Generic Model behaviour as nested family
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I posted this so maybe that would help other users. I googled the issue but did not find much except a few mentions here and there.
Recently I tried to create a complex window family. I consider myself as quite advanced family creator but Revit still amazes me sometimes. It's like playing chess with it. You make a move but it would immediately hit back.
This time I tried to join two nested families together. Don't ask me why, it's a long story. It's tricky enough itself but if you try to do this inside a family of another category, strange things will happen.
First, only few categories allow joining nested families. These categories are:
- Columns
- Generic Models
- Structural Columns
- Structural Connections
- Structural Foundations
- Structural Framing
No window family. So I did a chess-move. I turned the nested family (of window category) to a generic model family. I reloaded the family and now I was able to join two generic model families together. After doing that I changed their categories back to window category. The joining condition remained. I was glad.
At least for 30 seconds.
Util I loaded it into my test project and noticed that the graphics is wrong. I struggled with it almost the whole day and finally did some tests to clear things out.
I created three new families from Generic Model.rft template (as it is the cleanest one). I changed the category of one of them to window category and renamed it "Window". Then I renamed the remaining two as "Nested1" and "Nested2". I created some geometry inside them and then loaded them to window family.
First, nested families of different categories do not behave the way you expect them to. If the nested family inside my window family is of Columns, Structural Columns, Structural Framing or Structural Foundations category, its graphics match as if to load the same family directly to a project. However, when I chose it to be Generic Models or Structural Connections category, the nested family did not cut in plan. So even though both Generic Models and Windows categories are cuttable, this changes if you put GM to W family. So that means its not the behaviour of either category.
When I tried to figure out why it is not cut in plan I noticed another interesting thing. If Generic Model family is nested to Window family, its graphics in plan view is controlled by projected lines of Window category. If the geometry inside the Generic Model family has a subcategory, then its graphics in plan view is controlled by projected lines of this subcategory. When you turn off this subcategory the geometry disappears. When you turn off Generic Model parent category, geometry stays visible.
Now, that's confusing enough, but then I tried to use Join Geometry tool. That made things even more strange. So in conclusion this is what I found out.
- Generic Model nested in Window family - lines are controlled by projected lines of Window category
- If you use Join Geometry tool to join two such nested instances together - lines are controlled by projected lines of Generic Models category.
- Two nested instances joined, one of them deleted - the one remaining still maintains its behaviour like it's being joined. You cannot use unjoin geometry after that
- If geometry has sub-category - lines are controlled by projected lines of that sub-category of Generic Models category.
- Two nested generic model instances joined, then their category is changed to Windows category - lines are controlled by projected lines of Windows category
So in other words:
Generic Models are always projected in plan view if nested to a window family. By the way, the family environment tries to convice you that it's cut in plan, but will be not.
Nested family category switches depending on how you created the geometry and whether you used Join Geometry tool.
If you use Join Geometry tool, non-shared family instances will ALWAYS lose their ability to be shown cut in plan. That is also true with other categories like Structural Columns for example, which otherwise are able to be shown cut in plan when nested to a window family.
If a nested family is shared, it maintains the correct behaviour of its category no matter what the parent family category is or whether the instance is joined to something or not.
Join Geometry tool do not change the nested Generic Model behaviour if parent family is also Generic Model family.
So I did the last test. I changed the parent family to Generic Model and nested family to Window. We know that window family takes its cut plane from the family and the condition whether an instance is cut from the project. However, nested window inside Generic Model behaves like generic model - cut plane of this window family does not have any effect.
Finally I checked the graphics. Projected lines of this nested family were controlled by Window category and cut lines by Generic Model category.
Now I am totally confused.
