Validating a layered accessory inside Blender, before exporting

The most expensive cycle for anyone producing layered accessories for Roblox is not modelling. It is the back and forth: export, import into Studio, take a validation error, go back to the modelling program, adjust, export again. Every round costs minutes, and some cost the upload fee.

Roblox distributes a tool that cuts part of that cycle — and it is surprisingly little known for something official, free, and running inside the program where the work happens.

The problem

The layered accessory validation tool installs into Blender or Maya, and it is there to identify and quickly fix the common problems of layered accessories before export.

The proposition is direct: it saves time in the typical back and forth between the 3D modelling program and Studio. Instead of discovering the problem at the end of the pipeline, you discover it with the model open and the whole scene to hand.

And here comes the caveat the documentation makes a point of repeating — it appears twice on the same page, at the beginning and at the end. The tool checks only the common problems of layered accessory creation. Even with it, the model has to meet the general mesh requirements and the layered accessory specifications before it goes into Studio.

That is worth reading carefully, because the consequence is counterintuitive: green in the tool is no guarantee the submission is accepted. It is triage, not a substitute. Anyone treating it as a substitute will pay the upload fee trusting a signal that never promised that.

There is also a version note that decides whether the effort is worth it: the tool was designed for Blender 3.0 and Maya 2022. And there is a freedom almost no official tool gives — you can download and modify the tool for any use. For anyone with their own pipeline, that changes what is possible: the checks can become part of an export script of your own.

Step by step

There are two files and two sets of instructions, one for each program. There is no single installer, and the two experiences differ considerably in difficulty.

In Blender, the route is the ordinary add-on one. Download the .zip and do not unzip it. Under Edit, then Preferences, go to the Add-Ons section in the left sidebar, click Install..., choose the .zip and confirm.

Then comes the step most people skip: after installing, you have to find the Validation Tool in the list and enable the add-on. Installing does not enable — they are two actions, and the second is a checkbox that is easy to miss.

Finally, go back to the workspace and expand the viewport sidebar. That is where the tool lives. Without expanding, everything looks as if it went wrong when in fact it went right.

In Maya, there is a prerequisite: you have to install Python 3.0 or above before the tool. And in the Python installation there is a checkbox that decides the success of everything after it — ticking the option to add Python to the PATH before clicking install. Without it, the tool's installer does not find Python, and the error message will not say so.

Then download the tool's .zip and unzip it into a local directory — note the difference from Blender, where the zip stays closed.

On Windows, it is a double-click on install.bat. On Mac, right-click install.command and open with Terminal. If the Mac refuses for permissions, the documentation gives the exact command: navigate to the directory and run chmod 777 install.command. That step requires administrator access.

When asked, type the Maya version — if you use the 2020 one, type 2020.

To use it: on first use, open Windows, General Editors, Script Editor, type import ValidationTool and click the Play button. On later uses, the command is ValidationTool.validationTool(), also with Play. You can create a Maya shelf shortcut through the tool's own interface.

Running it, in both programs: select the object in the scene, open the tool and click Check Assets. After a few moments the interface updates and produces an output message, with the problematic results highlighted.

The difference in effort between the two installations is worth noting, because it influences the decision to use it. In Blender it is five steps, all inside the program, with no external dependency. In Maya it is twice that, with Python, an environment variable, an installer per operating system and, on Mac, a permissions command. It is not that one is better — it is that, in Maya, it is worth setting aside time for the installation rather than trying to fit it into the middle of a project with a deadline.

The artifact

The list below is the installation and usage script for both programs, in checklist form, with the most forgotten steps marked.

It is mainly worth it for Maya, whose installation has an external dependency, an environment variable, two different installers by operating system and a permissions command. It is the kind of sequence in which a skipped step produces a failure whose message points at the wrong place.

At the end of it is, once again, what the tool does not do — because that is the part people forget after two weeks of using it.

Common mistakes

The most common mistake is reading the colours, and it is specific to anyone who uses both programs or learned in one and moved to the other.

The conventions are different. In Blender, a result with a problem is red and a check with no problem is grey. In Maya, a problem is yellow and no problem is green.

