STEP import

I’m using

UV Toolkit for Blender 2.8x

and Rizom UV as an external solution via headus uv bridge.

Edit: Just found Zen UV, which looks pretty interesting too:


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I tried RizomUV but it didn’t do a better job unwrapping complex models automatically. It’s just a bit faster. But not worth the extra money in the end for me.

The UV Toolkit just seams to use Blender technology and makes some procedures easier. That might be useful for models where you still have control over the UV islands, but for complex models it doesn’t bring anything new to the table either I guess.

Tja Andreas, dann weiss ich auch nicht mehr weiter :slight_smile:

Did you join Rizom’s Discord Channel? Rémi might help over there.


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I’m facing the same problems currently. Usually we are doing CAD-work in 3ds max for offline rendering, where I hardly ever use UVs (and am mostly relying on triplanar mapping and bevel shading).

But now we are trying to use CAD data in realtime applications, so I’m reducing them to around 100k - 500k faces (the STEP Import plugin for Blender makes this a lot easier already - 3ds max can’t go that low). Baking lightmaps or ambient occlusion is a must then, but with them consisting of so many objects, I’d have to rely on an automated unwrapping solution for most of them. Blender’s automatic unwrapping (smart UV) is already a lot better than what 3ds max has to offer out of the box, but as mentioned above, it produces some overlapping and flipped UVs (especially on mirrored instanced geometry). Also it splits up a lot of the smaller details into single polygon islands, which - once you add padding - wastes a lot of UV space.

I’d also be interested in better (automatic) unwrapping solutions that can deal with high polygon counts. Having this inside Blender would be a plus.

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Here’s the kind of model that is really hard to unwrap. It’s a fighter jet (downloaded from GrabCAD), imported to Blender with the STEP import plugin. Feel free to try and let me know if you find a good and quick way around it. Much appreciated.

It would already be a great help if the unwrapping tools in Blender were a bit faster. For example the Smart Unwrap tool seems to use just about 10% of CPU power on my PC. For the fighter jet model that I mentioned in the post before, Smart Unwrap takes about 10 minutes to do the job. Lightmap Pack (although being hardly usable) takes several hours to complete. If at least Smart Unwrap were a bit faster, trying out several angles would be easier and more productive.

Well in fact stepper already gives you the seams.
So in most cases you just have to make a regular unvrapp (conformal option is better for non-organic shapes).
Then you can you a plugin like :

In order to keep a constant “texture zoom” on your models.

It would be helpful if there was a way to select all screw holes automatically, as those could clearly be deleted. Unfortunately none of the “select similar” options in Blender work - neither in Edit mode, nor in UV mode.

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Don’t worry about those screw holes. I quickly deleted the seats and of course there’s still some stuff in there that isn’t really needed. The original model had 600K polys which was a bit of an overkill. But in pretty much every other model there’s something similar that actually can’t be deleted.

I DO worry about them, because they take up a huge amount of UV space (since they are tiny, each of those pieces gets the respective UV padding around them). They need to go!

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I’m packing the UVs with Packmaster in the end anyway. And as I said - this was the first model I found on GrabCAD and just some example of a similar scale that I usually have to deal with. It’s more about all the overlapping and self-Intersecting UVs one gets with models of this complexity. And once you have to paint those models, things get pretty nasty.

@ambi Do you have plans of making any updates to this addon or about to leave it as it is? In case you are not making updates, would it be possible for users to modify themselves? I’m thinking of few usability tweaks and meshing improvements mentioned here. I haven’t looked addon files if it’s modifiable directly or would need some source files from you.


Yes, I still intend to develop it. It’s just that I’ve hit a bit of a roadblock. The code is 100% open source GPL3, so you’re free to modify it however you wish. All the source code comes with the addon. The code I’m working on has a some improvements on usability and normals, but is not currently fully functional. So if you choose to make patches, there might be some overlap on what gets done, when I’m finally able to release it.

Also I have a priority list from this thread of possible improvements (in order from most important to least important):

  • Cache for objects (remember STEP file, then ask if reimport on .blend reopen)
  • Without closing, update STEP file when it’s changed
  • Bug: some files create only empty collections
  • Import multiple STEP files
  • Apply scale
  • Sanity limits for deflection values (min and max)
  • Change filename.flat and filename.hierarchy as options
  • Meshing improvements
  • Save preset
  • Automatic UV generation
  • Programmatic invocation of the import operation

You can comment on what you find most important.


Sounds great that development is still going on. Priority list looks good and I don’t think it makes much difference to shuffle individual items.

‘x86_64|Darwin-19.6.0-x86_64-i386-64bit|3.7.4|Clang 11.0.0 (clang-1100.0.33.8)|2.83.3|/Applications/’

After I installed your free addon and tried to convert STEP to glTF/glb, the software crashed.
I couldn’t attach the log as I’m a new user but, I’ve put the log here:

As the Gumroad description states, the addon currently supports only Windows.

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Hey you can also use

I personally also own a copy of MOI which is the best CAD to OBJ mesher in the universe.

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I was so excited about your script, that I got the STEPER on Gumroad. Unfortunately I also work on a Mac system. Is there any plans to make the addon available for MAC as well?

There’s a mountain of work to be done before I can even consider such a thing, so unfortunately I can’t give you any promise or estimate.