topic Re: Imported .step bodies move in different directions. in Fusion Support Forum

Imported .step bodies move in different directions.

Dylan.evansEJABQ — Wed, 14 Dec 2022 09:44:09 GMT

So really I just want to understand and resolve the issue I have in the screen recording attached. I am just an amateur/casual user, so bare with me if I am missing something simple.

In short - whenever I import a .step file (In the example it is a fully modelled case for something I am making) and then attempt to move the bodies together - many of them move in entirely the opposite direction or at entirely different ratios, so all the parts end up all over the place.

This never happens on a model I have created myself.

So try to just move the components? - Sure this does work at first, but I actually want to split the model and then join the two halves. This means there are two different bodies in one component group and can't be moved individually (I think)

I have also tried moving all the individual bodies to one group. But this crashes Fusion without fail, so thats a no go.

I can think of other ways to approach this. (maybe split the model, delete one half and mirror...) but I would like to understand why this happens, and if there is a way to 'reset' all of the individual bodies to have the same reference when it comes to a move. Seems like a simple thing!

Re: Imported .step bodies move in different directions.

sutherland- — Wed, 14 Dec 2022 10:36:56 GMT

Hi @Dylan.evansEJABQ

Try moving components instead of bodies.

See the gif attached:

Re: Imported .step bodies move in different directions.

Dylan.evansEJABQ — Wed, 14 Dec 2022 10:41:25 GMT

Yes I did try this (mentioned in first post) but this doesn't work after splitting one of the bodies - I think this is because there are then two bodies in one component I wish to move independently of one another.

Is there not a way to fix the root cause of this, as opposed to finding other solutions to the problem?

Re: Imported .step bodies move in different directions.

Dylan.evansEJABQ — Wed, 14 Dec 2022 11:03:48 GMT

Without fixing the root cause, it seems to have the effect of breaking everything I try to do.

Here I try to mirror the body after splitting, but no luck (something to do with bodies in hundreds of different components?) I then show that as this selection of components is now split, I can no longer move one half independent of the other. If I attempt to move one half to a new group, fusion 360 will crash.

Although it doesn't solve the root cause I have just realised I can copy and paste into a new component. This does seem to reset whatever is going on and seems like a solution for now. I would still like to understand why the object all move differently - is it a bug/quirk? Or expected behaviour because of a certain setting?

Re: Imported .step bodies move in different directions.

dsouzasujay — Wed, 14 Dec 2022 11:04:10 GMT

Hi @Dylan.evansEJABQ

Could you please share the file, looks like data specific issue.

Re: Imported .step bodies move in different directions.

sutherland- — Wed, 14 Dec 2022 11:40:19 GMT

Sorry, misunderstood the second part of the original post.

I agree with @dsouzasujay

It would be useful to have the model, so we can experiment with the case-specific issue you are facing.

Re: Imported .step bodies move in different directions.

Dylan.evansEJABQ — Wed, 14 Dec 2022 11:54:40 GMT

Unfortunately it's behind an NDA, but it is something i have experience with other files I think are public. I will have a quick look.

Re: Imported .step bodies move in different directions.

Dylan.evansEJABQ — Wed, 14 Dec 2022 12:01:52 GMT

Attached is an other download that exhibits the same problem (these are both from Chinese vendors - not sure if there is a specific CAD application they are using that this is common to)

If you open the first file in the zip and attempt to rotate it, then several of the screws will rotate on a different axis and detach from their place.

Re: Imported .step bodies move in different directions.

dsouzasujay — Wed, 14 Dec 2022 12:27:19 GMT

Hi @Dylan.evansEJABQ

The file in zip files are related to drawings.

If it is sensitive, feel free to send it directly to me (Sujay<dot>dsouza<at>autodesk<dot>com)

Re: Imported .step bodies move in different directions.

Dylan.evansEJABQ — Wed, 14 Dec 2022 12:29:48 GMT

Whoops wrong zip

(I do not suppose the files are particularly sensitive to be honest... the Chinese manufacturers are pretty competent at copying each other regardless of NDAs - but the zip in the attachment shows the same problem)

Re: Imported .step bodies move in different directions.

dsouzasujay — Wed, 14 Dec 2022 12:52:26 GMT

Hi @Dylan.evansEJABQ

I'm able to move all the components and bodies by selecting "Components" from the browser as mentioned by @sutherland-

Re: Imported .step bodies move in different directions.

Dylan.evansEJABQ — Wed, 14 Dec 2022 12:56:18 GMT

Yes, this is mentioned a couple of time above, but I go on to explain that this is not a solution and doesn't work if one of the components has two bodies you want to move independently. I have in fact found a solution to the problem: if you copy and paste all bodies into a new component it solves the problem as it stands.

I was intrigued to know why this was happening. But if the answer is that it is just a quirk of the imported .step and there is no real direct answer to this question then thats fine - the problem it has caused is solved.

Re: Imported .step bodies move in different directions.

jeff_strater — Wed, 14 Dec 2022 22:30:25 GMT

@Dylan.evansEJABQ - you are correct that this is incorrect behavior. Thanks for sharing those STEP models. My guess is that those bodies in the STEP files have some kind of transform on them that Fusion is not expecting (possibly a mirror transform), which is causing the unexpected Move Body behavior. I will create a Fusion bug to track this.

On second thought, I'm no longer sure that this is wrong - I'll be back later to explain why...

Re: Imported .step bodies move in different directions.

jeff_strater — Thu, 15 Dec 2022 00:00:08 GMT

Here is what I think is at the root of the behavior you are seeing, and it is expected. In the screencast, you will see that I create a new instance of a component, and rotate and translate that component by some amount. If I then use Move Body, you can see that the body move is applied differently to each instance. I believe that is because Body Move moves a body within the owning component's transform, relative to that component's origin. I think there is also an effect caused by Body Move, because if you move a body within its component, it will apply to all instances. So, while dragging, you are actually moving the same body more than once - once within each instance.

screencast: https://knowledge.autodesk.com/community/screencast/74352712-8396-4a09-a756-9d41a77696f8

Re: Imported .step bodies move in different directions.

Dylan.evansEJABQ — Thu, 15 Dec 2022 11:07:22 GMT

Hi Jeff,

Thank you for your insight, that makes a lot of sense when thought about in this way - and explains why copying all bodies into a single component eliminates the issue.

Would you be at all interested in replicating the crash I experience? It is when selecting all bodies of many components and then right clicking and selecting "move to group" then selecting a group in a new component. For me this causes a repeatable crash, although a copy-paste does not.

I did submit the crash report, so if it wouldn't be of interest then no problem, and thank you again for your explanation.