Curves workbench weirdness?

[Chris_G]

Blend Surface uses some Blend Curves under the hood to build the surface.
The number of BlendCurves used is set by the "Samples" property (20, by default).

A blend curve uses a scale value at each of its extremities, to determine its shape.
In order to reduce computation time, these scale values are not computed for the 20 Sample curves.
Instead, they are computed for a lower number of "Scale Samples" (3, by default), and interpolated

But this default value of 3 is obviously too low. I will raise it to 6.

Now of course the thickness tool fails on the solid because "BRep_API: command not done" and "Unknown OCC exception". But that's a different topic. Sigh.

Part Thickness is a very sensible operation that can fail quite often.
I had success with the round cap, but not with the other one.

[Cekuhnen]

Here is a usual Surfacing Technique to help the blend surfaces

NOTE: Think about NURBS as a plastic stick that always wants to straighten out

So to make blends the way we want we have to create curves to force the surface into


This fixes the Surface WB Filling command
This command has a guide rail option.

This curve is made by 3d blend curves based on curve projections onto / from the target surfaces

Screen Shot 2021-07-23 at 10.49.46 AM.png (71.28 KiB) Viewed 832 times

FreeCAD shows me the surface in a pretty rough state but when loaded into my other CAD app the edges pass G1 Tangency checks
There is some noise on the surface - particularly the smaller Surface Fill seems to have some inflection points.

Screen Shot 2021-07-23 at 10.46.43 AM.png (270.54 KiB) Viewed 832 times

Screen Shot 2021-07-23 at 10.46.51 AM.png (346.2 KiB) Viewed 832 times

Screen Shot 2021-07-23 at 10.48.41 AM.png (170.83 KiB) Viewed 832 times

[Cekuhnen]

Raise the number of Scale Samples from 3 to 6 or 7.
Then you can use all the visible faces to build a parametric solid.

very interesting post - the blend surfaces are even g1 to each other? pure luck/coincident in this model?
thats why i mixed blend surface and fill surface with g1 for all edges

[Cekuhnen]

Hey Chris_G

any idea why the curve WB blend surface deforms so much on one side?

Screen Shot 2021-07-23 at 11.56.47 AM.png (104.4 KiB) Viewed 805 times

Screen Shot 2021-07-23 at 11.56.56 AM.png (108.82 KiB) Viewed 805 times

.
.
.
Interesting is how also surface WB filling has that issue

Screen Shot 2021-07-23 at 12.20.46 PM.png (127.29 KiB) Viewed 799 times

[Vincent B]

Coons, as often, carry out a nice surface.

[Vincent B]

FreeCAD shows me the surface in a pretty rough state but when loaded into my other CAD app the edges pass G1 Tangency checks
There is some noise on the surface - particularly the smaller Surface Fill seems to have some inflection points.

Not too bad for a free software!

[Cekuhnen]

Not too bad for a free software!

Yeah it is slightly above TinkerCAD

I have the same approach on a previous page with the surface WB SurfaceFill using an internal curve to guide it.

I am confused why the curve WB BlendCurve also shows a similar issue

[Cekuhnen]

Not too bad for a free software!

He now added a Blend solid tool - super amazing !

[Olav]

Blend Surface uses some Blend Curves under the hood to build the surface.
The number of BlendCurves used is set by the "Samples" property (20, by default).

A blend curve uses a scale value at each of its extremities, to determine its shape.
In order to reduce computation time, these scale values are not computed for the 20 Sample curves.
Instead, they are computed for a lower number of "Scale Samples" (3, by default), and interpolated

But this default value of 3 is obviously too low. I will raise it to 6.

Thanks for the explanation. Most of this goes over my head I'm afraid, but I've really just started learning the Curves workbench last week or so after watching a video.

Do I understand correctly that you are the developer of this? Awesome work, I can already tell this is going to be very useful in some projects I have in mind.

So thanks again.

[Chris_G]

Do I understand correctly that you are the developer of this? Awesome work, I can already tell this is going to be very useful in some projects I have in mind.

Yes. But please keep in mind that the workbench should be considered experimental. Don't use it for any serious work.