3D sweep around corners and angles

[sam1808]

I have been trying to make what seems to be a pretty simple 3D sweep and it refuses to work. What are the known limitations of this function... is there a maximum number of segments? are there angles that don't work? It would be great to hear how people get around the problem, or if autodesk are planning to make it more effective.

[beegee]

Sometimes a sweep will have problems if its profile returns over itself. Hard to explain in words.

Can you post an image of what you're trying to do ?

[David Conant]

When constructing sweeps, they will fail if they become "self intersecting". In non mathematics terms:
Revit sweeps the profile along the path keeping it perpendicular to the path at all times. At corners and tight arc radii in the path, parts of the profile that lie inside the path may swing back against the direction of the sweep as the profile sweeps around the bend/corner. (like the hinge end of a balanced door) In this case the math begins to fail as the shape intersects itself. Careful profile construction and path layout can reduce this problem

[PeterJ]

David

On this basis it would seem to be the case that any swept solid that sat both sides of the path would fail and we know this not to be the case. Is there a limiting radius or is it a case of trial and error?

[David Conant]

Failure will only accur when the profile extends past the centerpoint of the path's curve. Imagine you are bending a piece of pipe. Without cutting the pipe, there is no way to bend it so the centerline makes an arc with a radius smaller than the radius of the pipe itself. (in reality the pipe bend radius can't even be that small, but virtual stuff can be squeezed and stretched more easily)

[beegee]

Very poetic David. Leaves my feeble explanation for dead.

[Arnel Aguel]

Will it be possible to adopt the code for lofting in max/viz because 3d sweep function is similar to lofting in max/viz and it is very powerful without any glitch and so many variations to its capabilities.

[PeterJ]

Thank you David. Even I can understand that.

[sam1808]

thanks for all that discussion, yip, i'm getting it...

does anybody have an answer to Arnel's question? I agree, it would be tremendous to have a lofting tool something like those in rhino / max etc. Any chance in forthcoming versions?

[beegee]

Nobody, with the possible exception of Carol Bartz, knows what's going to finally appear in R6.
And Carol's not saying.