SK's Alias learning journey - help welcome :)

[Anonymous]

Hi I'm SK and I make 3D CGI stuff using polygonal modeling for 15 years now, working in differents fileds such as video game/architecture/product design.

I decided to learn surfacing and CAD modeling just because I'm addict to hard surface modeling and want to move to the next level. I'm already a pretty good user of Fusion360 but the real deal is Alias, and my learning curve on it is pretty slow I admet. Not easy to think in surface with my polygonal background ^^

I'm opening this thread to share with you my struggles and question with the hope that some of you can help me on my learning of Alias 🙂

As a start here is an issue I fall in pretty often:

I had two surfaces that interacted each other, then I trim them in order to create a gap between them and the goal is to fill it with G2 curvatures surfaces to blend them together.
See the two following screenshots to see what I'm talking about:

The biggest problem here is the round corner... I tried everything I know... Square, Brail, custom blend curves to divide the space in multyple squares... and of course manua alignement after all of that but I cannot get it done !

What would be the proper way of bridging these two surfaces together ??
Help will be appreciate 🙂

[brian.osborn]

Hi SK, its quite difficult to answer questions like this without more information, however a few comments,

• Its a lot easier to understand surface issues and solutions if you show the CV/hull layout, sometimes its obvious what the issue may be when you show this, without almost impossible.
• Likewise its best to use the explicit control options within the tools to ensure that your surfaces are not becoming to complex, especially if running off trim edges ( shouldn't be too much of an issue running of natural surface edges)
• Did you try intersecting these two surfaces and using the surface fillet tool, maybe using the 'variable ' option if you wish to taper the fillet ( but don't add too many constraints)
• Sometimes you just don't need G2 on an internal fillet surface G1 may be acceptable, it depends on the final use of the model, if just for visualization then G1 probably enough
• Its not going to be possible for alias to build a G2 blend in your model as the main long fillet surface has a continuity issue anyway, so therefore subsequent surfaces will also inherit that problem, fix that edge first and you may have more success.

Good luck, maybe you can help with some polygon modeling issues in the future.....

Brian.

[Anonymous]

Hi and thanks for you feedback and yes I knew I cannot get a clear answer of how to do it because my struggle is more a way of thinking and how to construct the shape that I want.

Yes I tried the surface fillet but the only type of fillet that works is the radius one and the issue is that on the corner it became mega tiny in comparaison of the rest of it. I tried to control it via the variable radius but then the shape of it became "wavy" (= not straight) so it wasn't good...

I will try a different approach as soon as I have time and I will post it here to share and see if I improve it or not 🙂

[shinji-pons]

You could try a few things:

1. freeform blend tool between the two trimmed surfaces with G2 on either edges
2. insert blend curves on either side and use square or even birail
3. or like you suggested multisurface fillet set to chord instead of radius to make the fillet appear more regular, but this approach won't give you much fine control over the surfaces and fixing problems over many CVs is very inefficient

Could you share the file please? I would like to have a go 🙂

[Anonymous]

Hi Shinji,

I tried all 3 solutions that you propose but I didn't get it done ... I'm still a noob at Alias so maybe I just don't use the tools correctly.

A file .wire with just these surface and my adept to freeform blend is attached 🙂

[Anonymous]

I started the shape all over again from scratch and here is my current result, not perfect but way much better don't you think ? (see attachement) 

here is my process:

1. I created the top curvy shape with 4 clean curves and use the square tool to create the surface
2. I draft vertical new surfaces from edges of the surface I juste created. These draft surfaces intersected with the "ground"surface (the big one).
3. First I focus on creating good round bevel and corner between the curvy top surfaces en the draft ones.
4. I created and projected curves on the ground surface and others on the new bevel surfaces.
5. I created vertical blend curves from the new curve on surface on the bevel to the ground. Like that I have smaller sections to work with.
6. I used the square tool to create new surfaces between all of this.
7. I aligned them as good as I can, only 2 are not G2 with a error around 0,6 which in my this particular case will be enough for my need (visualization, it's a small object so not so visible).

