Foliage collision + foliage bend on collision- In engine feature?

[anonymous_user_550b73f9]

@comet;11897

My brain just always pictured it as “invisible sphere of influence attached to player touches grass = grass moves.”
And that could somehow be a “system” not relying on global parameters. Thus, my focus on collision.The sphere and grass just need to know they are touching each other and grass reacts according to its material programming.

You could approach it from this direction, ie enable CPU-calculated collision on the foliage, and when a cluster of foliage instances get a collision notification, find which instance it is and move it etc. This all gets a bit messy because the individual instances of foliage are grouped together in a single component for rendering efficiency. You’d probably want to hide the instances being hit by the player and replace them with individual components that you then simulate etc. A GPU-only solution is more efficient and scalable, but doing things on the GPU sometimes requires you think backwards from the point of view of each independent piece of foliage as it’s being rendered :-).

@comet;11897

You used the term “material.” Is it a material that bends the grass, and not shader? I was using shader for my questioning. I thought that’s how I could get foliage to bend because coming from Unity, it is a shader that bends foliage. Like the wind shader.

In Unreal-speak, the Material is higher-level the network you graph you build, where as Shaders are the lower level HLSL or GLSL code generated from the material graph. Note that one material might generate a number of shaders used for different purposes but that’s mostly hidden from the user. We do use the terms independently to some degree. In this case using the World Position Offset input causes the material to generate code inside the vertex shader to move the foliage.

@comet;11897

It would be wonderful to have the the foliage bend example material mentioned in the document.

I spoke to the artist who made the content in the doc screenshot. That content is from Fortnite, one of our internal games under development, but he’s going to port that material to plain UE4 and build a small example which we will make available to you guys.