Improvements on corner milling

[Salamandar]

The two commits are independent.

The first one disables milling on where it's not needed. On the screenshot, you can see the milling on the blue corner, and we don't want that.

The second commit changes the dogbone profile. Instead of going far into the part, we can just move at 45° inside the corner.
Here it's the "less extreme dogbone" : http://fablab.ruc.dk/content/images/2017/03/dogbones.jpg

[Salamandar]

The first commit can be a "drop-in", but the second should be user-configurable (which profile, and which "depth").

[bmsleight]

Looks great - thanks for the pull request.
Work busy at the moment will try to look at weekend.
Kick-me if I not replied by Nov.
Cheers. Brendan

[Salamandar]

Looks great - thanks for the pull request.
Work busy at the moment will try to look at weekend.
Kick-me if I not replied by Nov.
Cheers. Brendan

No problem.

I force-pushed the last commit as it was missing a line (the definition of delta).

[samowitsch]

Hi @Salamandar. I have looked at your changes and at one place the dogbone is missing.

[Salamandar]

OK. I think I know what's the issue. I'll check it out.

[Salamandar]

Yeah, I see what's going on. I disabled bits on angles. The problem is that, without this "safeguard", the angles are broken. See the screenshot.

[Salamandar]

I guess a workaround would be to re-add some materials at those places, but meh.

BTW, there would be a HUGE performance bump if you only used 2d primitives (then extruded).