Tom Forsyth

Graphics coder and HW architect, previously at Muckyfoot, RAD Game Tools, Valve, Oculus, Intel, Rec Room and Riot.

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Last Notes

2026-05-04 05:04:37 UTC

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Incidentally this means the smallest distance is 233 nanometers, which should be sufficient for most gaming purposes?

2026-05-04 04:59:17 UTC

Writing a fixed-point position class, and Neptune is 4.4 billion km away. So a reasonable scale for the upper 32bits would be (1<<32)km. But converting to meters that's (1<<32)*1000, which is not an exact float32. How about I use (1<<32)*1024 instead? So not kilometers, but... kibimeters?

2026-04-28 07:05:02 UTC

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@nprofile…ftfu @nprofile…vzdm @nprofile…valu They're half the size if the array is < 65k entries.

2026-04-28 04:00:53 UTC

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@nprofile…xlrs I have survived many years literally writing raw HTML. Which does work! Better than Wordpress :-)

2026-04-28 01:28:18 UTC

What's your favourite static web page builder? Something that takes some form of markup language and splits out some HTML. Nothing fancy, I just really really need to get my (read-only) web page/blog updated. Currently using https://pandoc.org/ which is great, just wondering if there's other options.

2026-04-27 08:32:52 UTC

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@nprofile…j05z The free memory pools is the one place I still use LLs, yeah. I mean - by definition you can't move them, so...

2026-04-27 08:26:32 UTC

It's funny that algo folks still like to talk about linked lists. But these days we avoid them like the plague because they thrash caches and prefetchers.
In the 16-bit era, we didn't have either of those things, so linked lists made a decent amount of sense.
But it's been 30 years! Re-evaluate!

2026-04-25 22:56:11 UTC

Wait wait WHAT. Look, there are many many ways to deal with coordinates starting at the top-left, but this is crazypants.
https://pico-8.fandom.com/wiki/Sin

2026-04-25 20:51:03 UTC

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@nprofile…8xwg Yeah, maybe I'm overthinking it. If they're smart enough to write code, they're smart enough to figure this out. At the same age I started on ZX Spectrum BASIC with its absolutely insane keyboard - so how hard can it be?

2026-04-25 20:02:02 UTC

I've been teaching my nephews programming with code.org and Scratch/Blockly. They're doing great, and at some point I'd like to get them on to TIC80 or PICO8, but I'm a little apprehensive about the sliding blocks->writing text transition. Has anybody done this with kids, and got any tips?

2026-04-25 04:10:42 UTC

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@nprofile…dm5v That's a shame. I knew Hao when he was at Bungie. But I also know a couple of other people who are ex-Lumberyard and yeah that project was a disaster. This might be the best thing that came out of it :-(

2026-04-24 19:24:44 UTC

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Writing C++ code? You should be able to mentally translate this into C. Where are the creator/destructors happening, and what do they turn into? Is that function call virtual? How does that work in practice, and what are the perf implications?
If you're writing C, you really should be able to read assembly, and know what instructions are available, how flow control turns into branches, what a cache line is, what happens when you run out of registers.

2026-04-24 19:24:35 UTC

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So if you're writing Python, you do need to understand what will become a dictionary, and roughly how duck-typing works.
If you're writing a JITted language, you should roughly understand how the JITter works.
If you're writing C# or other managed language, be aware of how the GC works, and you should be able to write the equivalent C++ code without too much trouble.

2026-04-10 21:28:30 UTC

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@nprofile…w2cy Writing OSes is like writing your own language - it's a trap. You will spend a gigantic amount of time on it, and then... it doesn't run anything interesting, and nobody else wants to use it.
Look - I understand hobbies - I really do. But people put way more work in than they would a simple hobby because they dream that these will be useful to someone else. And then they never are.

2026-04-09 22:59:47 UTC

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@nprofile…j05z I have cats for that.

2026-04-07 04:04:39 UTC

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@nprofile…valu @nprofile…w2cy The pupil dilation is effect IS linked between eyes - it's a diagnostic test for brain damage.
The pupil response is almost instant, but is only about a 10x difference. It is not "night vision".
Night vision ("scotopic") is a much slower chemical response of the retina. Not only is it not shared between the eyes, it is local to each part of the retina. It takes much longer - typically about ten minutes. It can adapt to a much larger range of vision (about 1000x).

2026-04-06 21:21:54 UTC

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@nprofile…40t9 Or you could render chunks of the background as texture-mapped triangles at the correct time.

