lofting restrictions

[cuwaert]

Hi all, has anybody a complete picture of the lofting restrictions in Autocad.

The manual certainly isn't complete, there must be some hidden requirements for guides and curves. Must curves be curves or may it be sectioned polylines? What about the UCS, does it matter where it is? I have 2 sections I can loft, and then a bit later I can't and checked over and over if the guides touch the sections, if the guides are cubicked polylines.

[ReMark]

There are many sources for information regarding AutoCAD commands and how they work from the User's Guide, AutoCAD Help, after-market AutoCAD books, to online resources (ex. - Ellen Finkelstein's website or CADDigest). Try another source.

[JD Mather]

Just a couple of tips:

Sections should have the same number of base entities.

Rails (guide curves) should be tangent continuous and intersec sections at logical locations.

 

Beyond that the Loft in AutoCAD is very limited. There is far more control in a modern 3D CAD program like Autodesk Inventor.

 

Can you attach a loft that you are having difficulty with?

[cuwaert]

Thanks for the replies guys, they were really helpful.

Lofting is a very uncertain business in acad, that's about the conclusion I have to take. Sometimes it doesn't work and by doing "something" such as curving quadratic in stead of cubic it suddenly lofts. The next time I try this on another item it doesn't work.. so I have to work around it en that's what I did. I don't seem to get the hang of it, what does the trick in one case doesn't in another.

 

Concerning my work, it's just for fun, so no big deal, I can work around to get what I want, but I will not be able to make a nice sleak 3D modell to show off with:wink: but I will be able to make a 2D drawing to build the modell...as I allready did for several years now and at the end, that's what it's all about.

My PC is pretty slim for 3D modelling (1.6GHz mono core, 750MB RAM and videochip onboard using 64KB of RAM) . In a few weeks I have another more apropriate machine and then I'll try Rhinoceros and hope in the time I get to evaluate, I will have a sufficient picture to decide what to do, stay with acad or sack it.

[ReMark]

Quoted from the book AutoCAD 2007 3D Modeling - A Visual Approach by Alan J. Kalameja:

 

"Guide curves control the shape of the lofted solid or surface.

 

Guide curves control how points are located on cross-sections are matched up to prevent undesired results.

 

Guide curves must intersect each cross-section, must start on the first cross-section and end on the last cross-section."

 

By the way, did you know that if a cross-section is open the result is a surface loft. And if a cross-section is closed the result is a solid loft?