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By Max
#392414
Hey guys, i've been tryin to achieve a good looking snow material since a while. Not the easiest thing in the world!
I've gathered as many references and other render engine user renders to see how they approached it.

So far looks like most people go without a subsurface approach, because it is very expensive in render times. I've tried both ways, and personally while the non-sss method is fine for far landscape, exteriors and ideally objects that are far from camera, when you have something you want to give a bit of detail, you have to go with sss.

Anyway i wanted to gather some tips if you have any, here is what i have done so far, its still in progress

Image

Most problem i am facing is to give to the shader enough glittering effect, that microfacet reflection that happens when its being hit by the sunlight

Anyone did manage to achieve a snow shader in maxwell? I've seen some impressive vray shaders but im no vray user and also i like challenges!

This shader is made of 4 layers, SSS base, diffuse, a reflective layer set on glossy, and the sparkling glittering level, which at the moment is giving me some trouble. The sss gives a nice touch to it, if you check the rabbit ears, still have to improve

comments are welcome

Max
User avatar
By eric nixon
#392620
This is my current snow material I'm using for large areas, there is no diffuse component, its just very rough refraction with a little sss to mimic the crystals inside - (technically snow doesn't really have any sss), and then 1 additive spec layer on top. Its still pretty slow but its not noisy-slow, the normal noise map is just to stop it from rendering too smooth at high sl.

For a smaller scale snow object (like your bunny), you could introduce some rough displacement (which would be impractical for a large ground) and then use a lower roughness like 60.

In my case the ground is an animated deforming object as the car drives through it, and its an open mesh, so I needed to add a pure black cube object underneath to terminate the rays passing through it. This is actually a good idea anyway to make sure you don't get any light coming through from the hdri underneath.

There is no easy way to achieve refractive sparkles I would resort to instancing glassy crystals across the surface, if your pc can handle it. I didn't bother with that because I want to animate this, and it will be motion blurred.

Image

Finally you could also generate a material mask and brighten in post.

Here is a mw1 render of displaced snow roughness 60 sss assymetry -0.2;

Image

Final thought about refractive sparkles, I haven't tried this yet, but maybe adding some weightmapped sss with very possitive assymetry could mimic the effect, this fabric uses 0.8 assym;

Image
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By eric nixon
#392655
Thanks, I simmed the snow spray with realflow inside c4d (which runs really well btw), I need to resim to get the timing right, and also the direction of the roosts seems wrong, gotta fix that. The snow on the tyres is also dynamic (simmed) with x-particles.
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By tom
#393060
Very realistic snow, indeed! Liked that small dune...
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By Mihai
#393420
But that's just a spec layer, like you would have when creating any plastic for example. Just set it to some normal Nd like 1.5, turn on force fresnel and roughness low, like 2-5.
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By eric nixon
#393472
Actually my previous example was a bit flawed, I did some more tests, I'm still not happy with it really, I feel like it needs to be overexposed to look convincing for closeups, but maybe the lighting is wrong, because it really depends on the lighting to look right..

Like Mihai said the spec layer is just a simple low rough nd 1.33, but it does use the normal map I showed to get a sparkly effect. I ended up weighting the spec layer at just 10-15%

For the main layer I have now ditched the normal map completely, set the sss assymetry to -.15 and increased the coeff but made it light grey, not white.
In the end I felt the material using lambert was too dull but using roughness-60 was too slow to render, so I duplicated the bsdf using roughness-0, and gave the new bsdf 25% influence.

For some reason additive mixing doesn't work with particles (you get noise), so I cant make the snow spray as bright as I'd like. Hope that gets fixed, setting up the volumetrics for this scene was also tricky and totally against what the docs say. (That should be fixed also)

MW4 render, (mw3 version looked slightly softer, but I'm not sure,... half blind from staring at snow tests...)

Image

Sorry the van isn't textured yet, not sure which van to use.
User avatar
By Rafal SLEK
#393517
Wow, looks so real :-)
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