Burst Acceleration
UModeler X runs its heaviest editing routines as Burst-compiled parallel jobs. What is accelerated today, how to enable it, and what the turtle icon means.
From 1.4.0, UModeler X can run its heaviest editing routines through Unity's Burst compiler as parallel jobs instead of single-threaded managed code.
The goal is responsiveness on meshes that used to get sluggish — dragging a large selection, rectangle-selecting across a dense model, isolating a group, or opening a scene full of editable meshes.
Requirements
Acceleration needs two Unity packages:
| Package | Id |
|---|---|
| Burst | com.unity.burst |
| Mathematics | com.unity.mathematics |
If either is missing, a turtle icon appears in the Scene view toolbar. Click it and UModeler X explains what is wrong and offers to install the packages for you.
Turning it on and off
Go to Edit > Preferences > UModeler X > Performance > Burst Acceleration. It is on by default.
Changing this option reloads scripts. The acceleration hooks are registered during domain reload, so the switch cannot take effect until the reload finishes. Turning it off leaves the Burst files compiled but unhooked, and every routine falls back to the managed path.
See Preference for the rest of the Performance options.
What is accelerated today
Coverage is deliberately focused on the element editing hot paths — the loops that run once per vertex, edge, face or loop, where element count decides the frame time.
Editing elements
- Moving, rotating and scaling elements — the vertex coordinate pass runs as a parallel job, and so does the setup pass that walks vertex-incident faces and collects face loops.
- Preserve UV — the UV compensation applied while coordinates move.
- Snap — collecting vertex, edge-center and face-center candidates, and projecting them to screen space.
- Sculpt brushes — Move, Pinch, Flatten, Standard and Smooth, plus the vertex normal recomputation they depend on, and the neighborhood backup taken before a stroke.
- Batch face creation — radial and disk cycle linking.
Display and picking
- Overlay building for vertices, edges, faces and the UV overlay. Overlays are written straight into GPU buffers, and only the blocks whose coordinates changed are re-uploaded instead of the whole buffer.
- Picking moved from GPU ID rendering to a CPU BVH — hover and click picking for vertices, edges and faces, plus rectangle and capsule selection.
- UV Editor picking uses a uniform grid instead of walking every face.
- Selection math — isolate groups, UV islands, and the selection center and bounding box used by the gizmo.
Loading and building
- Mesh asset deserialization — vertex, edge, loop, face and UV pools, and vertex colors.
- Structure validation that runs on every load.
- Mesh cache and renderable mesh build, normal and tangent computation, and large buffer copies.
Where you notice it
The speedup comes from three places:
- Parallelism — per-element loops that ran on one thread are split across CPU cores.
- Native code — Burst compiles the job to SIMD machine code, with no per-element managed allocation for the garbage collector to clean up afterwards.
- Less upload — overlays send only the changed blocks to the GPU rather than rebuilding and re-uploading whole buffers.
All three scale with element count, so the gain does too. On a light mesh the managed path was never the bottleneck and you will not see a difference. The heavier the mesh and the more elements an operation touches, the larger the gap — and the operations that benefit most are exactly the ones that used to stutter: dragging a big selection, rectangle-selecting across a dense model, isolating, and loading a scene full of editable meshes.
Not accelerated yet
These still run on the managed path:
- Modifiers
- Parametric Shape rebuilding
- UV unwrapping
- Painting (2D and 3D)
- Boolean and other Multiple Objects operations
- Import and export
Coverage widens release by release. Each routine is moved across an isolated seam that keeps the managed implementation in place, so a newly accelerated routine produces the same result as before — which is why the list can grow without changing how anything behaves.
When the turtle icon appears
The icon is shown only while acceleration is not running. Click it for a dialog that names the cause and offers the fix.
| Cause | What it means | How to fix |
|---|---|---|
| Packages not installed | Burst or Mathematics is missing | Install them from the dialog |
| Acceleration not loaded | Packages are present but the scripting define is not set | Enable it from the dialog — it adds the define and reloads scripts |
| Turned off in preferences | You switched it off yourself | Preferences > UModeler X > Performance > Burst Acceleration |
| Unity Burst compilation off | Unity's own Burst compilation is disabled | Jobs > Burst > Enable Compilation |
| Internal layout mismatch | A defect, not a setting — acceleration disabled itself to stay safe | Check the Console for the error logged at startup |
Every dialog also offers Turn Off Burst Acceleration. Choosing it hides the warning for good and keeps you on the managed path, which is the right answer if you would rather not install anything.
See also — Preference · Toolbar · Troubleshooting