Another portion of tips and tricks from Alireza Khajehali. All you need to know about mixing Megascans materials with Unreal Engine 4. The best material setups for optimal results.
I had some requests for a tutorial from people regarding their Megascans materials not looking correct inside UE4, and I thought I’d do some tests here, mostly doing different setups and making comparisons in order to find out what material setup works best and is most cost efficient. I did 7 tests and I’m sharing the results below and I hope it helps. Please note that the number of each test corresponds with the numbers seen on the images. Half the surface is covered in shadows to see the changes both under light and shadow.
1. Albedo + Normal + Roughness + Specular 0.5
With this setup you see missing AO on the entire surface, as well as an unpleasant uniform reflection.
2. Albedo + Normal + Roughness + Specular 0.5 + AO
We add the AO map to the AO input. You see there are some very subtle AO introduced, but only in the shadowed part. The lit part on both sides remains without AO and fine shadows. Both sides still have uniform reflection as well.
3. Albedo + Normal + Roughness + Specular 0.5 + AO + AO Multiplied on Albedo
We multiply the AO on Albedo. This introduces fine shadows to the surfaces and the lit areas start to look nice. But since AO is only affective in the shadowed parts, it gets coupled with the AO that’s multiplied on Albedo and creates over occlusion on the shadowed parts.
4. Albedo + Normal + Roughness + Specular 0.5 + AO Multiplied on Albedo
We originally added the AO map to the AO input in order to have fine shadows on our surface, but it resulted in over occlusion when we multiplied the AO on Albedo. Simply disconnecting the AO map from the AO input gives us consistent fine shadows on both lit and shadowed areas. Now we have those fine shadows sorted out, but the unpleasant uniform reflection is still there.
5. Albedo + Normal + Roughness + Specular 0.5 Multiplied by Cavity + AO Multiplied on Albedo
We multiply the Cavity map with 0.5 and plug it into the Specular input. The dark parts in the Cavity map will reduce the 0.5 value (where we have fine shadows and shouldn’t receive as much light as we do from the rest of the surface) and this breaks up the uniform reflection. The result looks nice now however, there’s one big issue. We are using too many texture maps for one material (5 textures). Now we look into reducing that.
6. Albedo + Normal + Roughness + Specular 0.5 Multiplied by AO + AO Multiplied on Albedo
We take out Cavity and instead we multiply the AO map with 0.5 and plug it into the Specular input. The result isn’t 1:1 with a Cavity map as you see in the Specular Buffer.
7. Albedo + Normal + Roughness + AO Multiplied by itself then multiplied on 0.5 for Specular + AO Multiplied on Albedo
The result looks acceptable now, and when in Lit mode, the difference is subtle that people don’t notice it in game, yet we have reduced our texture count from 5 to 4 which is a big gain.
To further reduce the texture count we can put our Roughness into the Normal map Blue channel, and put the AO into Normal map Alpha channel. Having done this the compression type on the normal map needs to be changed from “Normal” to “Masks”. The normal map Blue channel is reconstructed inside the material editor. Our texture count is reduced from 5 to 2.