If you have any feedback or better way of doing it, feel free to share 🙂

[shinji-pons]

OK I got it to work but it's very far from Class-A standard, but for concept it will do just fine. There are a few problems in your file that I would like to point out:

• your geometry is super small, the width of your "thing" is only 4.58 mm! A nail clipper is much bigger than that and bigger geometry will also help with tolerances and moving CVs in a more controlled fashion.
• you are trimming a lot of stuff away on your horizontal surface which is ok but if you keep it four-sided and are not afraid to lose theoretical edges then you can use Trim Convert to have natural edges instead of trimmed edges.
• the "bump" surface is quite heavy (degree 9 in U direction) which suggests that it's doing too much work so you could make the whole bump using more surfaces.

About making the fillet:

I tried a few things but the corner as you mentioned is causing problems and tools like Square do not give a good result. So I extended the bump surface so that it intersects with the flat surface. With intersect, I could see that it gave me a pretty nice curve on surface. So I used multisurface fillet with Chord with G2 on both sides and it worked ok. The surface quality of the fillet is far from high but it gets the design intent.

I attached the file so you can see how I did it.

[Anonymous]

Thanks a lot Shinji for that feedback and all the knowledge you deliver.
mmmm I have to check my scale, I have made an mistake for sure, thanks for pointing this out 🙂

I have to try to use more the trim convert yes, I actually not sure what it really does in comparaison to the regular triming tool and when to use it or not ?

I learn some stuff from your feedback thanks, it really helps me on my journey 🙂

I will look into your modified file later (I'm not at home now) but huge thanks for the time you took !

Did you saw my previous reply ? I did get a pretty good result by starting over with a little different shape for the bumpy surface.

[Anonymous]

I checked your modified file and wnat to thanks you, it's a way more efficient way ! untrim and directly surface blend between them, it's the best result I got so far, thanks

Just a question about that: I have an other similar case that you can see in the screenshots attached, but when I produce the surface fillet it goes the wrong way... how to reverse it ? thanks

[shinji-pons]

After you pick the surfaces in multisurface fillet, you see the pink and yellow arrows. They tell you how the tool will orient the fillet. You can click on each one to flip it’s direction. I also like to stay in curves on surface mode  instead of automatic so that I control the trimming. 

[Anonymous]

Oh ok thanks for the information and tips I really appreciate your help, thanks a lot 🙂

[BarryKimball]

 Since Alias now supports subd modeling, basically the same as polygon modeling but limit surfaces are created, you could try using Alias to model as you do in other polygon modeling software's...

 I had too much to say for text so I decided to make a screen cast...I hope it helps you understand some of the nuances in surface modeling...the screen cast is below, its my first screen cast so hopefully it works for you...

[BarryKimball]

I cannot see the screen cast link...here is a link...

https://knowledge.autodesk.com/community/screencast/78fdcc0f-70df-4786-940a-63a2fd5e9027

paste this into you browser

[shinji-pons]

Thanks for the video Barry - I learned some really good things to watch out for in my own models. 

[Anonymous]

Sorry for the delay guys, I just became a Dad 11 days ago and living on our private bubble for a while (and still do ^^)

BIG THANKS to 451776 for this amazing help and for the time you took to explain all of this!

I learned a lot in your video!! You point exactly the issue I have trying to learn Alias on my own with my polygonal modeling background, is the way of thinking the process to get the shape I want which is totally different.

I will keep working on this tiny model (after fixing the scale issue, even if in real life it's a object around 6-7 cm long) as soon as I have time and energy (not soon I guess :P) but a huge thanks to you again !

PS: In this forum is it preferable to open a new thread for every issue we may have that way we can accept a solution ? (I opened this thread with a general title because I didn't want to "spam" the forum with multiple threads everytime I need help, so I though maybe one big thread could be a good idea, but maybe it's not. Let me know how this forum is supposed to be used )

[brian.osborn]

Congratulations! I guess that maybe you will be a bit busy ( and very tired) for a wee while ......