tsplines: can I crease at a vertex?

[lukepighetti]

I can't seem to crease at a vertex. I have a flat plane that I'm trying to get to shape before I extrude it.

You can see a few places that are already creased, and two areas I would like to crease.

But when I use the crease tool, it creases both ends of an edge

Any ideas?

Is this the only solution, to add an edge and then crease?

[TrippyLighting]

Nope. But you can extrude your 2D structure into the 3D world and then add edge loops.

[lukepighetti]

Hm, yes I see that you can do that. But Fusion has created creases at verticies on it's own, not edges... why can't I do the same? 🙂 Is it a limitation of a tspline or is it a limitation of Fusion?

[deyop · Accepted solution]

The limitation is on which vertices are valid for creasing.  Basically only vertices that are shared at the corner of a single face are valid for uncrease/crease.  There is also a restriction on creasing interior corners specifically because they can only lead to poor surface quality.  We went to a redesign of the creasing last year that imposed those limits but the flip side is that we no longer created models which became "boxy" when applying creases in certain locations.  I think we need to do a better job of demystifying these rules.  I am attaching a PDF that hits the highlights of the changes we made to creasing. 

I know you may be frustrated by the transition from sketch to T-Spline model.  The advantages of T-Splines in terms of developing smooth organic shapes can also be a barrier when approaching it from a standard CAD approach.  I have a screencast here that may introduce some concepts for shape development that may help.  I am afraid I did not do justice to your design. 

Creasing and Sculpting

Thanks

[lukepighetti]

Hi deyop,

I want to sincerely thank you for taking the time to make that video.

I would urge Fusion team to include this video with TSpline tutorials and documentation. It's the best 'crash course' on TSplines in Fusion I've seen yet. Previous to your video, I did some studying with YouTube videos on TSplines in Rhino. I learned some new methods from your video though and I really appreciate it.

I will say that I had really good luck trying my best to make a plane that fit my sketch first, and then thickening/extruding, and then adding curvature.

I've included a video that shows what the result was.

I'm excited to try the bevel command on my next attempt, it looks invaluable for this type of work.

https://screencast.autodesk.com/main/details/e0dae188-61df-4f4c-a3c0-af50e51e233d

[lukepighetti]

Hi there, any thoughts on this result? I wanted a D shaped profile and ended up getting "sharp" edges where I wasn't expecting.

https://screencast.autodesk.com/main/details/b22ae38f-0b15-413f-905c-29e5cb8f5fb0

[TrippyLighting]

I'd actually include both of these awesome videos. The one shows methods of modeling with T-Splines and the other exemplifies the uniqueness and awesomeness of T-Splines in that when you're done with sculpting you can add mechanical features such as radii or simpy "drill" a threaded hole.

[dunderhead]

lp, two things to do when shapes misbehave:

• Repair body: to see if star and T-points have been toggled behind your back
• Check for hidden edges, which you actually can never see: the stem from isolated control points, or T-points, within distance 2 of star points.  And they spread!  This is obscure, see my posting and Jake's reply.

(It would be very helpful if box-mode showed you everything, star points, T-points, and hidden points and edges.)

[TrippyLighting]

@dunderhead
Somewhat unrelated question: What software do you use to make these animated gifs?
Also, Kudos for linking in that little thread. Very informative!

[dunderhead]

Thanks, trippylighting.   For the animations (such as the one you saw on how hidden edges affect shape): I use gimp*. It's slightly cumbersome!

-dh

*) Approx. workflow: alt-prt-screen, create->from clipboard, then, with updated window, alt-prt-screen, paste -> as new layer, then image -> crop-to-selection, then insert dummy layer, then filters->animation->blend, then export resulting layer stack as gif and check animate.

[deyop]

Nice to see the progress in the screencast you shared.  Based on the results I would like to make one more suggestion.  You may want to try Make Uniform command with the completed T-Spline model.  I am afraid I will fail to adequately explain the need for this but the short version is that when you have done a good deal of extruding, stretching and topology modification the transitions between faces can become "tense".  Make Uniform will "relax" the topology.  Why not just always keep the model "relaxed" after every operation?  Well as you will see the Make Uniform affects the entire model.  We don't want a single operation to constantly be changing the topology of the body.  So it is some special sauce that can help to improve overall topology.

Make Uniform Video

If we want a better explanation for the math under the covers I will ask someone from development to chime in.

Thanks

[lukepighetti]

Hi deyop,

I tried Make Uniform on my model. It did appear to 'relax' the model without changing the shape much, which is kind of neat. Something I'm not understanding though is it seems to show no difference in box mode. I was under the impression that box mode gave you full control over the nitty gritty bits of your tspline. It would appear that Make Uniform makes changes to tspline parameters/entities behind the scenes that we cannot access as users. Is that accurate?

Thanks for your help

Luke

[tom.finnigan]

Hi Luke,

I'm a T-splines developer, I'll try to explain what Make Uniform does.  I tend to over-explain, so I'm going to try to keep it short and practical.. let me know if you want more detail or background on anything.  🙂

Every edge in a T-spline surface has a positive number stored on it, like 1.0 or 5.5 or whatever.  This is sometimes called the parameter length or knot interval.  It changes how an edge curve eases into adjacent edges.  Make Uniform sets all of the knot intervals to be the same number, so the easing between adjacent edges / faces is always the same.