2026-04-06 21:13:59 UTC

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@nprofile…w2cy Also, pilots flying over big cities at night. Shirley at least one of them is a pilot?
In the army, if you're firing up a flare at night, you shut one eye while the flare is up. The eye that stays open will lose its night vision. Then when the flare goes out, you open the other eye, and it still has night vision.

2026-04-03 18:41:49 UTC

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@nprofile…0edt @nprofile…wxct Unit tests just seem like more code to maintain, and more friction to overcome for changes, without doing anything interesting in return.

2026-03-31 21:23:50 UTC

Happy trans folk day of visibility. One thing I am sure of is that people outside gamedev have no idea how many trans folks are in gamedev, and how completely normal it is to have trans folk in gamedev.
I tried to look for statistics, but they all say things like "between 0.3%-3%" which is... what the hell use range is that? Anyway, my local ambient is certainly way higher than that, and specifically in engineering.
So hats off to all my loud and proud trans folks making games! You are legion.

2026-03-30 22:48:42 UTC

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@nprofile…22w0 "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.

2026-03-30 20:49:28 UTC

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@nprofile…d6ud @nprofile…40t9 Ah yes I have done this a few times. Principle Of Most Surprise wins again.

2026-03-26 05:06:02 UTC

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@nprofile…xlrs This is very funny because I grew up in the UK at exactly the right time and yet I never even heard of the Goonies until I came to the US - and I still haven't seen it. So the idea that there's a Speccy game about it is amusing. I suspect it didn't sell well.

2026-03-25 18:18:20 UTC

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@nprofile…d6ud So then for a triangle you should be able to take the total AABB and subtract off the "outer" edge diagonals. You do need to spot the case where one vertex is not in the AABB, and subtract some extra - the blue box:
https://cdn.masto.host/mastodongamedevplace/media_attachments/files/116/291/187/155/255/140/original/65a16290d0012eba.png

2026-03-25 18:05:23 UTC

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@nprofile…d6ud Spitballing, but for each line segment, you should be able to find the area of the AABB (using standard SAT methods) and then divide by two?

2026-03-19 05:37:09 UTC

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@nprofile…6g7u Beet brownies? Like... just beets, or is this a "rock soup" deal?

2026-03-19 04:05:31 UTC

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@nprofile…gd2y Er... whut? Computers are fast. FAST. PCs did all vertex animation in SW until about 2003ish. You should have plenty of juice to SW animate even with C#

2026-03-16 20:36:08 UTC

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@nprofile…5x8e This is clearly garbage, driven by the worst techbro impulses.

2026-03-13 05:47:06 UTC

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There is for sure a clear upper limit to what the average person needs from AI. Just as ProTools got "good enough", just as Photoshop got "good enough", just as VisualStudio got "good enough", the extra features just aren't used by anybody. Once you can fit that locally instead needing the cloud...

2026-03-13 05:46:50 UTC

I found this perspective on AI - as used by "normal" people - to be very informative. Rick undersells his intelligence - but yes while he is (obviously) computer-savvy, he is not immersed in the field like some of us. I think there's a lot of truth here.
https://www.youtube.com/watch?v=YTLnnoZPALI

2026-03-10 18:07:05 UTC

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@nprofile…dm5v Any sufficiently complex bit of asset creation is just programming by another name, and they need to learn the other skills - versioning, maintenance, comments, merging, diffing. Unfortunately all these get rather gnarly in graph-like workflows :-(

2026-03-10 05:39:06 UTC

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@nprofile…kudx @nprofile…d6ud Yeah, the not-so-secret backup plan worked surprisingly well.

2026-03-10 05:29:26 UTC

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@nprofile…d6ud Yeah they kept dicking around and putting 512 in, taking it out, shaking it all around. At one point they were talking about everything having "AVX256" which is AVX512 instructions, but only half-width. It's not *quite* as goofy as it sounds. I think they have now decided not to do that? But yeah it's taking ages.

2026-03-10 05:24:55 UTC

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@nprofile…d6ud I know man, I know :-(

2026-03-10 05:19:45 UTC

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@nprofile…ne33 Why not follow our glorious leader's example and call them a sucker and a loser?

2026-03-10 05:17:24 UTC

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@nprofile…wxct Fantastic - you absolutely deserve it.

2026-03-10 05:14:51 UTC

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@nprofile…d6ud There aren't that many CPUs with AVX but not AVX2 - maybe you can just skip them? Of course what you really want is AVX512 and beyond...

