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gumyr / build123d

A python CAD programming library
Apache License 2.0
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Compound export_step doesn't keep its child's positions #301

Open longhan opened 1 year ago

longhan commented 1 year ago

When create a compound name 'assembly' by add its children (also a compose, by using import_step), then using joins to relocates the children.

the ocp_vscode viewer showed the root compound perfectly with its children being relocated. IMAGE 2023-08-17 13:04:01

But when I use the assembly.export_step(path) and using Freecad to import. All the children locations is the same to the assembly before relocated. IMAGE 2023-08-17 13:04:07

gumyr commented 1 year ago

This one is going to be difficult to fix as I don't know how to reproduce it. Here is the latch and slide (from https://build123d.readthedocs.io/en/latest/joints.html#linear-joint) exported as an Compound/assembly to a step file and imported to FreeCAD: image

Is there anything else you could share to help narrow down the problem?

Gigahawk commented 1 year ago

From discussions on discord, this may have something to do with the way OCCT is used to import step files. Below is the sample STEP file that demonstrates the issue: reprapdiscount_smart_controller.zip

This file was generated by this GitHub Action, which uses https://github.com/Gigahawk/freecad-export-action to export the KiCad design as a STEP file through KiCadStepUp

When importing this file in build123d, there is an extra set of solids placed at Location((0, 0, 0), (0, 0, 0)) (screenshot shows cq-editor, but the same behavior is seen in ocp-vscode) image

Working examples

When this file is opened with CAD Assistant, it looks fine image

It also looks fine in the latest version of Mayo (0.7.0) (the extra solids are named SolidXXX in the tree, enabling/disabling them doesn't do anything) image

It also seems to be fine in FreeCAD 0.20.2 (I have not found any set of import settings that causes it to break) image

Broken examples

In the previous Mayo release (0.6.0), the extra solids are shown: image

They are also shown in Fusion: image

Misc

In Mayo 0.7.0, enabling/disabling the extra solids seems to have no effect image

In CAD Assistant, changing the transparency on one of the extra solids changes the transparency of the corresponding solid in the correct object: image Deleting the solid doesn't delete anything in the correct object, but the transparency change stays: image

Similarly, in Mayo 0.6.0 enabling/disabling the extra solid is linked only to the extra solid: image

In build123d, this behaviour can be (ab)used to generate the correct output

# HACK: import_step randomly places extra solids at origin?
pcb = Compound.make_compound([s for s in pcb.solids() if s.location != Location((0, 0, 0), (0, 0, 0))])