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Our exposure looks pretty good, but we're getting some strange highlighting on the front face of the watch glass. That's actually coming from the Skylight, and as I said earlier, the Skylight is optional. In fact, we could turn it off in this case. But we need to be aware of what we are doing, because the skylight is the only source of diffuse illumination and shadows in this scene. So the Skylight is providing all the diffuse light as well as shadows. And the environment map is providing all the reflections.
Well it just so happens that this watch is almost all reflections. The watch band has no diffuse component, because it's diffuse color is black. And the watch face has a diffuse amount of only 0.3. So if we completely disabled all diffuse illumination here, we would not see that big of a change. Let's take a look at that. Select the Skylight and turn it off. And do another rendering, see what it looks like with no diffuse illumination.
Now we're getting only reflections. And it actually has solved the issue with the front face of our glass and it's made the gold or brass of the watch face look more contrasty because now there's no diffuse light hitting it. However that's not really a solution in all cases. I mean it kind of works here, but I've got a test object here, this teapot, I'm going to move it into the frame so we can demonstrate the issue. So I will re-enable the Skylight and Render it with that teapot in the frame and you will see that we do have that pink tea pot showing up.
Okay, so that's what we are supposed to get but if we disable that Skylight then this will render a solid black. Go ahead and cancel that render in progress. Turn the Skylight off once again. And you'll see it's now, it's icon is in black and do a render. And we get no diffuse illumination. So the teapot renders as solid black. Because a teapot has no shiny highlights on it, it's all diffuse and we've disabled the diffuse component by turning off that Skylight.
So, yes the Skylight is optional, but you do need to know what you're doing. We do want it on actually in this case. I'm going to delete the teapot and turn that light back on again. Yeah, we want to have a little bit of diffuse component here. But we want to get rid of that pesky highlight that we're seeing on the glass, and the answer to that is to go back in to the glass material. So we'll go to the material editor, and zoom out with the wheel, and we should still have our glass material here somewhere.
Here it is, and if it's not in your scene then, of course, you can go in to the material map browser and go in to. The scene materials and drag it back in. We've got it just here. So double-click on that glass material. And what we need to adjust here is the BRDF settings. Remember that stands for bidirectional reflectance distribution function. And it has to do with the reflectivity of a surface, whether it's pointed towards the camera or at 90 degrees to the camera.
The glass template that we chose earlier in the course has bi IOR firnel reflections enabled. And that means that the reflectivity is going to be determined by this index of refraction parameter up here. If we change the IOR here, it's going to change the reflectivity, as you can see. The IOR of 1.5 is in fact accurate for glass. So we do want that to be set, so we'll get accurate refractions. But our reflections aren't quite working out.
We need to choose custom reflectivity. We'll need to set the zero degree reflection to zero. Remember that's the reflectivity of surfaces pointed towards the camera. And that will get rid of our weird highlight that we were seeing. Additionally, we've got the curve shape here, which is the falloff ratio. And so we can get some highlighting on the edges of things. We're going to set that curve shape to a value of 3. Okay. So we've got that sorted out. We'll do another test render. We've got our Skylight turned back on.
And we are getting our diffuse illumination down here. And we're not seeing that weird highlight on the front of the glass face. Okay good. So that's what we get, after having adjusted that glass material. The last thing we want to adjust here is the bump mapping on the material here. It's not quite right, it's a little bit too strong. I'm going to clone that window off so we can compare it. And go back into our material editor. And we're looking for the watch body material.
Double-click on that. I just want to reduce the bump amount a little bit. The value of 0.15 worked well in our studio lighting setup. But in this more obvious reflection on here. It's just looking a bit too bumpy. So I'm going to set that down to 0.5 and then do a final render. Alright. So we've got a really nice rendering here with image-based lighting. Once again we'll have to replace this background in post. We don't really have a choice around that. However, in the movie I'll show you an alternative method of image-based lighting with geometric sphere.
In which we can actually put whatever environment background in there if we want.
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