Hello Michael,

Sorry to keep bothering you with the same basic issues.

In order to blend the one fillet radius into another I'm going to go about it with two different methods to learn both. Here is the first method and the weird problem I'm getting.

The basic process is that I took the body shape and filleted it with both radii.

I swept the blend curves, trimmed the small piece that will have multiple radii.

Then I was going to weld (union) them together.

Here are the two blocks I built.




I then overlayed them like this and performed a UNION to weld them together.




Unfortunately I got some weird results on one side. I got a zigzag edge after I unioned the pieces. I couldn't see it in the before blocks.





Here are some closeups of the zigzag and a closeup of the geometry that looks like it may be causing the problems. A mismatch of the pieces perhaps?









Unfortunately, I don't know how the zigzag was created since I copied curves from both blocks to make the trim curve. I'm guessing the filleted process may have moved something out of alignment.

Any guesses suggestions.

Thanks as always.

Jeff

Hi Jeff, did you possibly post the wrong model file?

The one that was attached to your model file does not seem to be the one in your screenshots above with the overlapping fillet surface areas, the one you attached seems to be 2 blocks stacked on top of each other:



Is the one that you're showing in the screenshots above with 2 fillet-like pieces overlapping right on top of each other from some other model that you meant to post?

But that kind of zig-zag intersection that you show there can happen if you've got 2 surfaces that are kind of barely skimming through each other in such a way that one is kind of only partially submerged in the other. That kind of situation tends to result in zig-zaggy intersections like that - if you've got something that kind of bubbles in and out of another thing that's actually what the physical intersection between them will tend to look like.

In situations like that you may want to trim the surface to what you know are common curves (possibly edges) rather than trying to intersect the surfaces directly which is what the booleans will try to do.

If you could post the model that you show in your screenshots above that would probably help me to give you some better advice.

A couple of things that I did notice about the one that you did post though is that you've got some planar areas that are diced up into some small plane fragments, like this here:



That's generally something that you want to avoid - there are some kinds of operations that will actually get confused with that, and it's a more complex model (more faces and edges) than is needed. So you usually want to just have one big plane in situations like that instead of a lot of little co-planar fragments.

You can fix those up by selecting all 3 of those top fragments and deleting them, leaving an open hole there like this:



Then select that object which now has a large planar opening at its top and run the Construct > Planar command to fill it in with a planar surface to get this result:




The Construct > Planar command can work in 2 different ways - if you have curves selected it will build a planar surface through those curves. If you have a surface object that has planar openings in it, it will build a planar surface and join it into those areas to make a cap there.


Then the other thing that I did notice about the model that you posted is that the ends of your fillet pieces here do not seem to have a very nice regular shape to them, there seems to be a small sudden swoop right near the end:






So there's something like a kind of sudden bulge or swoop near the end of that surface there, that may explain why it results in a zig-zag type thing if you are intersecting it with a fully regular-shaped fillet piece.

But try using the Trim command to cut the piece that is giving you the zig-zag result instead of using the boolean - if you have a curve you can trim your surface to rather than a grazing surface it can give you a better result.

For more advanced kinds of surface modeling like this kind of a project, where you're building some surfaces of your object individually, you tend to use Trim for that kind of a thing to work at the surface level as well - booleans are more focused on combining together solids and may have difficulty in situations where you're better of trimming with a curve rather than doing surface/surface intersections.

- Michael

Hi Jeff,
I think this is the result in the area you are talking about:



I only did the one side but this should show you what to do...

What you need to do is to create a copy of the piece that you want there and do a "boolean difference" with the copy.. Then you can boolean add the piece in to acheive the variable...

Note: When i did the boolean difference, I zoomed into the area and deleted a little fragment that was left over to clean it up a bit...

I've included a file with just the piece there in it to be sure we are talking about the same thing..

Hello Michael, Burr,

Thanks as always for your suggestions and advice...

My comments...

1. The model has a lot of the pieces hidden. I guess I saved it with only the two pieces showing.

2. "In situations like that you may want to trim the surface to what you know are common curves (possibly edges) rather than trying to intersect the surfaces directly which is what the booleans will try to do."

