Michael,
After seeing the way you used trim instead of the way I used bool diff, is it an either or, or is there an advantage to my model geometry to do it with trim?

Thanks,
Burr

Hi Burr,

> After seeing the way you used trim instead of the way I used
> bool diff, is it an either or, or is there an advantage to my
> model geometry to do it with trim?

Hi Burr, it all depends on what shape you want at the end - I was going for a kind of "thin wall" type shape without much bulk.

Your one is just as valid, but it has more material in it, more of the inside of the sphere remains in the way you did it.

If you have a solid and you want your result after cutting to be a solid, then boolean diff is the way to go though.

Another alternative way for the one I did would be to do the shell on the uncut sphere first, and then do a boolean with the cutting curve like you show, it just isn't quite as clear of an illustration because it is harder to see the thickness on the uncut sphere...

Booleans and trim are related functions - basically booleans are a shortcut for doing a trim and then automatically deleting certain parts (to the inside, outside, etc... depending on whether it is a difference/union/....) then joining the results together.

I was kind of focusing on the initial shape as more of a surface model instead of a solid model - for surface models (a surface that does not enclose a volume), then you tend to use Trim more often for that because the booleans are more oriented towards volume operations.

- Michael

Just a bit of work from the inspiration of this thread.
Rendering in Carrara6Pro.
(Is Brian having fun!??)

Brian

Thanks for all the input guys.

Ok say I didn't want to create the main shape from a sphere or I needed it to be more specific shape wise? I thought I could go about it thus.
Create a curve like this then put a connection over it and then run a network command over it.





Unfortunately doing that produces this!


Could someone tell me what I'm doing wrong?

maybe you must try something like this ;)

Thanks Pilou! I never thought of that. trouble is doing it means I get a kink at the top?

How would I get rid of that?

Like this ;)

Hi gizmo,

When using network you will need to split the curves into a UV network frame (basically having curve running in X and Y).

I have attached a simple example:-

So 2 méthodes with advantages and disadvantages :)
(Sweep 2D = Sweep 2 Rails)

Thanks for the helps guys its really appreciated.

What I don't understand though is how you created those curves Manz?

Here:


And Pilou, how did you do you 2D Sweep!?

Just select the Profil (uper round top curve)
Call Sweep function
Click Rail 1 (one curve)
Click Rail 2 (second curve)
Done or Right Click
That all ;)

You can train with my previous send 3dm file (post 1952.15 )
Select the right object's surface
Delete the surface and you can make that I wrote above ;)

Ok I see.

One extra thing I'd like you to explain. Presumably you used the model Manz created. If so how did you redivide up the curves of his original model into your new one with only 3 curves??

Just select curves that you want and call function "Join"

If you want make some cuts in a curve just draw a line (or a curve) from the spot wished and call function "Trim"

Hi gizmo - there's also some extra information on how to arrange the curves for Network here: http://moi3d.com/forum/index.php?webtag=MOI&msg=1905.1

For Network the curves need to be arranged in a particular way that can be unwrapped to a 2D grid pattern. If your curves are not arranged in that way then it will still get forced to be like that and you can get some strange results like your first one there.

- Michael

Hi gizmo,

> Ok say I didn't want to create the main shape from a sphere or I
> needed it to be more specific shape wise?

It seems like you're still focusing on things a lot from a polygon modeling perspective? I mean here you're focused very much on the final edges and drawing those first.

It is possible to do that like Manz shows above, but really it can be a lot easier if you build a bigger shape that has the surface that you want, and then trim it back.

So if you don't want a perfect sphere as your main shape, draw a different profile and use Revolve or Rail revolve to create a different surface shape, then you can trim that using the same steps as was done with the sphere originally.

For example, if you take these 2 curves, and select the half one as the profile:



Then you can run Construct / Revolve / Rail revolve, and pick the longer one as the rail curve, and then pick the revolve axis between the 2 ends of the open curve, and you will make this kind of "customized sphere":



Also after you have completed the rail revolve, you can turn on control points for the curves and adjust them to update the revolve.

This can be an easier way to create a more customized starting surface because there are fewer curves involved to define it, and it will avoid some of the problems of trying to create a surface to a more complex boundary directly, which is possible but tends to be hard to control where points pinch together.

It takes a bit of getting used to if you are used to polygons, but with NURBS it can often be a good idea to build things larger than you need at first with more simple curve layouts, then trim or boolean them to produce your final result, rather than trying to build to the final outline directly.

- Michael

>>What I don't understand though is how you created those curves Manz?

When you have 2 standalone curves (as you have colored green) you can simply make a Construct~blend between the 2 curves (use G2 to keep curvature)

Many many thanks for all the help guys. I feel like a whole new world is opening up for me.

A quick question for anyone else still reading the thread. Can you only Boolean closed objects? I tried to union boolean the outer shell I created with the sweeped circle and all that was left behind was the sweeped circle? Should I have closed the main shell for it to work?

Right hold up I'm experiencing problems again. I've got the shell exactly how I want but how do I close it? I thought I'd simply create another curve cage but make its thickness a little smaller than the original. Ho there's numerous problems with this.
1) Copying and pasting the cage and moving it to the side to alter. How do I then get it back to exactly the same position? Object snape doesn't seem to work?
2)Because I can't get it back to the original position exactly it's out of place. When I do a Join command on the 2 shell pieces nothing happens? I'm still left with 2 pieces?

Here's an illustration of what I mean. How do I get these 2 componant to be snapped together exactly.

>>>Can you only Boolean closed objects?

Read the help file:- http://moi3d.com/1.0/docs/moi_command_reference7.htm#Construct_Boolean

Thanks Manz.

Anyone know how to snap the 2 shells exactly?? And then Join the two shells together to form one part which I can then perform a union Boolean with?
I want to go from this

to this

Hi gizmo,

> How do I get these 2 componant to be snapped together exactly.

Pick all the original wireframe and drag it from the end of that highlighted curve indicated by the arrow and there should be a corresponding point on your model to snap to as shown.


Cheers
~Danny~