Forums >> Revit Building >> Technical Support >> sloped ref planes and length constraints

jlights

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Joined: Tue, Dec 18, 2007
146 Posts

I'm trying to use a length parameter to control the suspension cable length of a fluorescent lighting fixture family. I have some geometry locked to planes that are parallel to the ceiling, and some locked to sloped planes (the angled glass diffusers).

Now I have apply a length parameter to the suspension cables which are perpendicular to the sloped planes (the cables are angled, not vertical). 

How do I get all the parallel and sloped planes to stay locked together as the cable length changes, so that the geometry all stays the correct shape?

To make matters more complicated, the endcaps are triangles with curved rather than flat sides, and these need to move with the fixture as well, but I have not found a way to constrain this kind of a shape to a reference plane. 

I've added a couple of screen grabs to show what I'm dealing with and what happens when I add the length parameter. 

Any ideas? Thanks in advance.

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jlights

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Joined: Tue, Dec 18, 2007
146 Posts

So here's the fixture I'm working on. It's drawn with an 18" nominal drop length and I would like to be able to use a length parameter (which I know how to set up) to change the drop length to 12" (these are the only 2 lengths I need). However, since the body of the fixture is compised of elements some of which are at an angle to the surface, and some of which are parallel to the surface, I can't construct a length parameter to tell all parts of the fixture at once where to be in relation to the surface. A parameter controlling a dimension that is perpendicular to the surface will only move planes parallel to that surface, and therefore distort the shape of some (angled) parts of the fixture. Likewise, a parameter controlling the sloped planes will only move the sloped planes and elements locked to them, and cause different distortions. Hope this makes sense.

I tried making the fixture body a nested family, hoping I could move it as a "block" in this manner, but it didn't work. I tried constraining the nested fixture body to a reference line but could not constrain it. 

FYI, the generic face-based family template is the template I MUST use for this project (no other template will be appropriate for what I am doing).

Any suggestions anyone might have would be welcome. Thanks!

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