Physics question

[SemperAbasi]

Hi everyone.  I was wondering if anyone could tell me how to keep a prim ball from falling through a mesh walkable surface?  The ball rolls along when it hits the mesh and then falls through.  What do I need to do to keep the ball on the surface?  Thanks so much!

 

[Rolig Loon]

Maybe the easiest solution is to make a transparent prim roughly the size of your mesh object and set its upper surface just at or slightly above the mesh's surface, so that the ball rolls on it instead of on the mesh.  In fact, depending on the geometry of your system, you might even save on L.I. by linking the prim and your mesh together.  Make the new prim the root, and set everything else to physics shape NONE. 

[SemperAbasi]

Thank you for the reply.  My "floor" is not flat though it has hills and valleys.  So putting a prim under it will still make the ball fall through if it stops on a high part of the "floor".  

 

[Rolig Loon]

Hmmm.. Is it set to physics shape type PRIM? (Not to NONE or CONVEX HULL).  

[SemperAbasi]

yes physics shape is prim.

 

[Beq Janus]

Has the creator of the mesh floor made a proper physics shape? If you are using Firestorm you can check this by clicking the "show phsyics" (eye) icon while editing the floor.

https://i.gyazo.com/13883e2576f6ad05a2e1d800613ab959.gif

If not then you hcae two choices.

1) make your own floor physics that is a better match to the visible mesh and then make that a transparent prim as Rollig described

2) contact the creator and ask them to make a proper physics shape for the floor. 

Poorly fitted physics shapes on mesh are a significant cause of user problems

This is quite an old video now but it shows the tool being used and how the bad physics causes issues. https://vimeo.com/manage/videos/240771266

 

[ChinRey]

@SemperAbasi

I'm assuming this is a mesh ground and the correct way to make physics for one of those is to use the High model and not analyze.

There are a few exceptions:

• If the mesh has a lot of very small tris you may have to remove some vertices on the physics model to be able to upload it at all. But in those cases you should consider removing those vertices from the visual model too
• If the height of the mesh is less than 1 m, you may have to analyze or simplify the physics model. But I can't imagine that anybody will ever want to make a ground mesh with that little elevation anyway.
• If the mesh is very small, you may have to analyze or simplify the physics model. But again, I can't imagine that anybody will ever want to make such a ground mesh anyway.

Any other way to make physics for a ground mesh is wrong.

[SemperAbasi]

thank  you everyone for the help!