The Reflectance Channel, Part 11: Using the Reflection and Specular Strength sliders

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Instructor Patrick Goski

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A look at the Reflection and Specular strength sliders.

This video explores the Reflection and Specular Strength sliders and how they affect the results of the reflection layer, as well as when you should use them and which attenuation methods can be used with each.



- In this video, we're going to take a look at the reflection strength and specular strength inside the reflectance channel. First thing that we'll do is create a new material and rename this, "Owl Body." Then we will apply this to the owl body in the object manager. We can click on the material again to bring the properties back up in the attribute manager. By default, the material is going to come in with a default specular inside the reflectance channel. For the purposes of this video, we're just going to remove this and start with the Beckmann shading model. When we add the Beckmann shading model, there's a few things to note when dealing with the reflection strength and the specular strength. First off, the models will come in set up for a reflection, but they will also have a bit of contribution added from the specular strength. The other thing to note is the attenuation. In this case, it's going to be set to average. We're going to start by taking a look at just the reflection strength, so we can go ahead and set the specular strength to 0%. We're then going click render to see what we're dealing with. With that render complete, you can see that the reflection strength of 100% is giving a mirror quality reflection of the environment around. The reflection strength is going to control the contribution of the reflection in this particular layer. We can control this from 100%, which is the full contribution, to 0%, which is no contribution, and you'll see in the preview, we get a black contribution to the overall reflectance. Also, if we take a look at the material preview itself, we'll see that the material is now black, and if we render to the picture viewer, we get the exact same result. This is because the reflection strength is, again, going to show us either black or a full reflection, and anywhere in between. Because the attenuation is set to average, it's going to overwrite the color channel completely rather than blend with it. So in this case, we could possibly set the attenuation to additive, which would add black over top of the color channel. If we click on render, we can see here that we can see the color channel again, but there's no reflection. If we go to the reflection strength and increase this and render again, what we'll get is something that is not exactly physically accurate, because in this case, everything that's coming from the reflection, which we can see here, is being added on top of the color channel, which produces over bright results. So in this case, when dealing with the reflection strength or a reflective layer, the attenuation must be set to average or maximum. When it's set to average, it will overwrite the color channel completely, but if we want to see some of that color channel coming through, then we're going to use the layer mask amount for this reflectance layer. Now if we render again, we can see the proper color channel coming through, but also the reflectance blended in correctly. Now, if we were to do this with the specular strength, we'll see something similar. We'll see the layer mask amount back to 100% and drop the reflection strength to 0. In this case, we're going to have no contribution from the specular or the reflection on the object. If we increase the specular strength, we'll see that there's still nothing happening in the preview, and even if we render, we're not going to see any result. Since we're using one of the four top shading models, we first need to add some roughness before we'll see any contribution from the specular. So as we increase the roughness, we can now see the specular spread out on the actual preview. If we take a look at the material preview, we'll see that we're still not seeing the color channel through there. And if we render, we're going to get a similar result. Again, this comes down to the average attenuation method. If we set the specular strength to zero and render, we'll see that we get no contribution to the specular. Setting it to 100%, we get the full contribution from the specular. But to actually get this to blend with the color channel, we need to set the attenuation to additive. This way, it's going to added on top of the color channel, and when we render, it will render correctly. Because of the way that the specular works, and it because it needs to be set up with additive attenuation, we can safely adjust the specular strength to control the height of the specular. But to keep things in line with how we'll be working with reflections, it's a good idea to keep the specular strength at 100% and again, just use the layer mask amount to control the overall height of that specular highlight. The next thing that you have with the reflection strength and the specular strength is a shader slot to modulate the strength of these across the surface. So you can see that both of these have an arrow that you can twirl down. So first, we'll set the specular strength to 0 and the reflection strength to 100%, and increase the layer mask amount to 100% as well. We'll switch the attenuation method back to average and set the roughness to zero. Now, if we twirl down the reflection strength, you'll see that you have the option to add in the texture. This could be a bitmap or a shader. If we do that, you'll see that it modulates the strength of the reflection across the surface. And if we increase the contrast, this will become more apparent inside of the preview. If you render this, you're going to see that you will get areas that are 100% reflective and 100% black. This is because of the attenuation method, where it's overwriting the color channel. So again, you probably don't want to use anything in here that will reduce the reflection strength, unless you're using an additive method. But when you're working with reflections, this isn't going to produce realistic results. We can also clear this to get back to the 100% reflection. The other thing that we have is a check box, and if we click on this, it's going to enable the colored model. And what this does is source the color from the color channel and use that inside of this texture link field here. So, if we were to change the color of the color channel to something like purple, we'll also see that the reflection is going to take on some of that quality. And if we click on render, we'll see that we get a fairly purple reflection of the environment around the object. So just to recap, we added in a Beckmann shading model and set the reflection strength to 100%. We can have the roughness at 0%, but if the attenuation is set to additive, we're going to get incorrect results when we render. In this case, we're getting a reflection that is added on top of the color, producing over bright results. So when working with the reflection, we want to keep the attenuation set to average or maximum, and then only adjust the layer mask amount so that we can see through this reflective layer to the actual color channel. When we're working with the specular strength, we need to have the specular strength at 100%, and some sort of roughness so that we start to see the specular. Because of the way that a specular works, the attenuation method must be set to additive. This way, it's added on top of the color channel. We can then use the specular strength to adjust the height of the specular, or to keep things similar to working with a reflection, we can adjust the layer mask amount to control the height.
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