Wind force reducing object bind influence

[kysterama]

Hi! Hope someone can shed some light on this issue I'm having

My scene has an alembic Phoenix ocean surface and Tyflow is handling the floating debris/props

I'm using object bind with snap to surface + 100% linear spring. 

   

As soon as I add wind though, the props go above and below the water surface and seem to overide or lose the snap to surface binding influence resulting in hovering objects.

My first though was accuracy and Time Steps so set that at 1/8 but for some reason I have to set the wind to 8x the value to compensate and the problem still occurs.

Is there a way to keep the object bind and still get the props to move across the surface properly?

No Wind:

  Tyflow_debris_No_Wind.mp4 (Size: 4.61 MB / Downloads: 20,839)

With Wind:

  Tyflow_debris_With_Wind.mp4 (Size: 4.55 MB / Downloads: 291)


Thanks!

[tyFlow]

Use sticky mode (friction 0% or at least less than 100%), not linear spring.

[kysterama]

Hi Tyson, thanks for replying!

I did try sticky ( I tried every combination possible haha) but it introduces 2 new problems for me. This is with friction and inherit at 0%

backstory: I've added a velocity limiter to stop the X and Y influence from the alembic ocean surface. otherwise props slingshot back and forth unrealistically instead of just bobbing up and down. I wish object bind had a way to turn off X & Y influence, that might solve everything in this specific case.

From my tests, when I have the limiter on, wind will not affect the props at all when object bind is set to sticky. (wind node is at the end of the stack)

The second problem with sticky is the props do not collide properly with the static collision objects in the scene. That only seems to work properly with linear or dynamic spring. Its like the stickyness, even at friction and inherit at 0% overides the collisions. (or maybe its the limiter?)

Is there a better way?

[tyFlow]

Any kind of position-modifying operator will interfere with collisions. Object Bind in sticky mode modifies positions directly, so you won't get accurate collisions. The spring modes operate on velocities, so you'll get nice collisions, but you won't get the objects perfectly sticking to the surface because you're at the mercy of whatever forces you assign to them.

You can try using sticky mode and a Push Out operator to ensure that even if a position modification pushes a particle inside your collider, it will still be pushed back out. Also use a Slow operator to dampen X/Y (even to 100%) to mitigate the other issue.

[kysterama]

Thanks again!

Okay, have been running tests:

1st Issue - reducing x/y influence from the ocean mesh
- When set to Sticky (0% friction) neither Limiter or Slow affect the x/y at all.
- When set to spring both Slow and Limiter work as intended
- Suggestion: add x,y,z locks or percentages that work in sticky mode if that's possible.
For example I would love to just set sticky to z surface influence only. I still can't figure out how to achieve this in sticky mode.

2nd issue - Wind causing hovering props.
- I can only seem to 100% solve this in sticky mode.


Thanks for the Push Out operator suggestion, that replaced PhysX shape nicely for the collision issues.

But I'm as yet unable to reduce the x/y influence from the ocean surface in sticky mode.

[kysterama]

Man I wish I could solve this.

I've been trying another approach to check z position against the ocean mesh and re-bind if above a certain threshold, but I feel like a monkey mashing buttons. Is this approach feasible using object bind and a surface test or am I barking up the wrong tree? I've tried so many different combinations with these operators but I can't get it working.

Trying to achieve:
Object bind props to ocean surface -> remove x/y influence but keep z movement from ocean mesh -> wind force objects along surface -> props stick to surface the whole time

Issues:
Sticky won't let me limit x/y from ocean = erratic and unusable props
And spring will let me limit x/y from ocean but won't let me use wind because props don't stick to surface over time.

So I'm either stuck with stationary props that look awesome, or moving props that look erratic and weird on x/y

[tyFlow]

Here's an example scene that might be helpful. It uses the techniques I mentioned above. I also added a Wobble operator to simulate a bit of rotational bobbing.

Also check that your water surface topology isn't changing over time (vert/face counts). That will cause issues.

[kysterama]

Ah sorry Tyson! Couple of videos in the first post but have packaged up a smaller scene: Ocean scene

Edit-> oops, didn't see your post.
I am locked into a phoenix ocean mesh unfortunately so that it matches the displaced PheonixOceanTex displacement at render time

[tyFlow]

Assuming you saw my other (now deleted) post where I asked you to post videos/scenes/etc....yea sorry, I missed what you posted in the OP

I haven't worked with Phoenix ocean meshes. Does their topology change? Even if it does, you can get around that by using tyConform....create a plane with the segments of your choosing above the ocean mesh, put a tyConform on it, raycasting downwards (0,0,-1), and then use that as your particle distribution object.

[kysterama]

I did just notice the vert count from the alembic ocean surface does changes randomly over time, but only by 2 or 3 verts. like one face is appearing and disappearing somewhere at the edge maybe.

I did package up that Phoenix ocean surface in the zip link in my previous post if you're curious. 
it's a smaller replica of my production scene and exhibits the issues I'm trying to solve.
I will try the tyConform to see if that makes a diference

Cheers!

EDIT-> Well tyconform seems to have inherently removed my entire x/y problem! This is very promising so far. Props are bobbing up and down in z only which is exactly what I'm after!

[kysterama]

Big thanks Tyson! The work you're doing here is just simply amazing and I really appreciate your time and help!
I still need to play with making the heavier objects less bouncy, but I'm getting very close to a good shot.

Great tip on the wobble operator



Thanks again!

[d4rk3lf]

That's looking great man.
I guess, you're planing to add some gray foam around the objects?

[kysterama]

Thanks! Yeah, hoping to get a proper full Phoenix sim going in there now it has props to interact with, but this timeline is tight so we'll have to see how we go!