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Although we have already looked at creating artificial light types in Twilight using the Point and Spot lights, there is another option available to us that comes with a lot of flexibility and believability. In this video, we're going to use Twilight's ability to apply a light-emitting material to any geometry in our scene, and use it as a light source. In fact, what we are going to do is instead of lighting our sample spheres with an artificial light type, we're going to turn two of them into actual light sources.
We do need to say though, that this may not be something you will want to do in every production scene, particularly one that is already quite heavy in terms of scene geometry. You see, at render time Twilight converts scene geometry into triangles in order to render them. A simple SketchUp rectangle may appear to be just a single face, but at render time Twilight will actually see two triangles. Each triangle that has a light-emitting material applied to it is counted as a light source in the scene. So, if we have a sphere that appears to be made up of 40 four-sided faces or quads, it will actually become 80 triangles, and so 80 lights, at render time.
On anything other than the progressive rendering modes, this could be very bad, in terms of memory usage, and may even cause our scenes not to render. So, be aware, we need to use light-emitting materials wisely. For the purpose of our task here though, what we have will work just fine. We will be using a number of pre- prepared renders just to show you the effect that using the light-emitting material can produce. Before we examine those renders though, let's walk you through the steps of turning our spheres into actual light sources.
As we will need to apply an Emitter material template to them, the first thing we need to do is create a couple of new SketchUp materials. So, let's come up to our paint bucket icon, open up the SketchUp Materials browser. I want to make certain that I'm looking at the in Model Materials, and now I will come and create a couple of new ones. We will call our first one White Light, and we will of course make certain that it is white. And we will create second one, and we'll call it Orange Light. And of course, we want to make it orange, so I am just going to punch some very specific RGB values in here; so 175, 75, and 40. Then we can click OK.
Now, at this moment in time our sphere objects are collected together in a group, so I am just going to use the spacebar to return to my normal Select tool. I am going to select the group and then right-click and use the Explode function. Now, I can just select individual face, or I can indeed just come and select my material and apply it to individual objects. So, let's apply our orange material to that one, and we'll apply our white material to that one. I do need to do a little bit of scene setup so that we are in harmony with our test render, so I am just going to dismiss our Material Browser.
I am going to make use of our secondary scene camera, just to push in on our SketchUp Materials. I am going to come into our Render dialog. I am going to first of all make certain that we are working with the 09-Render preset. Then I want to come into the Camera Tab, and I am just going to make a quick tweak to my Exposure and Gamma settings. So, 1.25 for my Exposure level, and just a straight value of 1 in the Gamma Adjustment option. With that done, I can just dismiss the Twilight Render dialog. Now, of course we need to apply our Emitter template, so we are going to need the Twilight Material Editor.
So, let's come up to the toolbar and click on the icon for that. We can just move this off to one side because what we are going to want to do is, using the From Scene dropdown, I am going to first of all select my orange light material. We're going to come to the Templates, come down to Light Emitter, and we're going to choose the 100 Watt option. And of course, we need to repeat that for our white light material, so Templates > Light Emitter > 100 Watt. As we have been applying these Emitter templates, you have probably noticed this set of controls appear.
We have an Emitter Behavior dropdown, and we have Power or Intensity value that we can work with. Again, to bring things in line with the test renders already taken, I'm going to set my Power Output to 750 watts. The default Emitter behavior of Normal essentially means that our object will be a visible light source in the scene. It will show up inside of our renders. Let's jump into Adobe Photoshop and have a look at a render taken using this particular setting. As you can see, our light-emitting materials are working very nicely indeed.
We have a nice level of illumination, we have some very nice, very realistic soft edge shadows, and we get realistic light falloff from the material as well. All in all, a very convincing, very nice-looking artificial light source. The second option in the Emitter Behavior dropdown is entitled Fake. It is designed to make an object look lit but won't really increase the render times at all because it doesn't actually add any light into the scene. That is, if we don't use one of the progressive rendering methods.
If we do use a progressive rendering method, then our emitter will behave as if we left it set on Normal. For a fake emitter, we need to use one of the easy 01 to 07 options. If we take a look at the render using the Easy > 04 preset, you can see, essentially what we get is just a self-illuminated material. As we say, this really isn't a light source at all, but it can be very useful in certain situations when we want to give the appearance of an object being a light source, but we don't really want to add any extra illumination into the scene.
The third emitter option available is entitled Invisible, and, as its name suggests, it makes our light source invisible in the render, which will of course get our illumination and shadows in the scene. And if we just make a quick comparison between our initial render and the invisible version, you can see essentially, all that happens is our objects disappear. Maybe a little bit of the reflectivity in them disappears. You can just see that turn off as we switch between these two renders. But again, a very nice feature if we have a need, under specialized circumstances, to actually make our light source invisible.
If I just switch back the little black splotch that you see here, I suspect it has nothing to do with the Light Emitter Material, but really is just a side effect of interpenetrating geometry. The final Emitter option available, if we just jump back into SketchUp, gives us the ability to attach an IES profile to our light-emitting material. We probably would want to be careful here. We need to make certain that the IES profile we apply is appropriate to the shape of the geometry that we are applying our light-emitting material to.
All in all then, the Light Emitter material offers an easy-to-use and extremely versatile option for creating artificial light types in our Twilight renders. Do bear in mind that for anything other than Fake, which of course is not really a light source at all, we would probably be best served using one of the progressive rendering modes.
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