Help Understanding This

[leejk]

Hi,

First, let me say that tyflow is the hardest thing I have ever had to learn. It really defies logic in that when something works in one place it will most likely not in another place, at least that has been my experience so far. No amount of tutorials seem to help either, as I always run into a unique situation that has no immediate answer.

For example, please see attached. I am simply wanting to fill a bucket with particles and dump it. However, the particles fall right thru the bucket. I have a similar setup in another scene, and it works, but not in this scene. Can someone take a look at this and please explain why???

thanks

[tyFlow]

Your bucket is using convex hull as the PhysX Shape type, but it's a concave object. You also assigned non-overlapping groups to your cubes, so they have no way of colliding with the bucket anyways.

Remove the groups and set your bucket to a compound PhysX shape. Grid slice mode will probably work best for the bucket shape. You also have starting penetrations set to "ignore" everywhere. That's going to cause any cubes touching the bucket on the first frame to fall right through it.

[leejk]

Thank you for explaining the "why"! That has been my challenge... there is lots of videos on how to do something but almost none say why you need to do things.

This was a very good video on PhysX Shape: https://www.youtube.com/watch?v=puHGAyue8Ic
This gentleman has some very good videos on tyflow that go into the "why". I have not been realizing how critical that setup is.

I was not really paying attention to the shape type. I was trying to re-use an approach that worked in another scene digging dirt, but did not work in this one, which was my frustration.

I had to use the mesh hull type to get the best results. In this situation is that not OK?

BTW, it would be helpful if the display hull option had a way to shade the hull. The wireframe can be misleading for newcomers.

I think I found a bug maybe... when you right click a value field to bring up the context menu and the time slider is on any frame other than 0, it triggers a sim refresh. It seems it should not do this.

[d4rk3lf]

I was not really paying attention to the shape type. I was trying to re-use an approach that worked in another scene digging dirt, but did not work in this one, which was my frustration.

I had to use the mesh hull type to get the best results. In this situation is that not OK?

Try to understand difference between convex and concave shapes. 

https://contenthub-static.grammarly.com/...Convex.jpg

Sphere - convex 
Torus - concave 
Box - convex 
Tube - concave 
Pyramid - convex
...etc.

So, it probably worked in your previous scene, because the shovel, or whatever object you are using to dig the dirt was more of a convex shape, then it was concave. 
Default PhysX collisions are convex (because it's faster), and if you are using concave object (like the bucket) it will just apply convex shape for collision on top of it, and automatically close holes (and curvatures). Just be aware of that. 

Nowadays, TyFlow have few methods of dealing with concave shapes, but in the first releases there were only convex collisions, so workaround was to brake concave shape to smaller parts with voronoi, link them all together, and then it would work fine. 

Hope this clarifies a bit.

[leejk]

Nowadays, TyFlow have few methods of dealing with concave shapes, but in the first releases there were only convex collisions, so workaround was to brake concave shape to smaller parts with voronoi, link them all together, and then it would work fine. 

Hope this clarifies a bit.

Yes it does, as it was an older scene I was refering to and it was doing exactly that.