Same here, I use them as both.  It's also a way to simply organize and keep 
track of what you're building (when I have a hierarchical view.)  I nest groups.
 
If I have sub-models that deserve to be in their own project for reuse 
elsewhere, then it would be handy to link files into a project.  Those linked 
"external sub-models" wouldn't be editable in the project (to keep it simple) 
but you could double click them to launch an additional instance of LeoCAD to 
edit the source sub-model file.  Right now I merge external sub-models into the 
project and immediately assign them to a group for that sub-model.  When I 
fixed the file merge, I almost added the ability to automatically group the 
whole imported model for this very reason.
 
One design I have was for a functional train track bumper (for the older 
4.5V/12V systems.)  It had a stationary base and tie, and a moveable bumper 
that was spring loaded by a rubber band.  These two parts must be independent 
of each other and so everything I did with these two 
groups/sub-models/selections was separate.  
 
Part of my attraction to the hierarchical group management is because that's 
how I have done things for so long.  I create a lot of diagrams and graphics 
which can involve lots of hierarchical layering to get the masking effects you 
want, or just to stay organized, so it comes natural to me.
 
I never thought of saving selections.  I can't think of any scenarios where I 
always want to go back to a certain selection that is more complex than just 
clicking or control-clicking on a few things.
 
- Rod

 
Date: Wed, 8 Jan 2014 11:00:56 -0800
From: [email protected]
Subject: Re: Patch: Group Toolbar
To: [email protected]
CC: [email protected]; [email protected]

It's been awhile since I built that BI, but as I recall, I used groups for both 
purposes:  sub-assemblies and selection sets.

I recall thinking at the time that I could REALLY use sub-assembly support in 
LeoCAD. I would end up creating entirely new files for each sub-assembly so I 
could show sub-assembly steps in a callout.  Most of what I wanted would 
require that LeoCAD head more in a desktop-publishing direction than a CAD 
program, however.  

I thought it would be especially neat if I could define sub-assemblies in the 
main assembly, go into a display mode that showed ONLY the steps of the 
sub-assembly (while I was working on those steps), and also the ability to 
define the first main step that the sub-assembly showed up as an "explode" 
step, so the sub-assembly (as a group) would have a different position
 than it normally maintained in the model.  [At all times, I was happy to use 
InDesign to add arrows to the final product, I never saw it necessary to have 
LeoCAD do that job, and in fact I was using LDView as my renderer as well, 
rather than rely on LeoCAD to output the BI]

Having to specifically load and save selection sets sounds like extra steps 
that would be annoying.  Saving them as part of the file (as groups are now) is 
definitely better, IMHO.

     -- joshua


        From: Leonardo Zide
 <[email protected]>
 To: Joshua Delahunty <[email protected]> 
Cc: Rodney Rushing <[email protected]>; "[email protected]" 
<[email protected]> 
 Sent: Wednesday, January 8, 2014 11:46 AM
 Subject: Re: Patch: Group Toolbar
   

I was rewriting groups way but this conversation is making me rethink their 
purpose.

So what do you (and others) use groups for?Would you use groups if you had 
sub-models?
Do you need groups to be nested?Would it be better to save selection sets 
instead?



On Tue, Jan 7, 2014 at 11:36 AM, Joshua Delahunty <[email protected]> wrote:

For what it's worth, I used groups extensively when building the BI mentioned 
here:


http://www.technicbricks.com/2011/08/building-instructions-for-nathanael.html

So they definitely have their use, in the current incarnation (at least, in the 
pre-Qt version of LeoCAD).


    -- joshua


  
      From: Leonardo Zide <[email protected]>

 To: Rodney
 Rushing <[email protected]> 
Cc: "[email protected]" <[email protected]> 

 Sent: Tuesday, January 7, 2014 12:23 PM
 Subject: Re: Patch: Group Toolbar
   


The original idea was just to make it easier to select pieces that are always 
locked together (like a tire and wheel) and be a replacement for sub-models. 
Maybe groups should have been selection sets instead and have sub-models be 
used for complex groups.


And that's why I don't like the current groups, it doesn't replace sub-models 
and doesn't help with selection either because it tries to keep all objects 
selected at the same time.

I don't like changing things that aren't visible so you end up being 
inconsistent one way or another. Maybe drawing a faded version of the invisible 
pieces in the group is enough to show what's going on.


On the code side groups are a terrible hack also.


On Tue, Jan 7, 2014 at 8:27 AM, Rodney Rushing <[email protected]> wrote:


> Groups are something that I never finished implementing



What was your original goal for groups?



I don't think there is a problem with groups as they are (perhaps some 
additional internal structure to make it more efficient to isolate groups 
instead of scanning the whole piece list - but I also like the coherence of 
having just one list.)  All that seems to be lacking are (1) information to 
make the user aware of how the operations are applied, and (2) consistency in 
how operations are applied.





If I knew render view operations would always apply to invisible pieces of a 
group, and there was something to tip me off that there are invisible pieces in 
my selection, I'd be satisfied.  I do sometimes wish I could position a 
sub-group.  The group toolbar is a way to do the selection, but the core logic 
that I didn't want to change is not aware of how to operate at a specific group 
level.  That seems like an easy change.





Also, multiple views of the data are a big help in understanding your model and 
manipulating pieces within the group irrespective of how they are represented 
in some other view.



- Rod





________________________________

> Date: Mon, 6 Jan 2014 17:04:24 -0800

> Subject: Re: Patch: Group Toolbar

> From: [email protected]

> To: [email protected]

> CC: [email protected]

>

> I was on vacation and I'm just catching up with my emails.

>

> The reason why there are steps and frames is because LeoCAD used to

> have an animation mode where you could create simple animations using

> key frames and you could create animations and instructions in the same

> file. I've decided to remove it because it's not the main focus of the

> application (building instructions) so it adds to confusion and feature

> bloat.

>

> Groups are something that I never finished implementing, it's weird to

> have objects that are not visible be part of a group because it's not

> clear what should happen when you move the group. If you don't move the

> hidden objects the group will be wrong later but if you move them then

> you're moving something that's not visible.

>

> To be honest I think groups shouldn't exist in their current form,

> having a parenting system could be a better way solve the problem

> because pieces would always be relative to their parent so moving the

> parent automatically moves its children, even if they are hidden and

> more complicated groups that need multiple steps would be sub-models

> instead. I was actually implementing this system in my current work

> branch

> (svn.leocad.org/branches/model<http://svn.leocad.org/branches/model>).



>

> BTW, I usually develop new features in a separate branch so please post

> something if you plan on writing big features so we can try to avoid

> conflicts.

>

>                                         


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