Why aren't these numbers shown in box mode?  Well, it's not the kind of thing that you can usefully edit manually.  There's a requirement that the knot intervals on opposite sides of a face be equal, and we've never come up with a better way to visualize it than just a number floating over an edge, so it can be a bit overwhelming.  In other applications we've experimented with optionally being able to show it, but it's not very useful to most users.

Why is it there in the first place?  The knot interval is required if you want to split an edge or face while keeping the surface shape the same (in Fusion this is called exact insertion mode).  The other options are making the surface bulge (like simple insertion mode) or splitting every single edge/face in the whole model, like a subdivision surface.

As an aside, if you're familiar with NURBS curves or surfaces, the NU in NURBS stands for non-uniform.  That's why in a NURBS surface you can insert a single row of control points without changing the surface shape.  It essentially splits the old knot interval into two pieces.  Make uniform goes in and makes all of the knot intervals the same.

From a very practical point of view, non-uniform edges are what makes the exact insertion mode work.  Some of the tools make non-uniform T-splines a little too easily , so early on in surface modeling if the surface gets pinched you can use Make Uniform to relax things a bit.  Once you're further on in the shape editing and have done some exact insertion to make small tweaks you want to avoid using Make Uniform, because it will change the shape of the surface.

Hope this helps, please let me know if you'd like more background on anything.

[laughingcreek]

Deyop-

Thanks for the the video and the PDF. Very helpful.  I'm going to have a few questions concerning the improved behavior of Tsplines, but I'm going to have to play with this a bit first before I can formulate them.

However, the biggest thought that hit me immediately was this- Where the heck did you get that PDF, are there more like it, and where can I find them?  (Tried searching in the help section for fusion to no avail.)

[deyop]

I am an user experience designer on the Fusion team.  When I work on projects like the Creasing improvements I try to keep a visual log about the features (and drawbacks).  This is also the basis for learning materials.  I PDF'd my powerpoint for your benefit because it was very specific to the topics we were discussing.  We may have dropped the ball in translating that visual log into release learning materials when the improvements came out.  My apologies for that.

I'd like to take the opportunity though to get anyone's input on how you are tracking down learning materials and what you think would be more effective.  We'll be listening so please be frank.

Thanks

[laughingcreek]

The bedrock learning tool that I use the most for any program is a well indexed help/reference section.  I will spend a lot of time trying to intuit my way through a piece a software, and being able to look up various commands I see in the menus is pretty important.  (I occasionally come across things in fusion with no reference in the help section at all).   I hate to sight someone else's cad system as an example, but I really like the way Rhino does their reference.  In addition to having a pretty good explanation for every little thing you could possibly find, they often have an animation demonstrating the use of a command or parameter sitting right next to it. 

Videos are useful also, and I do use them.  They can be very powerful when it comes to conveying an idea or concept.  But they are less dense in terms of information content, so they are more time consuming to use.  And don't take the place of a written reference.

I also like to see videos and PDF's that demonstrate a whole range of things:  What's different/changed? How to do XYZ?  Making this Widget.  Sometimes I don't know what I don't know.  Video are great for that.

All great stuff, and when I sit down to try some of the ideas and can't remember a detail, my favorite thing to do is to try and find it in the middle of a 10 min video.  No, just kidding.  I'll take the 10 sec it takes to just look it up in a ... reference.

An Example from a question I posted on these forms relating to what the color of tool paths meant.  It took 3 postings from 3 different autodesk folks to get a definition for all of the colors. (same problem with color meanings in sketch BTW).  I haden't even noticed that some of the lines were yellow, and some where gold. Go figure.

So I think the take away of this rant post, (you said be frank) is that every type of media presentation has the potential to be useful, but the help/reference is what ties it all together.

[TrippyLighting]

I very much agree with what laughincreek said. I believe the video where you explain a better way of modeling the slingshot was excellent because it showed some of the concepts in action on an actual example. Getting started with Fusion is very easy because ist is reallt very intuitive but some of the finer points are somewhat hidden and it's great to see those explained in the context of a particular project/problem.

The reference helps if you know what a tool does but don't rememner all the details involved in using it. For example yesterday a user asked if he be able to make a ot with splines. I had not done a loft before so it took a look at the online reference to figure out what all the menu points meant exactly. 

Nowadays a good online ressource can combine a reference manual and videos of how to apply the tool and how it can be used to solve a particular problem in very helpful and engaging ways. Sometimes it does not take a full screencast but the little animated gifs that some users have posted are very suitable to aid a written explanation.

[dunderhead]

I'm with you guys (laughingcreek, trippylightning). The current manual greets you often with almost insultingly bland information. 

The lack of a concise and curated go to source makes learning Fusion 360 difficult (for T-splines: very difficult) despite the general good taste and sense that have gone into this amazing product.  

For the Fusion 360 reference, I dream about someone in Autodesk issuing an edict banning videos longer than 5 seconds!  (The videos work great for tutuorials and for discussing complex issues.) Combine a video ban in the manuals with an incentive for putting all the friendly advice by autodeskers in these columns into that manual.  Imagine so much talent be put to work!

- dh