Tuesday, 27 December 2016

Fun with FreeCAD

On to the FreeCAD tutorials, starting with something basic, and taking notes.

Having auto-constraints on is rather nice. However, it can lead to oddities - at the 26mm length constraint, my design flipped out and only became orderly once I deleted the coinciding constraints and then added them back with Undo. Wut?

Scrollbars within scrollbars don't work well on Mac at all. Also, the Macbook Air has a delete button, but not backspace, so deleting items is tricky. But aha! You can use Fn-Delete to delete. And, as soon as I delete one of the lines in the tutorial object this way, FreeCAD crashes. Delightful.

"Now in the Combo View, click on the OK button" - yeah, well, there isn't one. ITYM "Close".

Non-dialog panels that have an OK button is one thing - having several that differ between "Ok" and "Close" is annoying - but it gets really confusing when you can make all manner of other changes in the meanwhile. OTOH, I don't like modal dialogs.

Ah, joy. Random "Overconstrained" errors. For some reason my sketch is rotated 90 degrees compared to the normal axis, so trying to set horizontal length on something that looks horizontal gives a conflict with the verticality constraint. This program could do with better error messages for some common constraint conflicts, e.g. "A vertical line cannot have a horizontal length". But why it's rotated I do not know, the axes look just fine. I tried reconstructing the initial model in a few different ways, but it always switches to XZ plane when adding a sketch on the back.

Curious. The "Angle" property of the sketch is 240 degrees, but degrees of what? 240 is the XZ plane, 120 is the YZ plane, and 0 is the XY plane. I still don't see the property that defines which way is up. Regardless of Axis properties, the coordinates are clearly (y,x) format. Bizarre.

The next picture does indeed show the element standing on end, there's just no explanation of why this happens. Nor is there an explanation of things like having to press 'Esc' to get out of a given tool. Maybe that's in the very beginners intro.

I like that the view buttons cause a little animation, makes it easier to understand. In OpenSCAD, clicking one just snaps to that view, which in some cases is indistinguishable from other views.

I like how the tutorial starts out by saying it's using Auto Refine, but that they recommend not doing that. Do as we say, not as we do. So now my sketch looks different, hopefully it won't behave differently.

External geometry selection requires holding Cmd, but internal selection doesn't. Confusing? Slightly. Mentioned in the tutorial? Nah.

I am amused by the final step: Call out to OpenSCAD to get rid of the extra lines.

For my Macbook, the Touchpad navigation is pretty nice once I get used to it, especially the click-less panning. There's just something odd about exactly when the Shift press is registered, probably related to what happens to have focus. Using just Shift and Alt, I can avoid clicking entirely to change my view.

I'll have to try designing a few "real" things, but it does look like there are objects more easily defined in FreeCAD than in OpenSCAD - things where constrained relations are the defining features in particular.

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