quick and nasty way is attatch the wall to a sloped Ref Plane. visually and in reality not correct as top of wall is not flat but if not to tight a radius looks OK.
Will watch this post for other solutions to a common problem.

I just got it to work. What I did was:

Drew a reference plane in plan view from one corner of the wall to the other (sort of like a chord) and named it.
Set my 3D view "orient to plane" and chose that reference plane.
Modeled an in place void family. Called it curved wall void.
In plan view, I used the grips to make it wide enough to encompass the entire wall I was trying to cut. I even let it cut the adjacent flat wall so the cut line woudl be exact (rather than editing that walls profile).
Used the cut tool to cut both walls. Finished the in place family. It worked great and only took a minute or two!

A lot of people discount the math involved in such a thing, but there are two possible scenarios:

1.

In elevation, it LOOKS like a consistant slope.
Done by: Using a void extrusion drawn in elevation, or by attaching to a reference plane / roof / floor, etc.
Top of wall: NOT flat, and infinitely variable, in terms of the slope in the perpendicular direction to the wall. In effect, any section through the wall would have a different angle at the top of the wall.
Slope: Varies, along top of wall, since the overall slope (shown in elevation) gets more severe depending on which point of the circle its on.

2.

In elevation, it looks like a spiral Staircase.
Done By: In-place void swept blend. Path = the walls edge in plan, profiles at each end = top and bottom heights.
Top of wall: Flat, when a section perpendicular to the wall is cut.
Slope: Has a consistant height change per degree around the circle.

A lot of people model (or draw) number 1, while hoping to get number 2 in real life.

There are at least 2 methods: let's say "A" & "B".

Method "A" is a model in place, and it's clearly expressed in the illustration provided by Revit when you hover the mouse over the Swept Blend tool.

The other method, "B", is to cut a wall element with a void that has a sloped surface on the bottom, similar to what Dan did.

Method "B" is better, for the following reasons: Revit has a bug in displaying a block or brick material on a model in place made with Method "A". The bug is that the lines that are supposed to be parallel, just follow the curve of the top of the wall, which is incorrect. On the contrary, Method "B" displays the masonry pattern correctly. The other reason is this: Method "A" does not let you change the wall type, since it is just a model in place, while in Method "B" you can change the wall type at will. Note: this bug about the hatch pattern still exists in RAC2012. It's known for quite some time now, but it remains there.

How good would it be if ramps could be more flexible. As voids or being able to attach to... endless possibilities

Hey Alf
No issue here using wall with brick patten and void Sweep Blend.
BTW good solution guys..:thumbsup:

ha! That's very strange, Mark. this issue has been there for some previous releases, and I tried it today in RAC2012, and still shows me the error. Well, it's good to know that it works in some cases, I just don't know in which cases, though.

Wait, did you say Void Swept Blend? That is a difference. Are you subtracting a swept blend from a regular wall instead of creating the wall itself as a swept blend?

EDIT: I guess this would be a Method "C". Even better.

Yup, thats how i would do it. A real wall type, and a void swept blend. =)

Real radial consistancy, flat tops, looks *real* in elevation. The way it should be.

Well, yes, that would be the best of both worlds. A real wall element, with the real geometry, and with the hatch pattern showing correctly.