does anyone have any idea how build engine 'voxel sprites' worked? based on my research they appear to be in .kvx format and Ken Silverman later made an editor (early oughts) called slab6. but i can't find any technical information about how they actually were rendered in-engine. - ThreadSky

lorenschmidt.bsky.social • 14 days ago

does anyone have any idea how build engine 'voxel sprites' worked? based on my research they appear to be in .kvx format and Ken Silverman later made an editor (early oughts) called slab6. but i can't find any technical information about how they actually were rendered in-engine.

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pixelmusement.com•13 days ago

You COULD just ask the man himself; his contact details are at the bottom of his website. ;)

https://www.advsys.net/ken/

lorenschmidt.bsky.social•13 days ago

ok i am getting stage fright but i do have a rule that you should always treat famous individuals like normal people instead of being weird about it...

jdespland.bsky.social•13 days ago

silverman's "voxlap" engine is open source but i don't know if it's the same method as the build engine voxels

lorenschmidt.bsky.social•13 days ago

yeah i wonder- maybe some simpler relative with more restrictions? like pinned to one axis.

liasae.bsky.social•13 days ago

I’m guessing it’s not covered in the Graphics Programming Black Book? Different guy but about the right time

lorenschmidt.bsky.social•13 days ago

oh hmm! i don't know that, but it seems like the only window where CPU voxel techniques would exist in that space!

darzu.bsky.social•13 days ago

.vox is popular too. I work on an engine with a .kvx and .vox importer. We convert it to a 3D texture and render it using ray tracing / dda. We tried some other approaches like generating slice planes but ray tracing is faster. For big files we chunk to 64x64x64, or use oct tree

darzu.bsky.social•13 days ago

Oh i didn’t realize “Build” is a specific engine. I don’t know what they do.

lorenschmidt.bsky.social•13 days ago

interesting! so what are the bottlenecks? i know voxels can be tricky in SDF renderers. so you're actually doing 3d DDA instead? and what's the splitting about, is that to reduce overhead? or to parallelize?

lorenschmidt.bsky.social•13 days ago

and it was a CPU solution- i think Blood is the best known game with voxel sprites in it, but there were others as well. they look really good! i'm very curious about how they did that performantly.

whizzter.bsky.social•13 days ago

Iirc it’s an logical extension to old-school terrain renderers, basically you scan from the bottom per-column, you keep track of screen Y(=max from bottom) and world position. For each step you calc a new screen Y from the world heightmap pos and do an y-fill between prev and current.

whizzter.bsky.social•13 days ago

Iirc if your viewport isn’t rotated, then you prob can adapt this to render axis aligned voxels that are more arbitrary with holes (if the holes becomes ”portals”)

lorenschmidt.bsky.social•13 days ago

i could see that fitting! how does the convex underside work?

from what i've seen the shapes seem like they might be constrained in some way- limited overhangs and layered parts?

darzu.bsky.social•13 days ago

Yeah 3D DDA, pretty close to how Teardown does it:
https://acko.net/blog/teardown-frame-teardown/

64^3 is just to cap the max number of steps any thread needs to take. I haven't investigated how important this is. We run at 360p for stylistic reasons, and worlds with 4000 chunks is <20us so our bottlenecks r elsewhere.

darzu.bsky.social•13 days ago

Here's a heat map showing how many steps were needed per pixel. Rainbow wraps after 64 steps.

We also have an oct-tree renderer that we're thinking we'll use for very large levels but i'm not actually sure it'll be faster.

lorenschmidt.bsky.social•13 days ago

looking at this again- so the ground and walls are riding at like, sub ten steps? and they're fully voxel? that's incredible.

darzu.bsky.social•13 days ago

If we needed it to be way faster I would create a mip-like pyramid for each model w/ 1 bit per voxel, like Teardown does

eniko.bsky.social•13 days ago

i looked into it but could also not find anything about it. apparently voxel sprites in i think zdoom use the same code and last i checked nobody knows how it works there either :|

dude27th.bsky.social•13 days ago

Oh afaik GZDoom doesn't support them as is, but they are converted to 3D models at runtime

lorenschmidt.bsky.social•13 days ago

i saw someone talking about that! ok, so they end up as polygons?

stupidhoroscope.bsky.social•13 days ago

I did a little investigation into this a while ago, and it appears they just render points for each voxel, which scale with distance, and does some kind of backface culling.

Code is here, although it's exceptionally hard to read.
https://github.com/fabiensanglard/vanilla_duke3D/blob/05ba48edb2da5b3256736039b03a853e1ea0ceef/SRC/ENGINE.C#L3944

stupidhoroscope.bsky.social•13 days ago

(I should note that my 'investigation' was mostly just observing how the voxels behaved in-game, every time I tried to look at the source I just end up going 'Yknow what, I've got better things to do with my time')

lorenschmidt.bsky.social•13 days ago

oh if that's the case, perhaps it's what folks now call 'splatting'? i want to get a copy of blood or something and stare at them now...

taconite.bsky.social•13 days ago

I think it's similar to gaussian splatting in that every voxel gets a billboard.

In GS they're 3D gaussians (or better yet SH for anisometric), but in this case they just look like quads.

stupidhoroscope.bsky.social•13 days ago

They definitely would've been quads. Or to be more specific, more analogous to sprites, since in software-rendering days it would've just been setting the pixels directly to the color of the voxel in an on-screen rectangle.

lorenschmidt.bsky.social•13 days ago

i was kind of hoping it would be a mini raycast screen region or something like that! but that makes sense.

stupidhoroscope.bsky.social•13 days ago

Hahah that's exactly what I did, basically jumped into E1M1 of Blood and just crouch-walked around the voxel gravestone right at the start of the level.

You can slightly poke your head through it, and it helps show how they did it.

stupidhoroscope.bsky.social•13 days ago

Although keep in mind; most modern ports (Including the Nightdive one) just turn the voxels into models, treating each voxel as a cube. Blood: Fresh Supply (Nightdive port) on the left, DOS original on the right:

stupidhoroscope.bsky.social•13 days ago

I'd take better shots (You can tell the point-like nature better near the base), but the original Blood doesn't have hold-to-crouch so it's hard to take a screenshot.

But yeah, grab the Blood shareware version, Dosbox, and have a look!

https://archive.org/details/Blood_Shareware_04-12278CD_Monolith_Productions_1997

tarwin.art•13 days ago

I'm guessing these won't in Duke 3D right ? Only in later ones like Blood ?

lorenschmidt.bsky.social•13 days ago

i think duke didn't use them but i'm not 100% sure

tarwin.art•13 days ago

Yeah Ken's stuff says Shadow Warrior and Blood it seems.

https://advsys.net/ken/download.htm

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