How to get STL as bytes from a cadquery.Workplane without writing them to a file?

Jaakko

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Dec 18, 2021, 12:22:18 PM12/18/21

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Hello all!

I am making a web application (with Svelte front and Django back) and I am trying to implement following functionality:

User inputs measurements, client sends them to the server and server runs cadquery script and returns an STL file to the client where it can be previewed in browser and saved to users computer.

Does anyone know how can generate the STL file bytes from the cadquery Workplane without writing them to a file?

Thank you in advance

Jaakko

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Dec 19, 2021, 6:17:52 AM12/19/21

to CadQuery

Also if anyone has any ideas or suggestions of an efficient way of transmitting the 3D data from cadquery running in the server to the client I would be interested to hear!

Lorenz

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Dec 19, 2021, 11:05:34 AM12/19/21

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Hi Jaako,

> how can generate the STL file bytes from the cadquery Workplane without writing them to a file?

Export with exportType STL uses OCP.StlAPI.StlAPI_Writer. The StlAPI_Writer expects a string argument for filename so I don't see an easy way to avoid this without writing a temp file.

The AMF exportType also currently writes to file but with some minor Python code changes to the AmfWriter you could support writing to IO stream.

Regarding display in the browser, I would suggest to take a look at jupyter_tools.py. Disclaimer - I have not build such an app. My advice is based on using cadquery with jupyter lab. As a jupyter lab user I know that cadquery natively supports display in the browser. I think the HTML docs use the same (VTK) method for display in the browser as well (see cq_directive.py).

Lorenz

Roger Maitland

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Dec 19, 2021, 3:31:47 PM12/19/21

to Lorenz, CadQuery

Hi Jaakko,

CadHub sounds very similar to what you're trying to do - you might want to look at their code to see how they do it: https://github.com/Irev-Dev/cadhub

Cheers,

Roger

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Jaakko

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Dec 22, 2021, 12:57:37 PM12/22/21

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Thank you for the advice,

I ended up just writing the stl to temporary file.

I used StlAPI().Write_s(shape, filename, False) method for writing the stl because it writes the STL in binary format

and used

tempfile.NamedTemporaryFile() to create the temporary file.
In the front end I use ThreeJS library for displaying the 3D-model. 

Jeremy Wright

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Dec 27, 2021, 2:37:03 PM12/27/21

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The CadHub integration of CadQuery uses cq-cli, which allows the output of the STL text to the stdout stream.