2026-03-08 23:45:17 UTC

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Oh. Oh, that's how (Alt+Shift+LMB to select, then Alt+Ctrl+drag from the selection to the new place). Wow that's really ugly. And I can't flip it when I do?
Tiled does this a lot better - it just becomes the current selection, so you can do the same things as if it was the selection in the tilemap.

2026-03-08 23:30:15 UTC

Really dumb LDTK question. How do I select an area of the level and copy it to another place in the level?
The Help page tells me rectangular select is Alt+Shift+LMB. Sure, that works, great. But now how do I get a copy of that elsewhere? I feel so dumb I can't work this out...

2026-03-08 08:23:21 UTC

Happy birthday to Gary Numan, who is still 13 days older than Gary Oldman.

2026-03-08 01:32:06 UTC

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@nprofile…8q5e This is a completely real story BTW.

2026-03-05 18:50:33 UTC

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@nprofile…3zxe I used it in 1991 or so. They kept upgrading it over time, and the robotape system might have been shared with other systems? My memory is hazy on this.
https://en.wikipedia.org/wiki/Phoenix_(computer)

2026-03-05 10:09:26 UTC

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@nprofile…ds0l
US loser: machine gun.
Dutch hero: glue gun.

2026-03-05 07:22:59 UTC

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@nprofile…yzy8 @nprofile…h98k I never understood why this song was so popular. But it's what we had in the 80s instead of memes.

2026-03-05 07:01:41 UTC

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@nprofile…h98k @nprofile…yzy8
Sorry not sorry :-)
https://www.youtube.com/watch?v=saoH-4SvzXE

2026-03-05 06:57:58 UTC

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@nprofile…j05z @nprofile…7laa Is that the one we physically met at? That was fun.

2026-03-05 05:51:35 UTC

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@nprofile…yzy8 Good to meet you again, Alice!

2026-03-04 19:05:55 UTC

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@nprofile…3zxe Yes it was called "Phoenix" and it had a water-cooled CPU that ran at an astounding TWENTY FIVE MEGAHERTZ. It also had four auxiliary CPUs that handled the actual user I/O. But as a result it could handle up to 300 users at once, and you didn't have to book time slots unless you wanted to do Big Data. Also had a robot tape drive system that I think had a capacity of almost a terabyte? Crazy cool stuff for the time.

2026-03-04 07:48:16 UTC

LTTP but I'm finally watching Casey's talk, and I haven't got to the rest yet but I just love this early story about Bjarne in 1978 at my old university (and indeed on the *same* IBM machine that I worked on!) writing Simula - watch 17:40 to 24:40:
https://www.youtube.com/watch?v=wo84LFzx5nI&t=1060s

2026-03-04 06:37:58 UTC

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@nprofile…6g7u Yeah this is shocking news for someone who has been a lifelong slacker, and who has occasionally been forced to use *xes and hated every one.

2026-03-04 06:31:46 UTC

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@nprofile…7ffg Sorry, Korra denied.

2026-03-04 06:14:22 UTC

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@nprofile…tv2t Actually a bit too recent for me - I was 20 when it came out. Amazing list of stars, including Tone Loc!

2026-03-04 05:35:07 UTC

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@nprofile…3q9y Well... that sucks. Sorry.

2026-03-04 05:23:07 UTC

Me: it's Avatar with beavers.
Wife: what are you talking about?
Me: Hoppers. It's Avatar with beavers.
Wife: yes, I understand the individual words.
Me: <shows the trailer>
Wife: oh. It's Avatar with beavers.

2026-03-03 23:55:06 UTC

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@nprofile…9nma Cats have extremely broad quantum wavefunctions. If you don't observe them constantly, the little buggers will absolutely take advantage. You don't hear any tales about Schrodinger's Dog, do you?

2026-03-03 05:43:12 UTC

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@nprofile…zxj6 @nprofile…3q9y No, but you kicked my memory - the one I am thinking of is Microvania.
https://store.steampowered.com/app/3114890/Microvania/

2026-03-03 04:58:54 UTC

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@nprofile…3q9y There was a "mini" Metroid game recently with I think 6x6 pixel sprites - it was very cute! I thought I bought it, but now I search for it I can't find it. Anyway, it had super cute & tiny graphics - might be a model to look at.

2026-03-03 02:11:44 UTC

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@nprofile…zxj6 They still don't understand the concept of "flat" do they?

