CAD Forum

Hello everyone. I've been trying to solve this puzzle for a while. I am making a model similar to a game controller. What I need to do now is create a smooth transition between the three surfaces and two sketches that are shown in the picture. The result should be as on the reference photo of a handmade prototype. I found two ways to make something similar to what I wanted, but the result doesn't allow me to impose tangency so the surface has noticable creases. The first way would be to fill the area with two boundary surfaces (example 1). The second way - to create interstection curves between a plane and the two surfaces and draw a spline tangent to the curves. But then I can't figure out how to smoothly fill the lower gap (example 2). Could anyone give a hint on how to build this surface in a better way?

Use a Fill surface. That should get you where you want to go, assuming your existing surfaces are consistent with themselves. You may need to set up reference surfaces at the sketches for tangency direction, but you'd need to make sure that the reference surfaces are also consistent with the rest of the surfaces.

Many times when features like this with tangency or curvature specified all the way around fail, it is because the adjacent input surfaces are not tangent with one another.

Divide such that you have two 4-sided regions.
Even better if you divide to match part topology. Fill is a last-ditch gambit to be avoided.

matt wrote: ↑Mon Jan 10, 2022 9:13 am Use a Fill surface. That should get you where you want to go, assuming your existing surfaces are consistent with themselves. You may need to set up reference surfaces at the sketches for tangency direction, but you'd need to make sure that the reference surfaces are also consistent with the rest of the surfaces.

Many times when features like this with tangency or curvature specified all the way around fail, it is because the adjacent input surfaces are not tangent with one another.

Thank you! Don't know how I managed to overlook the fill command, it gave me a perfectly smooth result.

HerrTick wrote: ↑Mon Jan 10, 2022 9:34 am Divide such that you have two 4-sided regions.

image.png

Even better if you divide to match part topology.
image.png

Fill is a last-ditch gambit to be avoided.

Thanks! Will try it out! Could you explain why should the fill command be avoided? It doesn't give much flexibility, but for me it did the job.

GrayFurStripe wrote: ↑Tue Jan 11, 2022 10:36 am Thanks! Will try it out! Could you explain why should the fill command be avoided? It doesn't give much flexibility, but for me it did the job.

Splitting the job into multiple features just adds additional sources of error. Making additional acute angles is also often problematic. Some people don't like that the Fill doesn't match the existing UV flow of surrounding patches, but I'm ok with that as long as it gets the tangency correct without puckers or other artifacts.

You can use guide curves and reference surfaces to help you gain control with the Fill. Check these out:

https://episodes.dezignstuff.com/blog/t ... l-surface/
https://episodes.dezignstuff.com/blog/t ... y-or-loft/

Splitting the job into multiple features just adds additional sources of error.

Only if you do it wrong. The key to doing things well is doing them right.

Thanks! Will try it out! Could you explain why should the fill command be avoided? It doesn't give much flexibility, but for me it did the job.

First, resorting to fill often occurs because the designer has not carefully considered the situation he has created. Take a few steps back and see how you got from here to there.

Good CAD modelling takes a parts topology into account. Features that work harmoniously with a part's topology are far less likely to fail than those that don't. Even if you have more features, they will be more stable, and easier to repair if they do fail.

B-surfaces work on a mathematical 2-ish-dimensional U-V grid (analogous to 2D X-Y grid). If you model in a fashion that is more in step with the way a modelling kernel creates surfaces, you are far less likely to generate part-killing corruption. Fill surfaces of five or more sides are throwing a lot of unseen sweat into the mix over which the user has no control.

Final thought:
I don't fret much about feature count. Mouse clicks are cheap; use all you like and feed the leftovers to the cat. What really counts is model integrity and the speed at which a project gets done. Nothing slows a project down like repairing models unravelling because someone saved a few mouse clicks.

Fill can be a pain when shelling downstream. I spent several hours yesterday trying to shell out a plastic moulding that had a perfectly reasonable-looking and generous filled surface fail to offset under anything other than tiny wall thicknesses. SW would either kick up a fuss over failing faces OR do the weird intersecting faces thing which leaves a faceted inner shell and geometry errors.

@Cadmonkeychris not sure if you've taken a look at the Power Shell Add-in for Solidworks, but I can definitely say that it shells models SO much better than what the native shell tool does inside of Solidworks.

https://www.npowersoftware.com/NewPower ... rview.html

Ooh that's nice. I presume it requires others have to purchase the same software if they need to edit after I have released files (or if we are working together)?

I might get a copy of that if we don't move to another package.

Thanks.