Hi everyone, today I was practicing the Fillet Surface command in Rhino 5 and ran into a problem. I’m trying to create a fillet with a radius of R=3, but the area marked in red doesn’t work. I want the transition to look smoother and more natural, but I haven’t figured out how to achieve it yet.
In Rhino8 the command to do this is FilletSrfCrv.
In Rhino5 it is a test command → testfilletsrfcrv. To use the command in Rhino5 the first thing you have to do is set the radius: that is called the thickness option. Then you select the surface and then the curve. The curve is the edge where the main fillet ends (the red curves in the file). Don’t use the extend option when you make the main fillet. The testfilletsrfcrv command makes unnecessarily dense surfaces so I used RebuildUV to simplify those surfaces.
Also, I started by changing the tolerance to .001. Too tight tolerance makes very dense surfaces.
Filletx.3dm (397.7 KB)
Sorry Jim, but I still can’t do as you instructed at testfilletsrfcrv. Can you give me the Video? I’m really sorry because for a newbie like me it’s really difficult 
You can achieve it with FilletEdge, and for your reference.
testfilletsrfcrv will make a fillet of a given size between a surface and a curve.
The user interface (UI) for this command in Rhino5 is horrible and the Rhino5 test command has lots of bugs, but really the steps are very simple once you understand how to navigate the minefield.
Use this file and follow the instructions below. testfilletsrfcrv.3dm (298.8 KB)
There are 3 easy steps after you start testfilletsrfcrv command:
Type the number 3 in the command line (this sets the radius to 3)
select the pink surface by clicking on it (just like you would for filletsrf )
select the red curve by clicking on it
It will take a second or two and then the fillet you ask for will appear.
Don’t be sorry, Even people who work at Mcneel can’t get this test command to work. It is very difficult. And it took about 10 years before they made this command produce geometry that is usable with a UI that is understandable.
So learning to use testfilletsrfcrv is not the end of the story. If you try to use the geometry that testfilletsrfcrv produces you will discover that when you try to trim the pink surface, the trim command will fail. This is because the surface that testfilletsrfcrv produces has so many knots that are packed so tightly together that the surface can’t be used for any subsequent geometry operations. That is where the rebuildUV command comes in. After you fix the defective fillet that testfilletsrfcrv makes with rebuildUV you will be able to trim and join all the surfaces.
Simply make the vertical surface longer in the z-direction (downwards), then fillet R3, then cut it off at the original height (and cut the fillet also). This way, you get your R3 “cut off radius”, as it’s known in industrial design.
This proceedure, in contrast to what Jim described, moves the lower edge in where the height is insufficient for a full fillet.
Your method results in a gap with the original edge (red in the image below) where the fillet is cut back. The gap may or may not be acceptable depending on how the result will be used.
Fillet DC01.3dm (3.5 MB)
Well, the poster can’t have it all. If he wants a 3 mm radius fillet throughout, it will have to end as a cut-off radius fillet, and he’ll jump off of the top view outline. Alternatively, he’d use a variable radius fillet, starting at 3 mm, then petering out to something tiny for “lack of meat” on the side surface. But then, that’s no longer a 3 mm radius fillet along the edge.
No, because it is not a 3mm radius anymore.
It may be the best solution, but you cannot “have it all”
The purpose of FilletSrfCrv command is to create a rolling ball fillet that goes between a surface and a curve. In this case that will preserve the top view outline.
Its not that your method is incorrect . There are situations to use that method. It all depends on what shape the user wants.
Here is an example FilletSrfCrv.3dm (230.5 KB)
I think you better check that statement. The radius of the fillet will be precisely 3mm if that is what the user requests.
I checked that statement and you are, of course, right.
Thanks JIM, I got it. I was wondering why the testfilletsrfcrv command doesn’t show up on the Command bar like the other commands. I copied and pasted it and it worked.
I will introduce it to my friends and teachers tomorrow morning. In my area, very few people can use this software, so I appreciate your detailed explanation.
Also, I will introduce @jessesn and @Lagom method because maybe it will be useful at some point.
Thanks everyone.