2026-03-02 17:59:11 UTC

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@nprofile…t208 I have a talk called "How To Walk" from 2004 here that talks about how I did gait-matching and continuous speed.
https://tomforsyth1000.github.io/papers/papers.html
Also @nprofile…4e67 has done a lot of work in this space and might have some good articles about it.

2026-03-02 09:00:11 UTC

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@nprofile…j05z Real chocolate.

2026-03-01 19:06:45 UTC

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@nprofile…e833 @nprofile…40t9 Rubbish. When has this ever happened before? People yell about cool stuff all the time.

2026-03-01 08:41:23 UTC

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@nprofile…40t9 If they were anywhere near as productive as people claim, those people would appear as gods unto us, and we'd be climbing over each other to use the tech. Instead of having to be tricked into it.

2026-03-01 05:46:43 UTC

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@nprofile…g9kp Well that's his rap name sorted then.

2026-02-28 07:22:42 UTC

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@nprofile…tm4u It is amazing what happens when you let dedicated nerds loose on a problem. Big fan (haha!) of Noctua.

2026-02-28 06:42:00 UTC

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BTW, I do have a whole incoming rant about why, despite having a whole bunch of shooting, and some very interesting and obscure weapons, it has exactly zero pages in IMFDB.

2026-02-28 06:40:26 UTC

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@nprofile…0edt Oh, they were certainly not safe. The finale is quite the gunshow.

2026-02-28 06:39:19 UTC

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@nprofile…0edt Half-way through the season, or the final episode?

2026-02-28 06:17:14 UTC

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@nprofile…tk3a
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!

2026-02-28 06:10:27 UTC

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@nprofile…d6ud We knew about the last episode, saw how long it was, and watched it over three nights. It felt a little less crazy then.

2026-02-28 06:05:40 UTC

Well Sense8 sure went out with a... bang. Very enjoyable series, a proper arc and ending. Really fun and interesting. Exactly the sort of complex plotting I'd expect from JMS, and a big dollop of cinematic strange from the Wachowskis. If you haven't watched it yet, I highly recommend it.

2026-02-28 05:36:01 UTC

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@nprofile…76fl Apparently Hegseth can never be held accountable either.

2026-02-26 18:07:15 UTC

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@nprofile…65q8 Indeed - by the Oliver twins. I believe they're still making Dizzy games!
https://en.wikipedia.org/wiki/Oliver_Twins

2026-02-26 06:26:46 UTC

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@nprofile…6g7u I know you know that's not a broadsword, but you also know I know it alliterates nicely. Touche!

2026-02-25 08:24:33 UTC

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@nprofile…29up You clearly missed a "hell no" tick box somewhere. Or maybe they added yet another secret one. The struggle continues.

2026-02-24 07:47:19 UTC

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@nprofile…s9l9 The people demand answers.

2026-02-23 20:24:49 UTC

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@nprofile…harz @nprofile…40t9 I know a man...

2026-02-23 19:55:04 UTC

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@nprofile…40t9 What you need is a 68000 and some nice alpha-blended sprites.

2026-02-23 10:40:57 UTC

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@nprofile…j459 This man is legit. But it does remind me of this post:
"Humble: #Texans star pass rusher Danielle Hunter still drives an old Nissan he bought over 10 YEARS AGO. He's made +$100 million in his career so far."
Clapped out Cherry? Not exactly. It's Godzilla. 600hp, 200mph, 60mph in under 3 seconds. Hardly slumming it!
https://cdn.masto.host/mastodongamedevplace/media_attachments/files/116/119/501/522/015/068/original/f3c21f539b0b387e.png

2026-02-23 10:11:20 UTC

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@nprofile…8x82 Reminds me of this vid about my previous obsession:
https://www.youtube.com/watch?v=Ts96J7HhO28

2026-02-23 10:06:26 UTC

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@nprofile…s9l9 No fan of AI, but In this case it was specifically asked for advice on rectal use of vegetables. You get what you asssssk for!

2026-02-23 05:05:21 UTC

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@nprofile…nzpc Counterpoint:
https://www.youtube.com/watch?v=oJDGcxAf9D8

2026-02-21 17:54:24 UTC

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@nprofile…f606 @nprofile…0f4l Oh, they don't really. The Amiga tried to, but the 68k has no hardware ability to protect memory, so it's still very fragile. First thing most games did was bop GEM on the head and take over the machine.
But the bombs routine is in the ROM I think? If you don't bother redirecting those exception vectors yourself (and there's no real reason to), you'll still get them. The Amiga was similar with the Guru Meditation error screen.

