Tangency of loft surfaces

[TheTick]

I would like to hear from anyone who may have noticed this...

Has anyone noticed how the tangency controls for lofted surfaces are not terribly accurate? I have made lofts with tangency constraints to surface edges that have been off-tangent by over 4 degrees! Using guide curves alleviates but does not always eliminate the problem.

Simple test for tangency of a loft surface to its controlling surface at a point:
1.) use 3DSketch to place a point on an edge
2.) make an axis through the point an normal to one of the surfaces
3.) make another axis with the same point and normal to the other surface
4.) measure the angle between the two normal axes

I have verified the non-tangency conditions before by exporting parasolid and importing to UG.

Someday, someone may kill you with your own gun, but they should have to beat you to death with it because it is empty.

 

[SBaugh]

Have you tried making more profiles?

Regards,

Scott Baugh, CSWP
3DVision Technologies

http://www.3dvisiontech.com

http://www.scottjbaugh.com

faq731-376
When in doubt, always check the help

 

[TheTick]

The point is that SW should be generating surfaces that meet the tangency restrictions if they end condition is so specified in the property manager. I know it is mathematically possible. Also, I have had a chance to compare against Pro/E and UG using the same sets of surfaces and edges. They generate the tangencies without error with the same number of defining profiles. A good example for this is one that is common in industrial design applications: making a fillet blend that has tangencies controlled on both edges.

Sometimes adding profiles hurts more than it helps. There is a tendency in organic modeling to throw in more control points (in 2D) or profiles and guides (in 3D) when what is really needed to adequately define the form is curvature and direction (tangency).

Someday, someone may kill you with your own gun, but they should have to beat you to death with it because it is empty.