Fusion 360 and SVG issues. Possible Bug

[celticone]

I have been having quite a few issues the last few months with Fusion 360 importing SVG designs. Mainly when I am using an SVG imported in Sheet Metal mode to extrude or to cut a body. This is the only time I have to scale an SVG object to fit a face.

Many of the profile import issues are due to scaling a design in Inkscape. After investigating this at both the Inkscape and Autodesk forums, I am not sure what the true issue is. Wild guess on my part is that it is accumulated rounding errors in Inkscape and the way Fusion 360 processes SVG files.

Included a zip file with several SVG and Fusion files with a txt file explaining the issue in detail. 

[g-andresen]

Hi,

I recommend you import the SVG at its original size and extrude it.
Then scale the body and project the profile into a sketch if needed.
Scaling SVG can cause vectors to "break" and warp. Also, vectors in SVG are overlaid in some places.
Fusion then "probably" has trouble identifying which vectors to connect.
However, in pure graphics programs like Inkscape or AI this does not matter.

günther

[celticone]

Replied to myself! LOL

[celticone]

You used the good profiles in the video. Not the profiles that are bad. 

I used that same  technique of projecting the bad profiles onto an new sketch about a week ago hoping it would solve the issue. Nope

The info in bugs.txt explained how I fixed the issue that actually revealed how complicated the bug is. It's not just a SVG scaling/transform issue. 

Thanks

[g-andresen]

Hi,

1. Were the bad profiles scaled in Inkscape?

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@celticone  schrieb:

I used that same  technique of projecting the bad profiles onto an new sketch about a week ago hoping it would solve the issue. Nope
2. To do this, you must first repair the bad profiles.

günther

[celticone]

Correct. 

All the paths were scaled 10,000% to bring out the accumulated rounding errors that are inherit in SVGs. What I found amazing is the paths that were not aligned in inkscape produced a good profile. Wasn't expecting that. That is why I questioned why path 477 of the aligned paths came out with a valid profile.

When I simply moved that path to the bottom of the xml stack in Experiment 4 it was no longer a valid profile but 2 other profiles became valid that were not valid in the other experiments. 

Yes - accumulated rounding errors in SVGs cause problems but it is the way that Fusion 360 is translating paths into valid profiles that is causing the real issue. Is it a bug? No - more an algo issue. That is why I am not expecting a quick hot fix to this. 

Right now I am writing a tutorial to solve such issues for my users. There are quite few different approaches that I use and a user may have to try multiple methods. It is a pain  but it is what is. 

Thanks for responding

[celticone]

...

2. To do this, you must first repair the bad profiles.

....

Fixing them in Inkscape by nudging the nodes to the grid and realigning the paths to the grid as I did in experiment 3 and 4 is far easier than trying to repair a bad profile using Fusion 360. Been there - done that quite a few times since June. Its not a fun process.

Thanks for the response

[g-andresen]

Hi,

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@celticone  schrieb:

...Its not a fun process.

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Probably true!

I'll repeat myself and say that you should never scale SVG outlines before exporting them.
But it should also be noted that when you export SVG, you can't assume that it will be error-free. This is due to the format.

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@celticone  schrieb:

Fixing them in Inkscape by nudging the nodes to the grid and realigning the paths to the grid as I did in experiment 3 and 4 is far easier than trying to repair a bad profile using Fusion 360. 

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But does not prevent new problems from occurring during export!

günther

[celticone]

...

I'll repeat myself and say that you should never scale SVG outlines before exporting them.

....

Correct. That is why I tell my users to avoid that if possible. Bring the original SVG design in. Complete the design in Fusion and let Fusion 360 do the scaling. 

However - in sheet metal mode you really have no choice because Fusion  scaling doesn't allow actual dimensional scaling that you have in Inkscape. You cannot scale by 3mm in the horizontal or -2 mm in the vertical to fit an unrolled sheet metal design. 

If I could do that type of scaling - the problem would  be solved 100%. Maybe.

...

But does not prevent new problems from occurring during export!

...

Yes- it solved the problem. It imported perfect. Experiment 3
The issue is that it shouldn't have been an issue to begin with. Technically not a bug but an algo issue. 

Some finished examples: https://grabcad.com/library/celtic-knotwork-bracelet-1

I have come up with several different methods to force the design and I am currently creating a tutorial on the methods. Sometimes they work. Sometimes they don't.