Use as custom Mapbox layer (without regl)

[carderne]

I've been playing around a bit with this code to see how feasible it would be to use most of the pipeline to create a custom Mapbox WebGL layer rather than a completely separate canvas rendered underneath a Mapbox layer.

The advantage of this (to my mind) would be that you could more easily interleave zarr layers with Mapbox layers, control visibility/opacity together with Mapbox, and potentially more easily build it out as a library rather than a framework as it currently is?

Would need to pull out regl, as afaict it doesn't support WebGL2 (which Mapbox requires).

I'm going to keep tinkering, but I thought I'd share this idea as I barely know my way around WebGL so may take a while!

[carderne]

For what it's worth, I have this working here:

https://github.com/carderne/zarr-gl

It's very basic currently, but I plan to add most of the missing functionality soon (and make it less janky!).

[Shane98c]

This is so cool to see!

Another pain point that this potentially helps with is escaping web mercator - it seems like custom layers might be able to render on mapbox's globe view (tho not their other projections for the moment)? Maplibre has a globe view coming as well so it'll be interesting to see whether custom layers are supported there too!

We've had something like this on our maps bucketlist for a while but haven't had capacity to iterate on this project (as you can maybe tell from our issues page!). It's so exciting to see such quick progress on this - we'd love to figure out how to help out! Some initial thoughts:

• We were able to get regl working with webgl2 with some tricks here: webgl2 #126
• We've been meaning to try using zarrita.js instead of zarr-js because the former is better maintained and likely to become the official zarr JS client.
• We've also played with the idea of using webgl to render out z/x/y raster tiles from zarr on the client (basically client side titiler) which would get us more flexibility with projections/mapping libraries but probably at the expense of performance/smoothness

We're very excited to keep playing with zarr-gl and to see how it progresses. Thanks for reaching out!

[carderne]

Hey @Shane98c thanks for this!

• Custom layers in Mapbox Globe: found that same thread, haven't yet investigated how it might work. Docs suggest that the data still needs to be in mercator coordinates...

• Regl with webgl2l: yeah I noticed just a bit too late that you'd figured that out. I haven't really used WebGL enough to know what I'm missing out by not using regl, but zarr-gl is still very little code so I figure not too much?

• Zarrita: I actually switched back to zarr-js temporarily because the build output had all the blosc/lz4 stuff lumped in and wanted to figure out what was going on there before sticking with it. Haven't done any performance comparisons but presumably minimal. Definitely types are nice.

• Projecting on the client: I started googling about this, bunch of interesting stuff from Bostock. Maybe some Rust decompression + zarr + reprojecting compiled to WASM would make this feasible, don't have a great grasp of the order of magnitude of performance hit... This would be amazing though.

Anyway I'm going to keep slowly noodling. I need to add support for selector and improve the logic around choosing tiles to load/retain, and then it should be relatively useable.

[carderne]

Oh and the other reason I switched back from zarrita: it seems to have some important metadata as private class fields. Haven't yet reached out to the devs to properly understand this.