Rope Physics Grass blowing

General Discussion
#1

Looking for a starting point and advice on how to do some physics for ropes and grass blowing based on this video.

pick up mark 1:25-1:45 drop mark 3:00-3:32

Can this be done in UE or is this something that would be better done in blender and then brought into UE.

Thanks

#2

Hello alexmont,

so for the rope physics it is hard to tell, as it really depends on many factors. Generally answering this question is hard if there are no details.

For the blowing grass:
I would set up vertex animations in the foliage material that gets effected in a specified radius around the effector (helicopter). Having the WorldPos of the effector not only enables you to use the distance for generating a nice falloff for the turbulence noise in the material, but also you can use that info to tilt the foliage slightly away from the effector. This even more sells the impact on the environment of the helicopter.
Depending on the game, you could even use a rendertexture + particle system to fade out the turbulence. Similar to how it is achieved in Ghost of Tsushima:

(from this blog entry: How stunning visual effects bring Ghost of Tsushima to life – PlayStation.Blog)

Did you already tried out some approaches before? I know these are general answers, but with more details you could get more detailed help.

#3

Thanks for the response.

I did not try any approaches just yet. I was toying with the idea of doing it in Houdini and using the Houdini Engine to get it into UE.

I am really intrigued by the vertex animation in the foliage material method that you referenced. I have not done anything like that before. I am going to read the article you referenced then look for some more info on this.

Appreciate your time
Thanks
Alex

#4

So I started working on the rope part of my question yesterday. I am looking for a little help to clean this up. Right now the cables are too stretchy and I am not sure if I have the correct setup for the physic constraints.

I have enclosed some screen shots of some settings and a small video .

Thanks!

screen video

2022-03-08 16_37_49-Gun
2022-03-08 16_37_49-Gun1899×943 472 KB
gun2
gun21895×983 491 KB
gun1
gun11895×940 499 KB

#5

Hello,

so truth be told: the rope/cable system from Unreal is not great in my opinion. It really feels uncontrollable.

In projects I was working in, we either

  • fake simple movements in shader (like, if heavy wind is blowing against it)
  • bake an animation (for cutscenes or things that don’t need to behave dynamically)
  • use a 3rd party real time rope sim (if it really needs to be dynamic)

Maybe in your case, the second method could suffice. You can even blend two animations, to give it a bit off visual variety. And it will not be as expensive as the third option.

#6

I am coming to that conclussion, that its very unpredictable and just doesnt work like I was hoping.
I am trying one last thing but if that deosnt work I am just going to have to do it in Blender and import the baked animation in.

I ll let you know how it goes.

Thanks