Hydro Pressure - Direction

Hi, I'm rapidly becoming a heavy user of kangaroo, thanks Daniel!

Quick question on the hydro component; how can you change the direction of this force to be inside rather than outside an object? I've tried making the 3 input points cw and ccw, I've also tried making the density negative but the results are always the same.

best,

Brian

Replies to This Discussion

Permalink Reply by Daniel Piker on July 12, 2012 at 3:08am

Hi Brian,

That's odd, when I test it setting the fluid density to negative works fine to reverse the direction of pressure.

Are you sure your mesh has consistently oriented normals ? Maybe try some mesh fixing functions on it

(AlignMeshVertices, Weld, UnifyMeshNormals)

If that doesn't fix it please post the file or send it to me and I'll take a look

Permalink Reply by Brian Loudon on July 12, 2012 at 3:57am

Hi Daniel, yeah, I suspect that is the problem, I've created a handcrafted mesh as I'm creating different zones in a fabric bag, and I want to be able to manipulate the rest lengths and stiffnesses of these zones to form find what I'm looking for. I suspect though that my mesh is maybe not quite right yet. I'll go back and look at it again and let you know. The odd thing is that I've actually got it working with a height dependent gradient to a pressure component. My worry with using that though is that this would be then static to the initial heights of the triangle centres and won't update during the simulation?

Permalink Reply by Daniel Piker on July 12, 2012 at 5:11am

btw - you can use the face normals component to check this. If these arrows all point the same way, then the resulting pressure force should also have a consistent direction.

Oh, and yes - If you define an input to a Kangaroo force which depends on height, this will not update when the kangaroo geometry changes. (which is exactly why there was a need for the depth dependent hydro pressure force).

Permalink Reply by Brian Loudon on July 12, 2012 at 9:53am

thanks for that, yes I've used the face normals now to check things, my dynamic mesh was all facing outwards, but something isn't right in my springs on the edges. I haven't worked out quite what yet though, I've found that if I bake out my dynamic mesh and then apply the pressures it is working perfectly fine, so I think I've made a mess of my datamatching somewhere in there!

I'll try and post something up once I get it working a bit better (or at least so that it is readable!)

thanks again

Brian

Permalink Reply by lingsong Jin on July 13, 2012 at 5:02am