The Reflectance Channel, Part 05: Basic Material Setup from Scratch

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Instructor Patrick Goski

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Setting up a material that has both specular and reflective properties from scratch.

In this video you’ll create a material that has both a specular layer and reflective layer from scratch. You will learn how to manually add both layers, adjust the Specular and Reflection strengths, change the Attenuation and Roughness, and adjust the layer blending, hierarchy and masking.



- In this video, we're going to take a look at creating a reflective material with a specular using the new models for both of these layers. So we're going to start by creating another new material, and this will be "Owl Body 2". We're going to apply this material to the owl body, and again we can render just to see the starting point with this material. Now, we're going to go back to the Reflectance layer and go to the Default Specular. Again, you'll see that it's set to Add Mode here. The type is the Specular Blend Legacy, and it is using the additive attenuation. If we wanted to use one of the new reflection models for our specular, we would want to select one of these from the list. In this case, we're going to work with GGX. When you do this, you'll see that it already comes in with a specular that is showing properly, and this is because it's taking all of the attributes from that default model and passing them over to this GGX model. If we started with absolutely no layer in here and added a new GGX layer, you'll see that it comes in with a reflection strength of 100% and a specular strength of 20%. If we are building this from scratch, the first thing that we need to do to use this GGX model is to start adding in some sort of roughness to get the specular to actually show up. If we hit Render, you'll see that all we're going to get is a 100% reflection. Even if we increase the specular strength on this, it's not going to change the actual look of this render. It's still just going to be only the reflection that's visible. So, to see some sort of specular contribution, you need to increase the roughness. As you do this, you'll see the graph here is going to display the fall-off for this reflection model. The actual reflection fall-off is on the left and the specular fall-off is on the right. If we render now, what we're going to see is a contribution of both the reflection and the specular. So with this render finished, you can see the effects of both the specular and reflection together. The issue here is that we don't have independent control over the roughness for the specular or the reflection itself. So we want to create two layers of GGX. One of these will be purely reflective, and the other will be purely specular. So we're going to start by setting up the reflective layer. This means, we'll set the specular strength down to 0%, and now we have control over just the roughness of this reflection layer. So we'll set this to something fairly low, like 10%, just so that we get a little bit of roughness in here that will soften this up, and we can render again. Next, we want to decrease the actual amount of the reflection. Again, we're not going to change the reflection strength, as doing so is just going to overwrite the color channel completely. What we want to do is only adjust the layer mask amount for this, allowing a little bit of the color channel to come through. Next, we will add a layer Fresnel onto this. So we'll just choose the dielectric again, and this is going to add a little bit of fall-off based on the camera angle and again we can click on Render. At this point, we're going to add the second layer, and this is going to be used for our actual specular. So we'll click on the Add button, and then choose GGX again. Since the first layer is going to be a reflection, this new layer is going to have a reflection strength of zero and a specular strength of 100%. You'll see that with these settings all we're getting is a completely black material, and if we render we're going to see that reflected in the render. So the first step is going to be adding some roughness in here to actually control the fall-off of this specular. Now that we've done that, we actually get some sort of effect from the specular highlight, and we can render to see results. Because we're not actually using an attenuation that blends this with the color channel, we need to start working with that. So the first thing we need to do is change the attenuation. This is going to change from Average to Additive, and then we can click on Render to see the results. We can now see the results from the specular and the color channel below. If we want to see this blended on top with our actual reflection, we're going to set the blend mode for this layer to Add. This means that it's going to be blended with the reflection layer. So we can click on Render again, and we'll now see that we have a blend of the reflection and the specular itself. Now, if we want to control the strength of the specular, we're going to adjust the layer mask amount for the specular layer. As we reduce this, we can get something that is closer to what we want. So to recap, we started with one reflective layer, in this case GGX, with the attenuation set to Average. The reflection strength is set to 100% and the specular strength was reduced to zero. This means that we're only getting reflective contribution from this layer. We added a Fresnel mask to control the fall-off based on the camera angle, and then we used the layer mask amount to control the amount of the actual reflective layer. We then added a second layer, also with the GGX shading type. This time the attenuation was set to Additive, allowing this specular layer to be blended with the color channel. The roughness was used to control the actual fall-off for this specular effect, and then the Add Mode was used to control how that's blended with the reflection layer. Again, to control the overall strength of the specular, we used the layer mask amount rather than the specular strength. This is something just to keep the workflow consistent between working with your specular layer and your reflective layer. But because the specular layer is using an additive attenuation, you could also use the specular strength to adjust the strength of the specular contribution.
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