Megascans beta - some very quick tests

[John_Do]

Hello,

Megascans was finally released in public beta yesterday, there is some free stuff to test the service. It lets you choose the maps to donwload according to your workflow, offline or realtime rendering, specular or metalness, roughness or glossiness, very very convenient ! And you can download all map at the same time or only particular one, very useful.

But...

PBR CALIBRATED
Surfaces come with real-world Albedo, Normal, Displacement, Translucency, Cavity/Specular, Roughness/Gloss, Metalness and AO, all calibrated to the standard Disney Principled BRDF.

...the problem is here.







Raw renders from V-Ray, no post.

It seems that the lack of reflectivity dimming at low glossiness / high roughness is the main responsible, since it's the major difference between "PBR" shader and one from an offline renderer like V-Ray, even if it is based on Disney paper. ( see here for a little comparison )
But even Modo, which have a "Physically Based" shading model, fails. You can tweak the fresnel to correct the bad interpretation, it's better than V-Ray Mat but not quite there yet, and it's not the out-of-the-box solution that Quixel promises.

But at least we have the Unreal Material and it really shines with these textures, just drag-n-drop the maps, and you're ready to render !

[John_Do]

Direct comparisons

[vladimir.nedev]

Where it says "V-Ray", is that with the V-Ray material or Unreal material ?
Where is says "Unreal", is that directly from the Unreal engine viewport ?

Did you disable the Unreal bloom/glare ?

Greetings,
Vladimir Nedev

[John_Do]

Hello Vladimir,

When it says V-Ray, it's a V-ray Material, and with Unreal, the Unreal Material. All images are rendered inside Modo with V-Ray, I didn't try yet inside Unreal Engine, but the result with Unreal Mat is pretty close to the render on Megascans website : https://megascans.se/library/free ( see the soil mud material in the top right corner, not as rough as the V-Ray mat result ).

I did some crap with materials settings in my first test. Here is a correct and more understable version.









The glossiness is very different, so different that I'm wondering if there may be a problem with textures colorspace ?

You can download the scene here :

quixel_test_scene

[John_Do]

Okay, I absolutely don't know why but I have to set my gloss map to a gamma of 2.2 and double it to achieve the same gloss level as UE material Oo ( so gamma 4.4 on the gloss map )

[vladimir.nedev]

Okay, I absolutely don't know why but I have to set my gloss map to a gamma of 2.2 and double it to achieve the same gloss level as UE material Oo ( so gamma 4.4 on the gloss map )

[ATTACH=CONFIG]32336[/ATTACH]

Are you using GGX with the V-Ray material ?
I guess, but just to make sure.

Greetings,
Vladimir Nedev

[John_Do]

Yes of course. I'm dumb but not this much

[vladimir.nedev]

The json file that comes with the textures says that they are in the sRGB color-space.
I guess this will be the case for all free samples, although I checked only one.

Their help says "Roughness represents how rough the surface is, dictating the spread and intensity of specular reflections, and is the inverse of Gloss/Smoothness."

And that seems to be true, if you invert the roughness texture (in say Paint.net), you get (almost) exactly the glossiness texture.
I think Paint.net (and probably Photoshop) just inverts the pixels as they are in the sRGB color-space.
For correct conversion, you need to bring the pixels in linear space, invert them and then back to sRGB before saving the image.
That's how V-Ray/MODO will do it, if you enable "invert" on the texture layer.

So, maybe they messed up their conversion process from glossiness texture to roughness texture, by doing it in the sRGB space instead of linear ?

If we assume the glossiness one is the correct one, you can just use it in place of roughness by checking "invert" on the texture layer.

Greetings,
Vladimir Nedev

[John_Do]

So, maybe they messed up their conversion process from glossiness texture to roughness texture, by doing it in the sRGB space instead of linear ?

If we assume the glossiness one is the correct one, you can just use it in place of roughness by checking "invert" on the texture layer.

You nailed it inverted roughness gives same result as the Unreal Material, see below





Finally it's a convenient "feature", since we don't have to store the 2 kind of map.

I didn't have the idea to open the json file, there are interesting things in it !

EDIT :

Here is the final version.



- Unreal : inverted glossiness, linear
- V-Ray : glossiness,linear

I have changed the colorspace for Linear since the json file indicate that it's the right colorspace for microsurface maps.

The results can't be much closer, except for the reflection ring a grazing angle :/ I tried to use a custom falloff to fake the dimming of the reflection, but it's quite hard to replicate since I have to mix it with gloss map setted on Reflection Color. ( to fake the impact of glossiness on reflection ).