck. I wasn't dead, I just couldn't go anywhere. I was stuck in a corridor with a guard, and nowhere to go. Bizarre.
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Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
Tom Forsyth
@TomF@mastodon.gamedev.place
Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.
mastodon.gamedev.place
@TomF@mastodon.gamedev.place
·
Nov 21, 2025
Of course we've played a bunch of HL2 by this point, testing all the VR stuff works. But we just skipped to the relevant chapters - we never actually played through from the start. And I hadn't played it through in a while, so I thought I'd do that in VR, start to finish. If I discovered anything that still didn't work, I could at least document it in the release notes.
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