Possible BUG: Unit and Value Display in Preferences also seems to affect accuracy of constructing geometry

[tehatinrichst]

Description of the problem

So, I followed a tutorial on Youtube (https://www.youtube.com/watch?v=hkMfm5SXSNE&t=5s) where starting at 16:53 an offset plane is created to mirror the half of a ball. Then this copy is rotated 36 degrees to match up with the bottom part and then the combine fails.

Solving the problem

I found out, that this can be fixed, by simply setting the General Precision property in the Unit and Value Display in Preferences to 0.1234 or above. If it is set to 0.123, the offset plane is created at a distance of 116.372 mm, but if you change the General Precision to 0.1234 and create the offset plane, it is created at a distance of 116.3719 and the combine works!

The reason I think this is a bug

I would not expect, that a property in the Unit and Value Display section would also affect rounding off values in constructing geometry. I would propose a change that the General Precision property and all other Unit and Value Display section properties are not used for rounding off. They should only be used for the exact purpose of displaying values, so only rounding off for formatting.

[jhackney1972]

I have to take issue with your claim that the Unit Precision, set in the Preferences, has any effect on the distance you set between two work planes.  Take a look at the Screencast where I proved this to be true.  If I am not understanding your BUG claim, then please clear it up for me.

[tehatinrichst]

EDITED (replied to myself, cant delete the message)

[tehatinrichst]

Thank you for responding!
I understand what you are trying to show to me, that in fact the General Precision is simply used for displaying purposes and indeed, that holds true when you type in the values yourself.

The problem I am having here in case is that when creating an offset plane and selecting another piece of construction geometry (such as a point, or a plane) for determining the distance, the values are rounded off.

I have a very simple example to reproduce exact this behavior:

1. Set the General Precision to 0.12345
2. Create an offset plane, using the XY plane for example as a reference and type 1.12345 as a distance
3. Change the General Precision to 0.1
4. Create an offset plane, using the same plane you selected initially in step 2 (the XY plane in that case) and as a distance value, don't type a value, but click on the plane you created in step 2. This will round off the value to the 0.1 precision (so that would be 1.1) and that is automatically typed into the distance field.
5. Measure the distance between plane created in step 2 and 4 and the result should be 0, but it is of course 0.02345

So the problem is that Fusion 360 rounds the value off to the precision selected in the General Precision property and of course it makes sense, that you also see that rounded off value in the Distance text-field when constructing an offset plane. What does not make sense though is that when you select a more precise reference item for determining the distance (such as the XY plane and the new plane in this case), that the rounded off value is used as the new distance. The program should use the calculated distance between the two references and maybe instead of showing a rounded off value, it should display something like fx:Plane1-XY

Hope this smaller examples makes it better to understand.

[jhackney1972]

Thanks for the example to try.  I can confirm that I am seeing the same issue that you describe.  @jeff_strater could you take a look at this and let us know your feelings?