[Steep] Tech or method used to deform the snow ?

t_beaugelin · Sep 2017

Hi guys !

I was wondering if any of you knew what is the tech or the method used to deform the snow in the Ski game Steep by Ubi ; or if any of you had any input about how to do it ?

I've already looked for the Batman Arkham Origins Method [G DC Vault Presentation], and searched for an adapted way to do it in Unreal Engine 4. I found this guy post on ArtStation : Dynmanic Snow deformation in UE4, but this method is limited to plane surface.

So I was wondering if any of you guys had any idea on how to create deformable snow in UE4, like in Steep.

EDIT#1: Or if any one had any idea on how to adapt Sean Puller's method in order to get it working on any surface (not only plane)

Thanks all, and sorry for the english (I'm French)

Jakob Gavelli · Sep 2017

Unreal 4 pretty recently added a feature that lets you get the UV coordinates of a line-trace. Which means you can trace to a rendertarget.
Have a look at this video for the basics :

https://www.youtube.com/watch?v=1Z-V1Buk6z8
I don't know if this is exactly what you're looking for as I never saw or played Steep, but should be ONE solution to the problem?
Using this technique I made a blueprint that can replace any staticmesh or landscape to support this kind of deformation:

Froyok · Sep 2017

You may find some insights in how the snow deformation was made in AC3, since they had non-planar surfaces as well. https://www.gdcvault.com/play/1017710/Rendering-Assassin-s-Creed

marks · Sep 2017

There's some talks about one of the Tomb Raider games recently that did a similar thing, in a similar way, but I don't have a link

t_beaugelin · Sep 2017

@Jakob Gavelli Okay ! You method seems pretty great ! Might lok at the video you have given to me

Thanks ! One question, does this method support non plannar surface ? I guess it is, since you can attach the render target to the feet.

@Froyok I'll defintly look at this !

@marks If you find a link, I'm taking it !

Thanks all for your quick answers !

Jakob Gavelli · Sep 2017

yeah, doesnt matter. It's a trace down from the feet, what it hits gets deformed. Doesn't matter what angle or whatever it hits.
The drawback is that EACH object you want deformable needs a separate black/white texture with probably 128x128 up to 1024x1024 resolution depending on the size of the object.
So for a massive landscape I don't think it's viable unless you come up with a clever solution. Such as using chunks and unloading the textures or something. So this technique is probably most suitable for smaller areas of deep snow, and not an entire gameworld.

t_beaugelin · Sep 2017

@Jakob Gavelli Well for the moment, only the player needs to affect the deformation, so it shouldn't be so heavy to do.
Any input on how you made it, please pretty please ?
Thanks !

Jakob Gavelli · Sep 2017

Look through the 1 hour video I linked, he goes through his material and blueprint setup in a pretty detailed fashion, and from that you should be able to recreate the inverse of what he does in the video. Attach the Linetrace to a footdown event or whatever and there you go ^^
It does require a basic knowledge of materials and blueprint to get it up and running! So get to it!

If you need help with it show what you've got when you've tried some different approaches and we can see what's up!

t_beaugelin · Sep 2017

@Jakob Gavelli Okay ! I'll look at his then ^^

marks · Sep 2017

t_beaugelin said:

@marks If you find a link, I'm taking it !

You've heard of google, right ?

Obscura · Sep 2017

First and last try... U use a render target and you draw a distance to a point so you get a soft circle. You use an additive kind of render target and you just update that with the fed player position. You need to use "draw material to render target" node and before that you feed the player position into the sphere renderer so it aligns to the player and then you just draw it. But yeah....^

RN · Sep 2017

Please correct if wrong.
The deformation itself is done in the vertex shader of the snow mesh. You sample the render target texture in there and then move the snow vertices down from their original position based on the colour that you sampled (the same colour that you're using to define steps on the render target).

You can then do some things like fading the render target back to its "neutral" colour with time, so the oldest snow steps raise back again.

Obscura · Sep 2017

I think that is only possible with 2 render targets. One rendered as additive and a simple overwrite one. And you would render the simple one when the player doesn't move and you would subtract it from the final material. I'm not sure though, I haven't tried this, but this would make sense.

t_beaugelin · Sep 2017

Hello guys !

If I've made some progress, and I want to show what i got and ask for help, should I start a thread in the UE forum ?
Because it's not really related to do it here, so I was wondering...
Anyway, I'm posting it here :
For the moment, I'm trying to reproduce the method used for the first part of the video @Jakob Gavelli linked, but in the same time trying to adapt it in order to make it work with the feet of my character... I think I'm close, but it appears that either I'm badly doing my LineTrace, or it is bugged. The black plane is the plane where the magic is supposed to happen. (See screenshot).

Image: https://us.v-cdn.net/5021068/uploads/editor/dd/oeli6hsl7bau.png

Image: https://us.v-cdn.net/5021068/uploads/editor/t8/zggdd6y07rnu.png

The trace is working great on a "normal" plane, but when I walk on the Blueprint plane (like I said, for the moment I'm following the vid), the trace suddenly does not work correctly anymore.
Any advices ?

Thanks all for your input !

PS: @marks Yeah I know google, just thought you could have saved it...

Obscura · Sep 2017

If this is for footsteps, I think its much simpler to just attach a collision volume to the foot, and binding an event when it intersected with the ground. No need for ray trace.

t_beaugelin · Sep 2017

@Obscura No no, its not for the footprints. My footprints system is working perfectly. When I'm walking on the black plane, it is supposed to leave a white dot after each step, this dot being a little higher than the plane.

EDIT#01: In other words, when walking on the black plane, it is supposed to displace geometry, on the location of the LineTrace. But the linetrace is not working properly, so I don't know if the deformation system works or not.

Obscura · Sep 2017

If you show the line trace graph, maybe we can find it out why it isn't working correctly.

t_beaugelin · Sep 2017

Okay, so here it is.
The "LeftFootArrow" node coresspond to the red arrow under the left feet in Character Viewport. (The red arrow are used for my footprint system)

[Steep] Tech or method used to deform the snow ?

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