A Question about Base Features
This little section in the documentation explains the purpose of a base feature.
In s\essence it allows you to model geometry in an isolated direct modeling environment within a design that does have a timeline.
I just tried it pouted cannot reproduce what you describe. Can you share your design or create a screencast ?
You need to create the sphere within the base feature, so after you create the base feature.
I'd have refer to @jeff_strater for the ultimate answer, but I would say that this is by design. It makes little sense to try to modify geometry outside of the base feature from within the base feature.
If you want to modify that geometry then simply finish the base feature.
If you have a specific use case where you feel that this would be useful, then please post it. It would help to support the case.
If you copy the body before creating a base feature you can paste it into the base feature after it's active or you could use boundary fill to create a copy from within the base feature. The other option is convert to DM feature to convert a body to a base feature but either way you are not going to be able to edit a body that still has features in the timeline from inside a base feature.
Mark
Mark Hughes
Owner, Hughes Tooling
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I can explain a bit about the nature of Base Feature, its limitations, and its intended usage.
Fusion supports two very different design types: Parametric Design (history-based), and Direct Modeling Design (non-history-based). Parametric designs have a timeline across the bottom, which is a linear series of features. These designs allow you to go back in time, edit earlier features, and have the model recompute. Parametric modeling is powerful, but also complex to use. Direct models, on the other hand, have no feature timeline (there is no connection between a sketch and an extrude in a direct model). They are more flexible, but also limited in what you can do, if you want to edit the design later. More info here: direct vs parametric
Rather than have these as two distinct and non-intersecting worlds, we decided to try to create a more hybrid design type: Base Feature allows you to embed Direct Modeling bodies within a Parametric design. Think of a Base Feature as being similar to a Form/Sculpt feature - it's a self-contained "island of direct modeling" within the larger design timeline of the parametric design. When you edit a Base Feature, your design scope is limited to bodies (and sketches and work features) that are inside this island. It's very modal. Edit the Base Feature, do some direct modeling there, then exit back to your main parametric design scope.
Why is the design scope in Base Feature limited to the objects owned by that Base Feature? Because it has to be. To use @nnikbin's example:
1- Create > Sphere
2- Create > Create Base Feature
3- Modify > Split Body (want to split the Sphere)
Remember, while editing a Base Feature, no timeline entries are created, so if Fusion allowed this Split Body to occur on a parametric body, any update to features before the Base Feature would cause that operation to be ignored. To carry this example forward, say this Split was allowed. After exiting the Base Feature mode, you would have two hemispherical bodies. Now, say you filleted the edge of only one of those hemispheres, which creates a Fillet feature in the Timeline. So far, so good. But, remember, the Split Body is not a feature in the Timeline. It was created during a Base Feature (direct modeling) edit, so was not captured. Now, say you go back and edit the Sphere in step 1 to be larger. The Sphere recalculates, and is now bigger. But, the Split was not captured, so it never happens, the edge that you filleted no longer exists, and fails.
Hope this helps clarify the behavior, at least somewhat
Jeff
Jeff Strater
Engineering Director
I'll start with the last question first: "Also, is there a way to tell which objects belong to which BF without entering the BF?". That answer, unfortunately, is "no". This is one bad thing about base features in Fusion. It's even worse - you cannot tell which sketches and work geometry are owned by a base feature vs being parametric. It is a source of confusion, definitely.
And, yes, I can verify the behavior you are describing: If you edit base feature N, then any sketches owned by base features 1 - N-1 seem to be editable. Any sketches from N+1 or beyond are not editable, simply because they have been rolled out by the base feature edit. I would say that is a bug, not intended behavior. At least, I cannot remember, or come up with a reason why this is desirable.
The truth is: Not too many people use base feature. I think it has its place, but it is definitely not widely used. So, for better or worse, I don't expect these relatively minor issues to get addressed any time soon.
Jeff Strater
Engineering Director
