Rotated Origin

Hi Bernd bbguenthe ,

As for point 2: Do not Apply the Rotation of your Objects, if you can avoid it! (Now you must suffer.) Luckily it's a 'cube':

Switch to Edit Mode, Select 1 Face and make a Custom Transform Orientation, by clicking the '+'

Then switch to Object Mode, go to Options > Transforms > Affect Only > Origins. Now you can Align the Origin to your Custom Orientation:

Don't forget to disable the Option (> Origins).

You now have the Object's Rotation back (apart from possible multiples of 90°, depending on which Face you Selected in the first step)):

As for point 1.: Not sure if this is easier for you, but you can use Set Cursor and set the Projection to Geometry. Then place the 3D Cursor on the Face you want. Add an other Object (I mostly use an Empty for this kind of thing) and set that to Align to the 3D Cursor.:

Then Parent tne Object to the Empty and you can Snap the Empty to any Surface you want (with Align Rotation to Target enabled). (Again, similar to above, you might need to Rotate 180°, because the Z is facing the wrong direction).

There are Addons that make your life easier, when you need to do this a lot, but it's still good to know some manual ways.

You can of course also simply cut the door out of the wall in Edit Mode. That is how you usually make doors and windows in walls.

But I still wanted to show you some align tricks.

Wasn't there a copy transform addon that came with Blender with all sorts of great copy options? I can't seem to find it now, was it killed? 

Hi Bernd bbguenthe

Looks like Martin already got you covered for the origin orientation. I totally agree with not applying rotations, except for specific reasons (array cutter objects sometimes, set new default rotation). At least with Martin's steps you can get it back.

I usually find the snapping with align rotation to target somewhat unhandy, because of above steps. It always seems to require some extra objects and additional rotation afterwards, with, as you pointed out, the z orientation and normal directions. Sometimes it's unavoidable though and Martin already gave you a good way with the empty.

For your specific case with the door along a slanted wall I wouldn't use align rotation to target at all. Here's how I would go about it with precision:
1. On your wall select 3 vertices along the angle (blue circles)
2. Fire up MeasureIt, click "show" and with the vertices selected click on "Angle". This will give you the precise angle of your wall. You can adjust the precision in the tool.

3. In Object Mode select your door. Since it already stands at 90 degrees to the wall in this case, it only needs to be rotated by the difference.
    So R->Z->46.41038

4. Your door now has the correct same rotation as the slanted wall. If you did this in object mode, your local rotation will be correct and you can move and snap it regularly.

Alternatively you can also for example press g->y->y to move it along its local y axis without changing the general transformation in the header.

Another tip: If you model the door yourself, I personally prefer to model it first aligned with the global axis and then rotate it in place. Can make things easier for certain operations.

Hope this helps with your situation. :)

Omar Are you thinking about the "Copy Global Transform" addon?

No, it was an old addon that replaced the Control + C command and it gave you tons of copy options. Super useful. You guys don't remember it? 

That's the Copy Attributes Addon. Still exists.

Yeah that's the one. It has all sorts of easy transforms copying, I found it super useful. 

Hi Bernd,

Thanks a lot for your kind words!

I actually don't use a lot of Addons, but I do have Hardops and Boxcutter and they are fantastic, (and have life-long support and updates, so worth the money), but I'm not sure they'll help with these specific problems.... I also hear great things about MeshMachine from someone whose opinion I trust (and who knows a lot about Addons from using them and writing them),

Hi Bernd,

It's math I can do, so anyone can do it 🤣
As always in Blender there are many ways that lead to a result. At least now you have lots of options.

Btw. there are certain situations, where applying the rotation makes sense. I do this twice during the course I believe, but also explain why in that situation.
Under normal circumstances though mostly not the rotation and pretty much never ever the location. :)

Omar The "copy attributes menu" addon gets a specific mention in the beginning of the course. 😉

There you go Bernd, the addon from the beginning was right under our noses the whole time. An addon so useful it has been there from time immemorial, like a plate or a spoon, those designs are so good, they've never been updated.