need tips to avoid laggy tsplines when sketching organic shapes

[smcarty]

I'm new to fusion 360 but have been using it for 3d printing some small designs. When the designs are based on sketches comprised primarily of circles/rectangles/squares, things go smoothly. (I'm really loving fusion 360.)

Today I've been working on an organic sun/flower shape using tsplines sketch and the experience has been frustrating.

Moving the tspline points to adjust curves to lay exactly where I want them (matching a handdrawn design on an inserted canvas) is a laggy mess. (I try to slightly adjust point, it skews across screen. I try to drop the point in place but the point is not dropped and is 'stuck' to the cursor. Right clicking to get menu and then click ok pushes the point off to the right of where you want it. etc.)

I've followed the suggestion on this thread to reduce effects and optimize performance: https://forums.autodesk.com/t5/design-validate-document/sketching-lag/td-p/6053720?nobounce but nothing changes. (Closing and restarting fusion 360 seems moderately helpful, deleting everything seems to help too, except then I have to start over.)

I've noticed that the performance drops almost instantly upon my first addition an extra point on any line segment.

Is this a bug or is there, perhaps a limitation on the number of points on a tspline that Fusion 360 can handle given?  

Can performance be helped by separating one design into multiple sketches?

Does separating designs into multiple sketches cause other problems? 

I have noted that even though the original organic tspline shape was drawn all in one big closed loop (with petals because sun/flower sort of pattern), when I right click a line segment between points only a portion of the entire shape highlights... also there is a warning message about "compute failed, some sketch curves cannot be converted to profile edges" but I'm having issues locating the actual location of the problem since the line segments are usually about 5-10+ inches long with anywhere from 3-10 petals drawn.

Thanks for any assistance you can offer.

[TrippyLighting]

If you have a sketch of what you want to model with T-Splines we can probably offer better advice. At the moment I am not quite sure what you are trying to achieve with sketching.

[smcarty]

I deleted what I was working on yesterday (which was more stylized)... the image above is something I sketched from a google image to show you the issue.

In this instance, the one tspline point that is arcing upwards out of pattern is "stuck" to the cursor and cannot be dropped back into a alignment. There are moments (15-30 seconds) of lag when I attempt to move any point. The lag gets worse if I add any more points along the line.

I'm new to fusion 360 but it has been great for use with my cnc machine when comes to making prototypes for various costuming props. The sun/flower patterns were going to be a small set of oversized coasters for a friend. So cylinders with a 4.5 inch diameter and perhaps .33 inch depth with some details worked on the top.  Fusion360 has been working great for anything with predetermined shapes (squares, circles, cylinders, straight lines, rectangles), but as soon as I get into something as asymmetric, organic, and detailed like a flower/sun pattern... the tspline points become an exercise in tedium to click and drag to the proper locations. I feel as if I'm overlooking something simple that can be done to make this process more effective. It shouldn't take 4 hours to edit 15 points along a sketch which takes me less than 2 minutes to draw.

[TrippyLighting]

The curves you show in your screenshot are not T-Splines but splines. That is big difference!

[smcarty]

You are correct. And I have no idea why I've been doing conflating those two words.

So does anyone have an idea on how to avoid laggy spline point editing?

I've built much more complicated items from geometric and symmetrical designs and lots of constraints with no issues but a design like this is problematic.

[jeff_strater · Accepted solution]

I think the problem here is that it appears that you have one large spline in this sketch.  Have you tried modeling this as a set of smaller splines?  My suspicion is that your single large spline is causing the lag.  So, that would be my first recommendation.

Interesting enough:  I have just recently created a design somewhat similar to this, as a way to learn CNC basics:

I created this using, ironically, TSplines, using a technique that I love, that I learned here:  https://knowledge.autodesk.com/support/fusion-360/learn-explore/caas/screencast/Main/Details/bfd1333...

You can see in the above image the splines I used as the starting point for the TSpline pipe forms.  

I know that's not the question you asked, but thought you might find it interesting anyway...

Jeff

[smcarty]

Thanks for the tip and the link! I'll retry my design with smaller parts tomorrow. (I've been hesitating to use smaller parts to make the design on a single sketch because, in the past, smaller parts has resulted in duplicated lines which has caused a lot of weird extrusion errors.)

Is it normal for a design like that (complicated, not geometric/symmetrical, a lot of points) to be laggy? Or would that be a problem with anything that has a lot of points?

(My comp isn't a beast or anything just a decent gaming desktop but this is the first time I've experienced lag of any sort designing stuff for the cnc machine.)

Thanks again!

[jeff_strater]

Hi @smcarty,

Yes, basically, what you suspect is true:  At some point, if a spline curve has too many fit points, the performance degrades a lot.  I have another design I did for CNC practice that illustrates the point:

At the beginning, I did try to model this as one gigantic spline.  But, as you experienced, each additional fit point I added made the performance worse, until even creating the spline was too much.  So I broke it into separate splines, and this seemed to work much better.

Here is a screencast that looks at this design:

And yes, I did model this upside down .  By the time I realized that, I had also realized that our CNC machine could not cut it anyway, because we did not have a small-enough tool, so I never went back to fix the model.

Jeff

[smcarty]

I know I tried hooking multiple splines together at one point and editing placement was still very laggy. However, I don't think I used tangent constraint between the splines.

I'll fool around some more and see what I can figure out. I may just do some individual petals/segments around a semicircle.

Thanks again for the assist!

[smcarty]

Tried this again using your tips and had the project finished within an hour. (Other than the machining.)

Thanks for the help!