2026-02-21 09:35:35 UTC

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@nprofile…3vpz If by "highest LOD" you mean the 1x1, then yeah - nothing will fail the alpha test, so you will be writing a lot more values to the shadowbuffer = slower.

2026-02-21 09:32:20 UTC

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@nprofile…3vpz It is completely reasonable these days to have completely separate opacity ("alpha") and albedo ("colour") maps, even if you then use the same UV coords to address both. It can mean you get to use better compression formats, and for things like shadow passes, you only read one of them.

2026-02-21 09:24:05 UTC

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@nprofile…3vpz Do the obvious things - make sure you're not accidentally disabling mipmapping - things like that. You could also try storing the alpha channel as a separate texture, and/or compressing it more aggressively. Also if you don't need really precise crisp shadows, consider putting a mipmap LOD bias on when rendering shadows.

2026-02-21 09:22:14 UTC

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@nprofile…3vpz I would expect shadow passes to be entirely bandwidth-limited. You're doing a very tiny pixel shader, so it's all Z and FB writes.
So adding any texture read that misses the cache - yup, direct perf hit.

2026-02-21 07:07:41 UTC

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@nprofile…yzy8 Just do it two more times.

2026-02-21 07:07:21 UTC

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@nprofile…yzy8 IIRC Nvidia bought almost everything in 3dfx. Whether the EULA transfers depends on the exact wording in the EULA, but it's entirely plausible they now own your ass.

2026-02-21 07:03:39 UTC

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@nprofile…cjqn
<facepalm> Jesus Christ, Denton.

2026-02-20 16:08:51 UTC

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@nprofile…6806 @nprofile…yzy8 I will repeat that git is a database, not a VCS.

2026-02-20 09:36:24 UTC

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@nprofile…3vpz This is a fair point. I write DX11 as the "golden path" because that's what I know best, and then translate to the equivalent OpenGL and ignore all the wacky variants/extensions of OGL that don't directly correspond to the DX11 equivalents. But you could just skip writing the DX11 code entirely I guess? I don't have a broad enough experience of OGL to know if that's wise.

2026-02-20 09:25:27 UTC

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@nprofile…6806 @nprofile…yzy8 Perforce (aka "P4"). IIRC it's free for <10 users.
I have also heard good things about Subversion ("SVN"), though never used it myself.
GitHub is also pretty decent! Not sure how well it scales to big teams, but I like it for small projects that you don't mind being somewhat public. Better than nothing (or git).
I am also watching Ark VCS - it's new, and it is making all the right noises (it's very P4-like at heart), so I'll be excited to see how it develops.

2026-02-20 09:18:53 UTC

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@nprofile…7ffg @nprofile…3vpz The trick is to read ALL the words I wrote, not just some of them.

2026-02-20 09:03:14 UTC

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@nprofile…3vpz If it's just Linux and Windows then DX11 and a matching modern flavour of OGL still work perfectly well, and I prefer the balance of how much work I have to do versus what the driver does for me.

2026-02-20 08:41:50 UTC

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@nprofile…7ffg @nprofile…yzy8 I'm comfortable with you being wrong. Git is a fundamentally broken model and scales like dogshit.

2026-02-20 08:36:25 UTC

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@nprofile…3vpz What platforms do you need to support? Vulkan is a lot of typing, but e.g. if you need to also support DX12 and Metal it's pretty much the same "a lot of typing". Or yeah use a thin engine like BGFX or something.

2026-02-20 08:16:28 UTC

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@nprofile…7ffg @nprofile…yzy8 I know how a good RCS should work. And I know how git works. And the two are very very different. Git is a database, not an RCS. If you wanted, you could build a perfectly good RCS on top of git (and you can argue that GitHub is that thing).
But raw git - it's not the right model. It's like booking your plane flight by writing SQL directly into Alaska Air's database. You can make it work, but...

2026-02-20 08:12:03 UTC

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@nprofile…7ffg @nprofile…yzy8 Oh my mental model of git is perfectly good I assure you. That's how I know it's absolutely not what anybody should ever use.

2026-02-20 08:00:22 UTC

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@nprofile…zhjz
https://cdn.masto.host/mastodongamedevplace/media_attachments/files/116/101/899/755/586/183/original/9f072a1693bb0c74.png

2026-02-20 07:58:26 UTC

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@nprofile…yzy8 I lasted 30 years without having to touch git. And then I had two horrific years were I had to touch git. And now I'm out again, cleansed and purified from the stench, and it is so so sweet.