"But try using the Trim command to cut the piece that is giving you the zig-zag result instead of using the boolean - if you have a curve you can trim your surface to rather than a grazing surface it can give you a better result."

>> I guess I'm a little confused with what I should do. I think I did what you suggested. I made a set of 3 lines that that I used to cut up both solids and then tried to UNION them together. The lines were snapped to edge of the swept surface.

I used a boolean difference to cut up the solid. Are you saying that I should use trim instead of DIFF when I slice up solid that I'm going to glue back to other pieces?

3. "A couple of things that I did notice about the one that you did post though is that you've got some planar areas that are diced up into some small plane fragments, like this here:"

>>This happened because I took the neck pocket shape and cut and extruded it to use it to "rout" out the neck pocket area. I'll clean it up if it causes issues.

4. "Then the other thing that I did notice about the model that you posted is that the ends of your fillet pieces here do not seem to have a very nice regular shape to them, there seems to be a small sudden swoop right near the end:"

>> I saw this too, but wasn't sure why I got this or how to fix it. I "borrowed" curves from the two filleted bodies and swept a curve between the two radii and along a curve I extracted from one of the bodies.

5. "For more advanced kinds of surface modeling like this kind of a project, where you're building some surfaces of your object individually, you tend to use Trim for that kind of a thing to work at the surface level as well - booleans are more focused on combining together solids and may have difficulty in situations where you're better of trimming with a curve rather than doing surface/surface intersections."

>> Is this referring to #2 where I should use the "trim" command instead of Boolean DIFF?

I'm using a lot of time trying to figure the best way to model things, but I do appreciate everyone's guidance. I think I'm saving a lot of time overall.

I was going to try another approach to the whole fillet blend situation. I was going to try and use those swept curves and "glue" them on some solids and then patch up the holes. I guess I should learn both methods since in some cases one would work better than another.

I'll study Burr's post before I comment on it.

Thanks guys.

Jeff

Hi Jeff, well with my previous comments I was kind of confused about what you were referring to originally since I didn't see anything similar to your screenshots when I opened up your model file.

In those screenshots I just saw what looked like 2 fillet pieces kind of directly overlapping on top of each other in the same space - if one of those fillets was supposed to be cut by the other one in the final model, then instead of using boolean union to do that kind of cutting it could be better to trim the fillet pieces with a curve - I was presuming that you were trying to kind of splice together 2 models that had some overlapping surface area in them? That's what it looked like from your original screenshots anyway.

- Michael

Hi Jeff, so I'm having some difficulty following along with your steps.

In your first post in this thread here, you posted this:




But even with showing all the hidden objects in the file you posted, I can't seem to find those objects - the closest things seem to be these?




Is it possible for you to post the model file that matches the screenshots that you posted? That would make it much more feasible for me to attempt to follow along with the steps that you are talking about in your question and to try and understand what you were doing.

When I can't get at the actual 3DM model file that goes along with your screenshots, it makes it much more difficult for me to understand, sorry.

So when I was talking about surface trimming, what I meant was something more along the lines of taking this long fillet surface here:



And trimming it by the edge of this smaller custom sweep piece that you made here:




Instead of doing a boolean to combine things together, you can also work with things at the surface level, trimming away parts of surfaces that you don't want to keep and then using the Edit > Join command to glue the surface pieces together back into a solid.

I guess you are doing something more like trimming each piece with a common line?

> Is this referring to #2 where I should use the "trim" command
> instead of Boolean DIFF?

It's more like - if you want to build a custom surface by a sweep for one piece of the model, to then splice this new surface into place you may want to use the Trim command to cut the original long fillet at the place where your custom piece starts so that will make an empty area for it to fill in.

That's a kind of surface modeling workflow where you can work with individual surfaces for a while instead of doing booleans. To do the surface modeling type workflow you generally use the Trim command to cut the surfaces up instead of booleans - booleans are more for operating on solids.


I am still pretty confused about your question though - I can't find the models to match your screenshots and I have not actually even seen where the zig-zag is located yet. So that's making it difficult for me to give you the best advice since I don't fully understand your construction method yet.

- Michael