Chop off end of group

jhearcht · 17 Oct 2008, 15:35

I have created a fairly complex double-ended double-pitch roof with angled overhanging gable ends. Now I want to use that same roof on another part of the building. In that location one end of the roof abuts the wall of another part of the building. Now all I have to do is chop off one end of the roof group, and voila, a single-end roof.

I have tried <<intersect with model>> but that seems to inadvertently delete some walls in the model perpendicular to the cutting plane. So I created a new face and placed it in alignment with the wall of the model. When I right click and <intersect with selected>> a new line is drawn around the outside of the roof group. But it doesn't cut any of the surfaces inside the group.

Chopping off one end of a group sounds simple in theory, but it's not working out in practice. It would be nice if I could use the <<section tool>> to carve the object, and make the chopped-off part disappear.

Is there a Plug-In tool to do this job. Or will I have to do it the hard way: surface by surface and line by line? Any suggestions will be appreciated.

remus · 17 Oct 2008, 15:57

Youre right, it is a bit fiddly, but their is a workaround.

If you select the face you were using as a cutting plane->ctrl+x then open up the group edit->paste in place, select everything in the group->right click->intersect with selected. Its then just a case of tidying up all the remaining stuff.

Jean Lemire · 17 Oct 2008, 16:16

Hi Jhearcht , hi folks.

Can you post the model or at least the relevant part showing the roof and the spot where you would like to import it.

Just ideas.

Gaieus · 18 Oct 2008, 04:07

Hi Jhearcht,

What you experience is the normal and logical way SU works; intersection lines are always created within the context you are in. So by entering the group's editing context (double click to edit) and performing the intersection there like Remus says, will do the job.

jhearcht · 20 Oct 2008, 16:50

I did successfully chop off one end of the roof by ungrouping before intersecting. But it was a tedious process, and I was left with the quandary of how to regroup the roof without selecting other extraneous items. I solved that problem by using MOVE to relocate the roof temporarily while I created an intersecting plane. After cleanup, I just moved the roof back into the original location.

Later I discovered the EDIT GROUP item in the context menu. That will make it easy to edit within the group without having to reselect the pieces. But what I was originally trying to do was use the INTERSECT command to cause objects inside one group to intersect with another group. Is that possible?

My inexperience usually results in doing things the hard way.

Gaieus · 21 Oct 2008, 10:33

You mean that the intersection would apply to BOTH groups?
That's not possible. One group can be intersected by being edited but you cannot edit two groups at the same time.

sorgesu · 21 Oct 2008, 11:40

You can use the section tool to create a cut. Place the section plane where you want to have your cut insdide the group. So you are editing the group, yes? Then right click on the plane and from the context menu click on "create group from slice". this will create vector lines where the section cut is. You can get rid of your section plane now by deleting it. Then select the grouped vector lines created by this action and "explode" them. You now have your cut lines in position.

jhearcht · 21 Oct 2008, 18:00

@sorgesu said:

You can use the section tool to create a cut. Place the section plane where you want to have your cut insdide the group. So you are editing the group, yes? Then right click on the plane and from the context menu click on "create group from slice". this will create vector lines where the section cut is. You can get rid of your section plane now by deleting it. Then select the grouped vector lines created by this action and "explode" them. You now have your cut lines in position.

This is exactly what I was trying to do. I was not aware of the "create group from slice command", but I thought the Section Tool should be able to do something like that. Thanks very much for the help. I'll try to remember it next time I need to chop off part of a group.

jhearcht · 23 Oct 2008, 21:49

I have tried the <<create group from slice>> command. Now see it doesn't really do what I want to do. It does draw a line around the group, but it doesn't actually cut anything, even if the group if exploded. I still have to go in to select and remove the unwanted parts, line by line, and face by face, with lots of zooming and rotating. Surely there is a tool or command to simply chop off one end of a multi-part group. I need to do this operation several times, and it will take several hours at this rate. In my CAD application I can use a line or a surface to chop off part of a group---quick and simple.

Gaieus · 23 Oct 2008, 21:58

In SU you can also use a simple plane to chop off part of your group (make sure to perform the "Intersect operation" within the group's editing context).

sorgesu · 23 Oct 2008, 22:06

If you do that, you won't be any further ahead. You still have to select the bits that you want to erase.
It sounds like you may not know the various ways to select that will make things easier. For instance if you orbit your view so that the bits you want to chop off are all facing towards the right of your workspace, you can drag out a Right to left selection window over the geometry that you want to get rid of. Stop your selection window just short of the cut lines. That will select all items even partially within the window. Once selected, just hit the "delete" key. To select only those items that are edge to edge or endpoint to endpoint completely within the selection window, do a left to right selection.

To select a surface and it's bounding edges, double click on the surface. To select all attached geometry "triple click
on the surface. ( can't use this above becuse the cut line is still shared by the other portion of the model so it is still "attached") Lot's more ways to select also.

You are doing a bunch of advanced stuff but I think you may be missing some of the basics that may make life a lot easier for you. Groups and components definitely being a biggie.

If you could post your model, and just explain what you would like to accomplish, ( multi-part group??? do it over and over again???) Maybe we can provide some input on how to accomplish faster and easier, yes?