TS Brep patch loft artifacts and problems

[cekuhnen]

the loft command here either fails or produces unusable geometry while

the brep and ts geometry is pretty clean

i know I loft trimmed edges a real no go in Alias so not sure if that drives the terrible surface generation.

[innovatenate]

I sketched some rails for the Patch Loft surface body and I think the results are a little closer to what you're looking for. It  seems to help with the bulging or the twisting when you have tangent or smooth continuity selected for the profiles. Take a look at the attached file and let me know if that helps. 

Thanks,

[cekuhnen]

mh the loft had still bad results but it fixed the twist problem

loft surface continuity seems to be not working well.

I guess it is the mix of loft continuity and rail constraints.

I add the rails and stil there are visible transitional problems with smooth (loft)

the rails of course 

Here all rails are smooth constraint - the loft is set to smooth so it should all be smooth and flawless but is not

the result got much better for sure. still I think behind what I could get in smoothness in Alias

[cekuhnen]

here one result with Smooth for Loft and tangent for curves and the result is bad

then when I tried to adjust the handles like scaling the tangent constraing value

this happened rendering the 3d sketch and constraint system again into a complex and painful experience

I start to think that while the constraints are cool Fusion really needs a serious blend curve too with better weighting options like any other CAD surfacing tool has.

I spend more time here on all this construction than I would ever do in Alias.

[deyop]

I may have missed something in this thread or confused it with another.  Why not create this as a single T-Spline?  This is the value of T-Splines to reduce the problem with managing NURBS transitions.  

Alias is a capable surface modeling package but it would suffer from this approach as well if it could handle it at all.  The double curvature inflection on the one side is a real challenge.  This feels like asking for trouble.   The tangency is obviously failing you as indicated in the image but driving the transition with curves in this area could be a problem for any strategy.

Blend curves have a nice interaction.  I know coming from an Alias background the Blend curves feel integrated in applying constraints during construction where in Fusion we create the sketch entity and then apply the constraint.  We can learn from that.

[cekuhnen]

Hi Paul,

First the student should learn the art of NURBS first before they even touch TS because they would refuse anything else. Sad but true. Also TS requires careful placement of CVs. What is easy for us stresses them. So this is the educational goal. Changes are much higher after they graduate they will have to deal with NURBS than TS.

The second problem with TS is the quality of the surface it creates compared to Alias or other NURBS modelers. TS runs fine in Fusion but exported as STEP is pretty heavy and not suitable to be CV manipulated.


But besides all this and I personally would use TS of course, the loft tool still needs refinement or the workflow because in my last posts you can see that the results are not ideal.