Join Paul F. Aubin for an in-depth discussion in this video Understanding light fixture families, part of Revit: Rendering.
- In this movie I'd like to talk a little bit about light fixture families and dig a little bit deeper into the properties that a light fixture family has. Light fixture families are actually special in the sense that not only do they contain the geometry of the actual light fixture itself but they also contain a special object called a light source which casts light into our scenes when we generate renderings. So I'm in this interior scene here and because it's a perspective I'm going to notice one small problem with trying to edit the families is if you select any of the light sources here.
I've got these sconces on the walls or this freestanding desk lamp or these light fixtures up here in the ceiling the edit family button is not present. So unfortunately you can't get to edit family from a perspective view. But that's not that big of a deal. All you have to do is just go to another view that's orthographic and then you can edit family from there. So I've actually created a view here called cut away. This is just an axonometric set to a section view and we talked about how to build this in a previous movie. And now you can see that if I select any of the light sources I now have the presence of the edit family button.
So I'm going to select the sconce on the wall and go ahead and choose edit family here. Now as you can see the geometry in this family is actually pretty simple. There's just a single revolved element right here that if I click on that that represents the fixture itself. Now let me hold the shift key down and orbit a little bit, kind of spin down on this thing and what you'll see is that superimposed over that revolve is this yellow half sphere. Now this yellow half sphere is the actual light source and so if I select it, notice where it's insertion point is.
It's kind of well within this shroud here. Now normally if you did that you'd be blocking most of the light but the reason that this works just fine in this case is that when we select this revolve and we look over here at the properties you can see it's actually assigned to a glass material. And so that glass material is mostly transparent and so it allows most of the light to come through. So just make sure that if you conceal your light source that you actually have some sort of a transparent material to allow the light to shine through.
So let me go ahead and close this one. I don't need to save it. And let's look at the next light fixture. So we're going to grab this desk lamp here that's sitting on that box right there. I'll edit family. Let's zoom in. Did not need to select that. And you'll notice that most of the geometry here is related to the fixture itself. So we have several revolves and extrusions and other elements to create this fixture. Now if I select the housing here and kind of orbit Now I'm selecting something first because it controls the orbiting.
So notice that my orbiting is taking place around the selected element. Just makes it easier for me to kind of look up inside that little cone there. You can see that this is hollow inside here, so this is now the light source and it's emission point is right here and that emission point is within that hollow space. And you can imagine that's about where the light bulb would be, so that's a pretty good spot for it. Well let's get a better look at that. Let's go to elevations here and I'll do a front elevation and then zoom in and now you can see where that point is sitting.
Now if you wanted to you could actually adjust this and say well maybe the light bulb would really be about there. It's not terribly important as long as it's in that general location. Now here's the important thing about this. This is a revolve so the entire thing is hollow, even back up into here. So you could actually get away with moving this light source into really any place within this housing. If you move the light source into a location where there's a piece of solid geometry you'll get a warning like this and it says no light will be emitted during rendering so the main point that I want you to take away from this discussion is if you build your own light fixture families just make sure that wherever you put the light source you're not inadvertently blocking it with solid geometry.
Now if we intended to do that and we made this thing transparent it would still work, like we saw with the sconce. So you can ignore this warning certainly. But just keep that in mind that if you put it inside some geometry you might end up with lights that don't cast any light. And let's look at one last point here, the shape of this cone is certainly very different than the shape of that half sphere that we saw in the other light. Well with that light source selected you can click this button here which is the light source definition and there are a few different options available to control the way that the light gets cast into the space.
So this particular light is a point light which makes sense for a light bulb in a fixture like this and then it has a cone distribution or a spot light distribution. The other one had a hemispherical distribution. So it was shining in all directions. So a little bit less focused. So you can actually control -- it can be omni going all the way around, a full sphere, half a sphere, or a spotlight and then it can be emitted from a line, a surface or a circle. Now the next one we're going to look at is this special one here called a photometric web.
So to do that I'm going to close this family. I'm not going to save it. So let's select one of these recess lights and we'll edit that family. And this one you can see has this light source here that has more of a rectilinear shape so if we look at the light source definition it's just using the rectangle emit from and it's still doing a hemispherical distribution so it's casting light in all directions but only down instead of up. Now let's come over here to the views and open up the front elevation view and we can see that from another vantage point and I'm going to select that light source and I'm going to change it to a photometric web.
Now when I do that and I click okay it will remain rectilinear in terms of its emit from but notice that it will change it to this more of a ball shape and it's also tilted at a slight angle. So to control the angle that it's tilted at and to actually control the photometric web we need to go to family types. Now I'm going to go to family types and display that dialogue and scroll down and right here you can see photometric web file. Now it currently says generic and that's why it's just this simple ball and then here's the tilt angle and it's currently at 60 degrees.
Now what is a photometric web? Well a photometric web is simply a text file that has a description in it that describes the shape that the light will emit from and every lighting manufacturer has these photometric web files. They end in the extension .ies and you can go to your favorite lighting manufacturer and search through their light fixtures and they'll usually have a download where you can download these text files. Now what I'm going to do is click right here and click the browse button and I'm just going to choose one that ships with Revit.
These are more generic .ies files but you can see that there are several in here. So let's say that this is a 2 x 4 which it is, that's the shape of the light, and maybe it's a four lamp light. So I'll choose that and click open here and then I'm going to change the tilt angle to 90 degrees and when I click okay on both of those you're now going to see the shape of that ball change to become more descriptive. Now to really see that I'll go back to the 3D view and will kind of spin it around.
You can see it's got this almost like gumdrop shape to it. Well every .ies file will have these very unique 3D shapes and what it does is it just more accurately casts the light to fill the space in a more realistic way. So I highly recommend that if you're thinking of specific fixtures within your model that you go out to the websites for the manufacturers of those fixtures and see if they have .ies files that you can download. You could also download their Revit families if they have them and the fixture itself will become more accurate, but as long as you've got the .ies file and you've got it loaded in it'll actually make the light distribution much more accurate and the scene will be more realistic.
- Creating 3D views and 3D cutaway views
- Adding details to the model
- Creating and editing materials
- Working with the sun system
- Working with lighting groups
- Configuring render settings
- Preparing a cloud render
- Creating a walkthrough
- Rendering a plan