Now that you have the main extruded form created you can then get the ends formed how you want by slicing some material off of them with some profile curves.

So go to the side view and get your profile cutting curves arranged how you want them, something like this:



In the 3D view it looks like this:



Now that extrusion can be cut by those curves using a boolean command - you can select the extrusion and use Boolean difference to slice it up into pieces by those profile curves. If you have a closed cutting curve that will bore a hole, if you want to kind of cut things and not have holes for closed cutting curves removed you can instead use the Boolean Merge command which just slices everything up and doesn't discard any pieces even when you've got closed curves as the cutting objects. When using boolean merge you just select everything all before running the command instead of having the 2 stage selection process of boolean difference where base objects and then cutting objects are selected separately.

So anyway after using whichever boolean command is the most convenient you will get a sliced up result like so:



Delete the parts that you don't want to get the final result:




In general it tends to be easiest to get a curved end on an object in this way of producing it by slicing the ends off of an initial flat extruded block.

The other way that you can do it though is if you build a surface for the piece to extrude rather than just a curve - when you extrude a surface it is able to be capped because that surface can just be copied to the other end of the extrusion. That method would be to build a surface from the cleanly rebuilt 4-sided shape using sweep or network on it, and then select that surface and extrude it. However, the technique shown here of cutting the ends off is kind of more general purpose and more flexible, since you can have different shapes on each end including things like cut with concentric circles rather than a single copied circle shape like you will get with a direct extrusion.

Hope this helps!

- Michael

Thanks, Michael.

I understand this method of creating the solid that I want. (It does make me chuckle though, since that curved outline was originally created by mapping a flat shape into the inside of cylinder using the curve command...8^D)

I do have another question though. I don't understand when you should use the trim command to do something like this and when you should use the boolean commands. Your uses of the boolean commands are not "intuitively obvious" to me (as one college professor told me when I asked him to help me with the solution to a problem. He said that the answer was "intuitively obvious" and just walked away).

Thanks for introducing me to the "rebuild" command. I will use that in many different situations. I thought that that was what I was getting when I used the "join" command. Obviously not.

Mark

Hi Mark -

> It does make me chuckle though, since that curved
> outline was originally created by mapping a flat shape into
> the inside of cylinder using the curve command...

Yeah so actually you wanted to try and construct your starting solid directly off of that initial planar piece rather than doing a projection of it.

This is kind of a frequent mis-step in general - it's pretty natural since it is kind of easy to focus on the outer edges of the final result that you want to get. But often times those final edges are actually easiest to get from the result of a cutting operation rather than trying to create them directly as the first step.

When that's the case you need to kind of not worry about those final edges when constructing the first shape - instead try to get a basic simple and extended shape and then once that is in place cut it up. That kind of goes for a lot of different situations as well - like if you've got some kind of complex boundary for a surface a lot of times you won't want to build the surface directly along that boundary initally but instead build it as a broader and more simplified extended shape and then cut it to get the final boundary in place.


> I don't understand when you should use the trim command
> to do something like this and when you should use the
> boolean commands.

The trim command is a surface modeling operation - it's something that you would generally only use if you are working with some individual surfaces to build your model up kind of one surface sheet at a time. That's a different kind of overall strategic approach than working with solids.

You should generally use the boolean commands instead of Trim if you are working with solids - the booleans are focused on operations between volumes. So using a boolean to cut a solid will produce a solid result, leaving things like the extruded side walls of the cutting objects in place to make the result also a sealed off solid.

Using Trim will always cut a solid into a non-solid because it operates at the surface skin level and not at a volume level like booleans.

See here for some more description and visual examples of the difference between Trim and Booleans:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3883.3


You could basically describe Trim as more of a "low level" operation. The boolean commands are kind of like a high level cutting construct that basically combine surface trimming along with automatically detecting which pieces to discard based on volume containment, followed by automatic joining of things back into solids.

Sometimes the more low level approach of doing the trimming and joining steps manually can be useful for difficult situations, but if possible you can gain some more convenience and a more streamlined number of steps if you can use solids and booleans instead of low level surface trimming, so it's generally a good idea to stick with working with the solid modeling approach and use booleans when it is possible to do so.


> I thought that that was what I was getting when I used the "join" command.

No, the join command is more like a kind of grouping mechanism - it make a new curve object out of those segments, but the segments are still individual child objects of the curve, it doesn't do things like fuse segments together automatically. In the future I may try to do something like that, but there are other situations where it is not necessarily good to fuse segments together so it's kind of tricky to handle automatically.

- Michael