The Reflectance Channel, Part 12: The Bump Strength

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Instructor Patrick Goski

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An overview of the bump strength attribute and it’s additional controls.

In this video you will learn about the Bump Strength attribute and the effect it has on a Reflectance layer. Beyond the Bump Strength slider, you’ll learn how to modulate the bump strength with a texture, and how to use Custom Bump or Custom Normal maps for individual Reflectance layers.

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Transcript

- [Patrick Goski] In this video, we're going to cover the bump attributes inside of a reflectance layer. So the f irst thing that we'll do is create a new material and rename this to "Owl Body", and apply that to the owl body in the object manager. We can then click on the owl body material to get the attributes inside the attribute manager. If we go to the reflectance channel and then click on the default specular, we can then click Remove to get rid of that, and we'll just add a brand new reflectance layer, in this case, Beckman. We're also going to set the specular strength down to 0% because we don't really need to look at that to be able to see what's going to happen with the bump strength. The bump strength is going to allow you to control how much the bump from the material attributes is going to affect the specific reflectance layer. So, we'll want to start by enabling the bump channel, and then in the bump channel, we'll add a simple noise. We'll scale this noise down so it's a little bit more bumpy on the surface, and then go back to the reflectance channel. In the material preview, we can see that the bump is affecting the entire surface, and we can render to see the results of that. So here, we see the material reflecting the environment around, and then the bump channel is controlling just how much that is going to be bumpy. The slider then allows us to control how much of this effect is applied to the actual reflection. So if we set that to 50% and render again, we'll see that the bump strength is going to reduce. So, it seems less bumpy than with 100%. If we set the strength to zero, we can see that we get a perfectly smooth surface again. The key thing about the bump strength is it's only affecting this reflectance layer, and it will still affect the diffuse or the color beneath. So if we go ahead and hide the reflectance layer and render, you'll see that the surface that we get is still going to be the same object with the bump applied. But enabling the reflection layer again means that we will see the reflection perfectly smooth. If we then change the layer mask amount, we'll be able to see the bumpy surface underneath, but then the reflection is not affected at all by that surface. This allows us to get an effect of a clear coat over top of the bumpy surface. If we enable the bump strength, we'll see that the reflection is going to match the color again. If we twirl down the extra options for the bump strength, we'll see that we have a texture link field, and this can be used to modulate between the full effect of a bump and no effect. So if we add in a Fresnel shader, and just set this so that we have a fairly high contrast between where we would have the full effect of the bump, which would be white, and no effect of the bump, which would be black, and render, we'll see that some parts of the reflection are not affected at all by the bump, and then other parts are going to have the full effect of the bump. And if we turn the layer mask amount back up and render, you'll be able to see this a bit more clearly. So here, we can see no effect of the bump and then full effect of the bump, and this is based on the texture, which is modulating that bump strength across the surface. The next thing we have is a mode, and by default, this is going to source the bump from the bump channel. But we can also add in a custom bump map or a custom normal map. And using either of these options will allow you to override whatever is coming from the bump channel. So if we set this to custom bump map, we now have a link field for adding in a custom texture. The texture above is still going to control the modulation of that bump strength across the surface. Let's just start by clearing this and only use the custom texture for the bump in this reflection layer. So, we'll also add in a noise to this custom texture, and then set this to something different, like wavy turbulence. We can then increase the contrast a bit so that the effect will be more pronounced, and we'll also decrease the scale, just so it's smaller across the surface. Now if we render, you'll see that the bump is going to use that wavy turbulence that we set. Because this is a custom texture just for this reflection layer, if we decrease the layer mask amount and then render again, we're going to see the bump from the bump channel affecting the color. But then the custom bump map that we're using is affecting the reflection by itself. If we set the mode to custom normal map, this will give us the same controls, but this time we'll be relying on a normal map rather than a bump map. So just to recap, in this video, we covered the bump strength, which allows us to modulate the amount of effect that the bump channel will have on a specific reflection layer. We also covered the differences between the default and a custom bump mode, which allows you to either source the bump from the bump channel when using default, or using a specific custom texture or shader to control the bump for that specific reflection layer. We can also use the first texture slot to modulate the strength of the bump across the surface. And this can be used in conjunction with either the bump channel or with the custom texture.
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