Hi all,
I’ve hit what looks like a regression and wanted to check whether anyone else is seeing it. Symptom
Models imported with Settings → Asset Import → Mesh Compression = Draco never render in the viewport. The exact same file with Mesh Compression = Disabled renders fine. I’ve been using Draco for months with unchanged parameters, so this started after a recent update. Repro (3 steps)
Set Mesh Compression = Draco
Upload an FBX (exported from 3ds Max) or a GLB
Add it to the scene → nothing renders
Pressing F to focus the entity and resetting scale to 1/1/1 change nothing. The Console stays clean — 0 errors, no warnings. The Inspector still shows correct stats (4298 vertices, 2848 triangles, 2 meshes) and the materials are mapped. Already ruled out
Entity transform / scale; F-key focus; layer configuration; preload flag; Render asset assignment; asset type (glb vs render asset vs template); 3ds Max export settings. The only variable is the Draco toggle, and it reproduces every single time — which rules out the model file itself. The detail that seems most telling
Mesh data is readable (correct vertex/triangle counts) but no mesh instances render, and nothing is logged. That points to the Draco decoder failing silently rather than the file being broken.
Possibly related to recent decoder changes: #8951 (Draco decoding via worker_threads), #9656 (keep Node worker_threads require out of bundled worker code), #8868 (warn and fail when the Draco decoder is unavailable), and the still-open #9373 (evaluate minidraco as an alternative to the WASM Draco decoder). Environment
Editor 2.35 (released 2026-10-21) / Engine 2.23.3, Windows, Chrome 134.0.6998.89 and Edge 156.0.4314.42. Workaround
Mesh Compression = Disabled. Works, at the cost of larger files. Two questions
Is anyone else hitting this?
Is there a way to point the Editor at a locally hosted Draco decoder, as a temporary workaround?
Happy to share a repro file and a project link if that helps. Thanks.
I’ve tried to reproduce this on Editor 2.35.3 / Engine 2.23.3 (Chrome) with Mesh Compression set to Draco, and so far I can’t. I imported a few GLBs and FBXs, including skinned meshes, morph targets, vertex colours and multiple UV sets, with containers both on and off. All of them decoded and rendered in the viewport and in Launch, including after reloading the scene.
On the decoder question: the Editor viewport loads its own copy of the Draco decoder, not the one in your project. Hosting a decoder yourself wouldn’t change what the viewport uses, so disabling compression is still the best workaround for now.
To narrow it down, could you share:
One of the files that comes in invisible (you offered one, that would help most), and a link to the project if you can make it public
Whether Draco models you imported before the update still show up, or whether only new imports are affected
Whether the invisible model shows up when you launch the scene
Your Draco Decode Speed and Draco Mesh Size values (Settings → Asset Import)
Anything in the Chrome DevTools console with the level set to show all messages (Verbose included), not just errors
Once I have a failing file I can look at it directly.
Hi @KPal, thanks for looking into it — good news, I managed to narrow it down considerably.
1. Old vs new imports Draco models imported before the update still render fine. Only newly imported assets are affected.
2. The trigger appears to be the “Draco Decode Speed” value With Decode Speed = 1 (my original setting), every new import is invisible. Changing Decode Speed to 0.9 and re-importing the exact same file makes it render correctly, 100% reproducible both ways.
3. DevTools console (Verbose) shows errors that the editor’s Console panel never surfaced
Failed to access two assets ... (container) ... Failed to decode draco asset
Repeated many times during import: Error processing XMLHttpRequest (response: InvalidStateError: Failed to read the 'responseText' property from 'XMLHttpRequest': The value is only accessible if the object's 'responseType' is '' or 'text' (was 'arraybuffer').
The second one looks like a request/response handling bug: the XHR is set to arraybuffer but something then reads responseText, which throws. Possibly related to the failed decoder/asset fetches.
Hi @dou2499859604, thanks for the file. It let us reproduce this straight away.
What’s happening: a recent update fixed the Draco Decode Speed setting, which before that wasn’t being applied at all. Now that it works, a value of 1 tells the importer to use Draco’s fastest-decoding mode. The Draco decoder the Editor currently ships can’t read that mode for some meshes, including yours. So the import succeeds, but decoding fails and the model comes in invisible. That’s also why it only affects new imports, and why 0.9 works.
What to do for now:
Set Draco Decode Speed to 0.9 or lower in Settings → Asset Import.
Re-import the models you imported with it set to 1. Those files won’t recover on their own.
Models you imported before the update are fine, and you don’t need to change anything else in your project.
Speed 1 also produces much larger files for very little gain; your model was about 3× the size of the 0.9 import. A lower value is the better choice anyway.
What we’re fixing: we’re updating the Draco decoder and adding checks so the importer can’t produce files the shipped decoder can’t read. We’ll post here when that’s out.
Thanks again for narrowing it down so precisely. The settings comparison and the file made this quick to pin down.
Thanks again for the file, it made this easy to track down.
A fix is now live. Draco Decode Speed 1 now produces the same output as 0.9, so new imports at any setting will load in the Editor and in Launch. You can set the slider back to 1 if you prefer, but it no longer changes anything compared to 0.9.
Models you imported at 1 before the fix still need re-importing. Re-import the source FBX, or right-click it in the Assets panel and choose Re-Import.
We’ve also made the Editor console report assets that fail to load, so a problem like this shows up there instead of only in the browser DevTools.
