Hi Rob - yeah normally you would do as Anis shows there and do an extrusion from the side followed by a trim to produce a cap on that kind of an arrangement.

You can use that method any time the profile is a distinct 2D shape as seen from the side.

Sometimes it can be easier to extrude something like that as a tall block and then use 2 cuts to slice off the ends to produce the angled results, that way everything stays as a solid through every step. See this recent post for an overview of that method:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2614.10

When you have a more irregular hole to fill that does not have a single distinct side profile, then it becomes a much different situation. That's when a NURBS tool called "N-sided patch" can be useful to fill in things, but MoI does not have that particular tool yet. If you need an more wavy surface as the cap, then it usually becomes easier to build the base piece as an extended solid and cut off the end by booleaning it with the surface so that the surface becomes the cap as it cuts the solid.

Let me know if you need any more info on these other methods, but I think the link above should help give the picture.

- Michael

Thanks but yes I thought I might have chosen a poor example as I agree it is easy to just trim this shape from the side but Michael is right I was refering to this type of situation that would work whatever the shape, so it would work in situations where you couldn't get an exact side elevation to trim along as is often the case with roads/terrain layouts. N sided Patch sounds like the answer, any ideas on when this might emerge? Is it a V3 thing or a V4 thing?

Cheers

Hi Rob,

> N sided Patch sounds like the answer, any ideas on when
> this might emerge? Is it a V3 thing or a V4 thing?

I hope it will be a V3 thing, but it is hard to know for sure - it can be a rather finicky thing to make work well, some of the typical mechanisms that are used for it tend to be rather prone to making oscillations in the surface.

But also it looks like there is a good possibility for me to license a 3rd party library to help with this.


In the meantime the way you would generally go about it without that is more like the following.

If you want to get a result with an irregular wavy filled piece, like for example this:



Build the wavy part as an extended sheet, using a surface construction tool like Network or Sweep (here I used Extrude with "set path"):




Then make your base shape a big extended block:




Now select the block, and run Boolean difference, and pick the surface as the cutting object. The block will be carved into 2 pieces:



Delete the upper piece and you will be left with the result:




Even when there is an n-sided patch tool available in the future, it can actually be better to use this method when it is possible, you just get a lot more direct control over the surface shape. The n-sided patch kind of cooks up something automatically for you and there can be a variety of difficulties with it, sometimes it is hard for an N-sided patch to pull the fitted patch to a tight tolerance of the input curves if you have a detailed hole boundary with a lot of segments... But when you do it by surface intersection as shown above that guarantees a nice join between the results.

- Michael

Some interesting techniques.
I would just do it as a sweep. Select the top edge of each of the long sides going down the hill, including the curved parts all the way to the bottom. Copy-paste to create lines and Join each if necessary, then choose the narrow top edge and Sweep with the two downhill lengths as rails. As long as that bottom edge is a straight line it will work great. If there were curving on the bottom edge then I would just extend the point of the rails fully past the curve and after Sweeping use the curve bottom edge to Trim the surface.