Hosting Linear Pendant at an Angle

[levitd]

I'm currently working on a schematic lighting design where I would like to be able to host linear pendant fixtures at an angle with respect the the ceiling. Essentially, I'm looking for something where I can specify the elevation of each end of the fixture in the type properties, and it will update appropriately. Does anyone know of a family like this, or any tips on creating one?

Thanks

[CoreyDaun]

Hello and welcome to the forums!

This can probably be done a number of ways depending on what you need:

- How are you intending to show the fixture in Plan View? Were you aiming to show the actual geometry of the fixture, or just a Symbolic Line representation?

- How details will the geometry of this Family be? It would perhaps be best to model the body of the Fixture separately and load it into a host Family which will control its angle.

- Even with normal suspended fixtures, it is really no very possible to set it up to specify the elevation from the floor unless the Family is Level-Based, in lieu of hosting to the ceiling face. In the case of the latter, you could specify the suspension length for each side.

- As a tip, I created something like this a while ago, and I included Invisible Lines to indicate which side was which when adjusting the angles from a Plan View. These indicator lines appeared only when the element was selected.

[levitd]

Thanks for the quick reply.

- As far as showing the fixture in plan, I'm not too concerned with how it looks. In all likelihood, it will just show the footprint of the fixture, and we'll use notes/schedules to specify the pendant length at each end.

- The model doesn't need to be very detailed at all. In fact, the fixture itself is pretty minimalist, it will likely be 4-12 ft long, 6" high, and 2" wide with a simple acrylic diffuser, so it will just look like an extruded rectangle. I hadn't thought of making the fixture itself as a family and then loading it into another family that controls the angle... that's where I've run into problems trying to make the family, is trying to get all the angles to work out right.

- My mistake on my wording, I don't really need to specify the elevation from the floor. Specifying pendant length from the ceiling is totally fine.

- The invisible lines are a good idea. I'll have to look into that.

So, how would you go about the solution you mentioned above? (fixture family hosted in a angle-setting family) Would you create the fixture family with simple parameters (length, width, height, etc.) and then load it into a family that solely dictates the angle from the hosting plane?

I'm fairly new at creating/changing families, so any suggestions are helpful.

Thanks again!

[CoreyDaun]

In this case, the solution should be pretty easy. Since you're going to represent the fixture body with a single Extrusion, you won't need a Nested Family. You can use a Sweep Extrusion and use Reference Planes to control the angle. I'll briefly explain my steps for a simple solution, starting with a blank Lighting Fixture family.

1.  Create two Reference Planes; one to determine the height of each side of the fixture, create a Parameter for each, and then constrain with a Dimensional Constraint.

2.  Create two vertical Reference Planes if you want the center of the Fixture as the Base Point or one Reference Plane if you want one end to be the Base Point.

3.  Create the Parameters to control the Fixture Body's Length, and Height and Width (if desired). Now, the horizontal span of the fixture will not be equal to the Fixture's specified Length if it is hung at an angle. Create another Length Parameter to constrain the horizontal Length. Use the formula:

= sqrt(FixtureLength ^ 2 - abs(SuspLength1 - SuspLength2) ^ 2)      (using pythagorean theorem)

4.  Create a Sweep Extrusion, and draw the Path between the two appropriate intersections of Reference Planes. They should constrain themselves. As a tip, if you are ever drawing a Path at an angle, draw the first segment as a small, level line so it will be easier to draw the Profile. When completed, go back and delete the extraneous Path line.

5.  Create the Sweep's Profile and apply the Fixture's Dimensional Parameters as Constraints, if desired.

6. Model the cables, if desired. Models Lines work well for simple cables.

Again, this is very brief so don't hesitate to ask questions. Attached is a sample Family file (Revit 2013). Try creating your own - don't just use the example file!

[CoreyDaun]

As an edit to my previous post, use the formula below instead:

= sqrt(abs(FixtureLength ^ 2 - (SuspLength1 - SuspLength2) ^ 2))

The "abs" function means Absolute Value. Since the SuspLenths are squared, it's impossible to have a negative value there (which would produce an error). Instead, the "abs" should apply to the entire equation prior to the Square Root function in order to avoid a potentially erroneous negative value (since there is no square root of a negative number).

[levitd]

I think I've gotten everything up to making the sweep. So when I create the sweep's path, I should pick the intersection of the SuspLength plane and the two vertical planes defining Horizontal Length (the calculated value)? Is that correct?

Once I've created the sweep path and am editing the profile, how do I actually constrain the dimensions (height/width) to parameters? I have to have already created reference planes w/dimension constraints for each of those, and then just draw the profile as a rectangular intersection of those four planes (top, bottom, left, right-sides of fixture), right? For some reason, I can't get that to work for me. 

I think I could get it if I didn't want to be able to change the width/height, as I could just model it as the exact fixture I'll be using, but obviously it would be better if I could re-use this family. I may just use the one you uploaded until I can get this figured out, if you don't mind!

Thanks,

Levi

[CoreyDaun · Accepted solution]

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levitd wrote:

"I think I've gotten everything up to making the sweep. So when I create the sweep's path, I should pick the intersection of the SuspLength plane and the two vertical planes defining Horizontal Length (the calculated value)? Is that correct?"

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That's correct. By drawing the Line from one intersection of Reference Planes to the next, it should automatically associate with them.

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levitd wrote:

"Once I've created the sweep path and am editing the profile, how do I actually constrain the dimensions (height/width) to parameters? I have to have already created reference planes w/dimension constraints for each of those, and then just draw the profile as a rectangular intersection of those four planes (top, bottom, left, right-sides of fixture), right? For some reason, I can't get that to work for me."

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You do not necessarily need Reference Planes for each and every constraint in a Family; you can instead just apply Dimensional Constraints to the Profile's Sketch Lines while in Sketch Mode. Open the sample Family and edit the Profile and you'll see my "internal" constraints within the sketch. It will appear kinda wonky if it's at an angle, so level out the fixture before looking.

This is why I typically draw a small section of "level" Sketch Path (as described in my previous post); for the purposes of creating and managing the Profile Sketch. OR, you can simple open the Family Types dialog while in Sketch Mode and even out the fixture.

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levitd wrote:

"I think I could get it if I didn't want to be able to change the width/height, as I could just model it as the exact fixture I'll be using, but obviously it would be better if I could re-use this family. I may just use the one you uploaded until I can get this figured out, if you don't mind!"

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I don't mind, but it sounds like you're close!

[levitd]

That's great, got it figured out now! Now to get the light source to move and stay parrellel with the bottom of the fixture! But I'll mess around with that.. Thanks a ton for the help. Now I just need to think about all those steps a bit more and make sure I actually know why we did them...

Anyway, thanks! Very helpful instructions.

-Levi