How to intersect and have the cut geometry as groups?

kwistenbiebel

Hi all,

It's something that bothers me since long time.
sometimes when trying to cut an organic form in half by intersecting it with e.g a plane, selecting the geometry by hand is a tedious job.

I would love it if the interesection would automatically generate groups.
(for instance two halves of an apple as seperate groups).

Is this possible in some way? Maybe some ruby exists for it?

Thanks in advance, your help is appreciated.

Regards,
Kwistenbiebel

jeff hammond

yeah, i've asked for this one before as well but to no avail.. my situation usually involves deleting one half after the intersection but i'm sure you could apply some of this to other operations..

one thing TIG did for me a little while ago was to update his invertselection.rb which allows you to select only the faces you want to keep and delete everything else.. this works very good in certain cases but if you're dealing with a lot of faces that you want to keep, it would still be tedious..

in those cases, i like to orient my drawing so that i can only see the edge of my cutting plane with the half i'd like to keep on one side and the stuff to delete on the other.. i'll then use the selection tool window to select everything i want to erase and then hit delete... the trick is to drag the window from Right TO Left instead of l to r... doing this will select a line or face even if it's not entirely encompassed by the window.. you might have a little bit left to clean up afterwards but this technique will get rid of the bulk very quickly..

still, i'd much prefer the intersect then group method.. painless..

Dave R

I frequently cut components in half but they are symmetrical so I make the remaining half a component, copy it, mirror it and so on. I am imagining in your case that the halves would not be symmetrical. My inclination would be to get through the Intersect stage and then make a copy of the apple. Then delete the unwanted half of each copy. I find switching to parallel projecting and a view that shows the cutting planes on edge works best. I use a right to left selection box around the geometry I want to delete but stay clear of the cutting plane.

A plugin that could do this automatically would be nice but until sucha critter exists, I think this works well enough.

Hope that's helpful.

dave

kwistenbiebel

Thanks Jeff for that reply.
I share the exact same need.

It should be great if Whaat would incorporate a function like that for the 'organic modeling' module he is elaborating.

Thanks by the way for that 'right to left' selection method. I didn't know that and it sounds quite useful.

Cheers,
Kwistenbiebel

kwistenbiebel

@dave r said:

I find switching to parallel projecting and a view that shows the cutting planes on edge works best.
dave

Another good tip when modeling symmetrical things.
The automatical grouping thing would still be handy for all other forms though.

Thanks for the reply. appreciated.

Dave R

Actually, your idea of automatic cutting and grouping could be very handy for symmetrical things. I imagine a plugin that has an option such as Divide Along>Red Axis, Green Axis, Blue Axis. After making the choice the script looks to find the centerline, deletes one half of the geometry, hides the seam line edges, makes a component, copies it, mirrors the copy and places it next to the first half. I would imagine you could get some rather unpredictable results from trying to run it on assymmetrical components.

kwistenbiebel

can be useful...but I have no need for automatic copying of the symmetrical half.

I popped the question on having groups when intersecting just as a means to be able to select certain parts of geometry of a organic form.

Gaieus

Moved to the SU forum.