Blender's grey is what catches people. In almost every interface, grey means disabled, not evaluated, not applicable. Here grey means passed. Anyone arriving from Maya looking for green finds an entirely grey screen and concludes the tool did not run — and goes looking for what is wrong with the installation.

The second mistake is not taking advantage of the automatic fix. Some failed checks are resolved by clicking the check's own button, and some problems are fixed automatically at the highlighted button. It is easy to look at the red list, sigh, and go back to the scene to hand-edit what one click would have solved.

The caveat is the usual one with automatic fixes: it changes your model. It is worth running it with the file saved, checking the result visually afterwards, and not chaining five automatic fixes without looking at what happened in between. A fix that resolves the check and ruins the silhouette still shows as resolved in the list.

The third mistake is about versions. The tool was designed for specific versions, and Blender and Maya are programs that change API between major versions. If it does not appear, does not open or fails with a Python error, the first question is which version you are using — not what is wrong with the model.

And the fourth is the most expensive: trusting the green. The tool is triage for common problems. An accessory that passes it can still fail Studio validation on geometry, texture, cage or attachment — exactly the categories the full validation examines and that this one does not promise to cover.

Next step

The use that pays most is bringing the tool in early, not at the end. Running Check Assets right after closing the mesh, before texturing, catches geometry problems while they are still cheap to fix — after painting, redoing the topology costs the texture too.

After that, it is worth considering the freedom the licence gives. Since you can download and modify the tool for any use, anyone with their own pipeline can build the checks into an export script — so that leaving the scene already means having passed triage, with nobody needing to remember to click.

It is also worth combining the tool with the habit of keeping a clean test scene: a file with only the accessory and the reference body, nothing else. Running the check in a scene full of old objects produces a result that depends on what is selected, and that is the kind of variable that turns objective triage into an impression.

And, whatever the tool says, the specifications remain the source of truth. Reading the layered accessory one once, in full, is what turns "red on check X" into "ah, that rule" — and it is what the tool, by design, is not going to teach you.

LAYERED ACCESSORY VALIDATION TOOL
Designed for Blender 3.0 and Maya 2022. Checked on 23/09/2026.
There are TWO files and TWO sets of instructions — there is no single installer.

== BLENDER ==

[ ] download the add-on .zip and save it locally (do NOT unzip it)
[ ] Blender > Edit > Preferences
[ ] Add-Ons section, in the left sidebar
[ ] Install... button -> select the .zip -> Install Add-On
[ ] find "Validation Tool" in the list and ENABLE the checkbox
    ^ the most forgotten step: installing does NOT enable
[ ] go back to the workspace and EXPAND the Viewport sidebar
    ^ the tool lives there; without expanding, it looks like it did not install

== MAYA ==

Prerequisite: Python 3.0 or above.

[ ] download the installer from the official Python site
[ ] TICK "Add Python ### to PATH" BEFORE clicking Install Now
    ^ without it, install.bat / install.command does not find Python
[ ] download the tool's .zip and UNZIP it into a local directory

Windows:
[ ] double-click install.bat

Mac:
[ ] right-click install.command > Open With > Terminal
[ ] if it refuses for permissions (it needs administrator access):
      cd <install.command directory>
      chmod 777 install.command
[ ] when asked, TYPE the Maya version (e.g. 2020) and Enter

First use:
[ ] Maya > Windows > General Editors > Script Editor
[ ] type:  import ValidationTool     -> Play button

Later uses:
[ ] type:  ValidationTool.validationTool()   -> Play button
[ ] optional: create a shelf shortcut through the UI's shortcut button

== RUNNING ==

[ ] select the object in the scene
[ ] open the tool and click Check Assets
[ ] read the result:
      Blender: RED    = problem, GREY  = no problem
      Maya:    YELLOW = problem, GREEN = no problem
[ ] some checks are resolved by CLICKING the check's own button

== WHAT IT DOES NOT DO ==

It checks ONLY COMMON layered accessory creation problems.
It does NOT replace Studio validation or the specifications. Green here is
no guarantee the submission is accepted — it is triage before export.