Moving/rotating objects Symmetrical ly in a block

[ross.mclee]

Hi,

I am getting more familiar with symmetrical constraints within dynamic blocks, but wondered...

From what I  can see - Symmetric constraints work on individual lines and arcs, so you have to select line 1, then line 2 and then a symmetry line. For polylines you need to select each individual segment.

Is it possible to move/rotate lots of geometry in one go and have a mirror image of the same geometry move/rotate symmetrically across a symmetry line. E.g. What if you have 100 lines and arcs that make up the object you want to mirror. Do you have to select each individual element or can you select it as a group or an embedded block and state the line of symmetry? The latter would be ideal as you can modify that block and redefine it as often as you like.

The attached example shows how I have done it selecting each of the 17 individual elements of a mounting bracket for a TV soundbar. The brackets come in two separate halves and would be installed in a symmetrical fashion.

The second bit is the same but the geometry for one half of the bracket is saved as a block which is mirrored. I notice that the move and rotation isn't perfect - needs fixing!

Any thoughts ideas welcome.]

TIA

R

[j.palmeL29YX]

First:

Mixing constraints in with dynamic parameters/actions (as you did) usually just causes problems. I'd strongly recommend to avoid that.

Second: 

You're right, to apply symmetrical constraints to a complex geometry can be a pain (and will lead to nightmares). 

And additional: In your left-hand example, a large number of additional constraints are required to obtain a stable geometry. For these reasons I would strongly prefer the right version (2 blocks).

Third: 

Attached and example how to move the block symmetrical. 

Unfortunately I don't understand which geometry you want to rotate about which point. If you can show  us an example how the block should look after rortating I will complete (and if you need explain) my suggestion.

[ross.mclee]

Thanks @j.palmeL29YX 

I agree mixing the parameters and constraints is normally a no no and I am already running into problems.

I can do a move/stretch as you show with linear parameters moving each half in opposite direction (using a mid point parameter for example)

The move/stretch is also accompanied by some sort of rotate of each half and that's where the symmetry element came in. I wondered if there was a way of rotating the other half of the mount by the same number of degrees but in the opposite direction but with the other half having it's own rotational point.

Not wanting to complicate my original question too much, but the idea is that the slots have a bolt passing through them which are inserted into the back of an LCD's standard VESA mount holes say 100,200,300,400, 600 mm apart.

I've attached and example of what I am trying to achieve. There are potentially lots of rotational points running along the centreline of each slot. There are larger brackets than this one so to fit a 65"...75" or even an 98" LCD, I'm just using this as an example, hense, being able to swap out the basic geometry for the various blocks of different sizes would be ideal.

Having typed, that I wonder if the constraint should be that the centreline of the slots remains a fixed vertical distance (say 300mm) and any moves/rotations would be constrained by that?... My brain is starting to hurt !

[Libbya]

I wouldn't use any constraints for that block.  Symmetrical rotation (and stretching) can be done using only dynamic parameters/actions.

[j.palmeL29YX · Accepted solution]

Attached a new "Main" block to demonstrate (as example) how you can slide the both soundbar brackets along the 4 bolts symmetrical. Drag the grip a little up and down an see what happens. (BTW: here the movement doesn't stop when the end of the slot is reached). 

But: 

To apply this principle to your project, your block would have to be completely rebuilt structurally. (e.g. because it is not possible to use further dynamic sub-blocks within a dynamic block and to use their functionality).
With the complexity of your project I am afraid that the possibilities of AutoCAD are not sufficient to realice that. 

[ross.mclee]

That is a great way of doing it... Thank you.
R