NURBS or SubD?

[SJD]

Hi

I'm trying to get to grips with more complex modelling tools in FZ 8.6. I'm trying to construct something similar to the cosmetic bottle in the picture. I've used Subdivisions for the main shape but have found it difficult to construct the cap accurately with the same method so I am trying to use NURBS surfaces for this task. I've read that SubD's are great for concepts and more sculpted forms but NURBS are better for more accurate representations like product design.

I've watched many of the FZ tutorials and have settled on this method but I'm still having trouble. Specifically, it's the indent in the cap (circled) - it looks so simple. I've managed to create the models in many of the tutorials without any problems so I must be missing something!

The images just show some basic tests - I have created a basic cylinder and converted it to a NURBS surface. I've then created 2 options - a half circle indent and then a rounded square (more like the result I want). I then slice the profiles into the caps and try to loft or blend between the resulting shapes. The circle is fine but it's the square version I can't manage. I've also tried cutting a similar shape into a solid object and then using the rounding tool but again, no success.

As always, any help would be greatly appreciated 😀

 

 

[snow]

try starting with a large cylinder for the cap and a small cylinder for the notch and boolean difference the two objects.  then use rounding to make the corners nice and soft. 

[SJD]

thanks snow

yes, I have tried that method and whilst it seems to work sometimes it seems a bit hit and miss depending on the shape that I difference from the main object. If I angle the sides or taper them I get error messages. I was hoping there might be a more accurate and reliable way to do it

[¢hris £und]

I Have used tangent loft quite extensively and works well for me.  In fact, I would consider it one of the most useful tools.

if you can't get it to work, then use the NURBS blend as you did, but only on the top and sides.  Use the N-bounds tool to fill the fillets.

 

below, is something like what you are attempting, using the Tangent-Loft.  File attached too.

Cap-not to scale.fmz

[SJD]

thanks Chris

that's exactly what I was attempting using the tangent loft but for some reason FZ keeps crashing, I must be doing something wrong (at least I'm on the right track 😎). Thanks for the files, I'll take a look.

In your opinion, is this the best way of approaching this? It's becoming evident that learning how to use tools is only half the battle, learning when to use them is a lot harder!

cheers

steve

 

[¢hris £und]

It is how I would do it.  I did notice a little different in the beginning approach.   I used a single cutout and scaled it down.   Maybe this is why I succeeded.

There are times when as noted above, that I need to use the n-bounds in combination with the Tang-Loft too.

 

I find the Sub-Ds to be excellent for loose-flowing shapes.  But when I want exact, I use some combination and Tang-Loft.   Don't forget, you can convert Sub-Ds to NURBS when you need the best of both.

¢£

Edited May 29, 2020 by ¢hris £und

[Gyro]

For someone that is not conversant with the more advance lofting tools I'm finding this very helpful, using the file as a template to learn the ropes, is there a decent tutorial anywhere you can recommend.

Thank in advance Andrew

www.gyro.co.nz

 

[¢hris £und]

The tips and tricks page may have a brief on it.   Additional tricks would be:

Do your best to align your seams or segments/points so that your lofts can blend. without twisting or stretching too much.  If you need to, split a NURBS patch, or use the Trim/split of various methods to force segments and seams to align.

I usually work every other loft, applying the lofts to the easiest sections as best I can.  That way, if a loft doesn't work, the n-bounds typically will work.    Do your best to n-bounds with 4 bounds, not 3.   It will do 3, but you are not guaranteed a nice transition between all patches.  (it actually doubles up corner points in one of the 3 corners)

Sometimes you will notice that a patch does not align with an adjacent patch... That usually is ok.  When you stitch the patches together, fZ is brilliant enough to fix them.  Most of the time, you will notice these when a n-bounds and a loft are adjacent.

I hope this helps!

 

Tech,  One thing that gets in my craw is: When Tang-Lofting.  The Tangent checkmarks should be checked by default.  Or have the option to set as a default.  As that is pretty much the point of the tool.  Thank you!

¢£

[¢hris £und]

Gyro,

Here is a freeform design (no plan).  Really it is just some ugly sci-fi nonsense, but fun to play with.  It is far from complete with many areas yet to solve.  But if you look closely, this is done with NURBS patches and a combination of NURBS blends, tang-lofts, n-bound and what ever else I could get to work.

If you look closely, you can see on the bottom of the main fuselage, the section lines that I had to cut into the 1 NURBS patch in order to get the complex shape to be able to stitch in.  The cockpit area could be water tight, but there are some areas that I just don't like yet, so it isn't there yet. 

First image is prior to splitting it. The rest show it split and using those splits to tang-loft to the intake cowling.  Which had to be split because of the internal geometry of the intake.  blah blah blah.

Really, it is just an exploration of how far I can push some of these tools.  Me being one of the tools.

 

[SJD]

hey Chris

thanks so much for your help, could I trouble you to back save that example to 8.6? (the cap, not the sci-fi project!)

using a single open shape for the cut and re scaling has made a difference and I am now able to loft, although there are mis-matches between the straights and the fillets at the moment

when you loft, do you do it a section at a time?

 

[¢hris £und]

If I get such a large mismatch where it can't stitch, I would do the straights, then use the n-bound to fill the curved sections.

 

Cap 8-6.fmz

[SJD]

great stuff!

thanks Chris