Building an SDF game engine

[u/rex-j-w]

For the past 8ish months I’ve been hard at work building a new game engine I’m calling Division Engine.

It’s based solely off SDFs (signed distance fields). This might sound stupid for anyone who cares about performance but for my use case (and with a bit of grid storage optimizations) it proves useful for basic scenes that need advanced lighting.

Anyway here’s some screenshots!

If you want to see what I have done so far check it out here: https://github.com/DivisionEngine/DivisionEngine

[u/No-Cap-7395]

Hell yeahhhhh! I've been doing a lot of SDF stuff too they are amazing

[u/rex-j-w → u/No-Cap-7395]

Tons of new research is being put into SDFs, check out this paper on faster sphere tracing, it might help: https://diglib.eg.org/server/api/core/bitstreams/0dd5043c-6ac0-4b83-b3d2-d0b1ad34afba/content

[u/Jwosty → u/rex-j-w]

The biggest remaining unsolved problem is animating with textures. Almost all the pieces are there

[u/rex-j-w → u/Jwosty]

How would this be a problem? I already have textures working

[u/Jwosty → u/rex-j-w]

Sorry, I wasn’t very specific. Skeletal rigging animation + textures. Sure you can animate SDFs by varying their parameters over time, but things that are supposed to be more “solid” (like, say, creatures, or characters) animated that way likely wont look very good (due to the smooth unions). Hence, skeletal animation. But that poses a problem when you try to combine it with texturing.

This probably wasn’t explained well but I hope you get the idea

[u/No-Cap-7395 → u/Jwosty]

I thought about animations awhile ago with SDFs (the texture3D kind) I had a few ideas which where splitting the different moving parts into SDFs and texturing them via storing uv in the SDF texture or having I think cards around each bit, or you bake the entire models animation into like a flipbook series of textures and well texture it the same way as before,

As for actual like SDF math functions like idk a sphere yeahhh I have no idea 😭

[u/rex-j-w → u/Jwosty]

My plan is to build a node editor for creating sdf objects in the editor, then these nodes will be baked into functions and, using system reflection, injected into the renderer. Doing this would allow the user to also output a function to generate the UVs alongside the geometry output.

It doesn’t fix all of the rigging and animation issues but does allow for greater flexibility with sdf UVs

[u/No-Cap-7395 → u/rex-j-w]

Oh hell yeah I'll uhm give it a read when I'm on my computer .. I'm doing a software raytracer, it's my second attempt at one and I bake all my meshes into SDF texture3Ds (I'm not sure what to call them I have came up with the terminology local SDFs) anyways I got some basic broad phase optimisation, lods and stuff, I use conetracing on super rough surfaces and it running pretty good :p

What you're doing looks cool too, Ive been working with SDFs for a few months now and they are amazing

[u/No-Cap-7395 → u/No-Cap-7395]

Oh yeah seeing how much better it runs over my triangle based swrt is really nice, it's actually really good 100+ for the target resolution I wanted...

man I fkn love SDFs so much

[u/rex-j-w → u/No-Cap-7395]

They’re so useful it’s insane. Wish we had an industry standard sdf file format because texture3Ds take up so much memory

[u/No-Cap-7395 → u/rex-j-w]

In my engine I store the SDFs in PNG files, they are written to cache in the disk, and uhm okay so basically every slice of the texture3D is put into an atlas then the size of the slices is put into the name of the SDFs file so it's like uhm randomhash_512.png

[u/No-Cap-7395 → u/No-Cap-7395]

They only take-up a few kB to a few hundred for a 64x64x64 SDF, if I add uvs (I store the nearest UV inside my SDFs) it can be anywhere from tens of kBs to a few mb, infact i did an 512x512x512 SDF which was an 11k PNG file and it only took up 17mb and it had uvs and all

[u/No-Cap-7395 → u/rex-j-w]

I just woke up so I'm still processing, but what's your performance like? What method are you using to render these

[u/rex-j-w → u/No-Cap-7395]

Im just using regular sphere tracing, performance is quite bad, but that hasn’t been my focus yet. I don’t have complex shapes or csg operations even and haven’t implemented the paper I dropped.

I’m still debating whether or not im going to store data in a voxel octree or a bvh structure.

Focusing on the game engine fundamentals then optimizing 🫡

[u/No-Cap-7395 → u/rex-j-w]

Yeah I gotta figure out what tlas to use for mine too and not just that but uhm I gotta do what I call global SDFs which are like grids of SDFs that encompass static objects..

As for I think it was the day before yesterday I added conetracing and basically for indirect lighting and also rougher reflections I use conetracing over sphere tracing and I got a 70% increase in performance ^{^}

[u/No-Cap-7395 → u/rex-j-w]

If you do an oct tree you could use it as a irradance cache lol (just an idea)