Mirror and Symmetry

Hi All,

the Mirror and Symmetry commands
they cannot be tied to a straight line
updating each time to it?

Mirror creates a mirrored copy of geometry each time it is executed.

Symmetry creates and then updates a mirrored copy of the geometry. The relation between the copies is controlled by the Continuity= option in the command. If Continuity=Smooth is selected then the input line/curve will be modified so that it and the mirrored copy will have G2 continuity. If a straight line is used as input then the line will be rotated perpendicular to the mirror plane. Use Continuity=None or Continuity=Position with lines.

Hi David.
thanks for answer
attach to the straight line I meant:
if I move the line, the mirror or symmetry changes angle

Hello - if you use Symmetry on a line, with Continuity =Smooth you should get two co-linear lines; with History on, rotating the lines should just snap back to co-linear. Not sure what that means in your overall question…


Hi, Pascal

the final one is the right result
to be obtained automatically.

No sorry, the mirror axis is not history enabled in either the Mirror or Symmetry commands. Only the original curves can be edited and update with history, not the axis.

The same is true of commands like Revolve - the revolve axis is not included in the history.

The main reason is that, despite the fact that you drew a line object as a mirror axis, that line is not really used - the axis is actually determined by the two picked points, which are not “real” objects in Rhino. History is currently object based - i.e. modifying a “Parent” object causes the “child object(s)” to update. As there are no Rhino objects to edit for the axis, it is therefore not able to be accessed to be history-modified.

I know this has been asked for in the past for a number of history enabled commands which use pick point inputs to determine an axis or other parameter.


Hi, Helvetosaur

this I had already understood.

so is it not possible to tie the symmetry axis to the two points of the line?

No, not currently.

Ok Thanks Helvetosaur