Simscape Multibody: How to model spatial contact between two objects using point clouds?

Hello Everyone,

I'm trying to get the hang of using point clouds around geometry to model contact behavior/forces when objects collide. Right now, I'm starting with a simple model: a sphere dropping from a height onto a sphere fixed in space. I have a point cloud surrounding each sphere. I want to use Spatial Contact Force blocks (or some other method) to explore the collision between the two bodies.

My first foray into using point clouds was dropping two cubes with points on each corner onto a Grid Surface. This was fairly straightforward and I was able to see what I expected, which was a dice-on-a-table kind of effect.

I seem to be having trouble, however, connecting things together to model object-to-object interactions, such as the spheres I described above. Generally I am running into errors such as " 'Spatial Contact Force1' is not connected through its B port to a valid geometry. Resolve this issue in order to simulate the model." I have tried a few different combinations of connecting the Spatial Contact Force block, adding a Spatial Contact to each sphere, etc.

Am I missing something? Perhaps mis-applying the Spatial Contact Force blocks? Another method entirely?

Any suggestions would be helpful! Screenshots of model setup and block diagram attached.

Thank You!

[Jongil Lee]

Dear Kylen

You need to modify the one of ball from your model as below. The Spatial Contact Force block need the contact between a pair of geometries in 3-D space.

https://www.mathworks.com/help/releases/R2023b/sm/ref/spatialcontactforce.html

[Kylen]

Thank you. This works for simple shapes, but is not as effective for complex shapes, due to the convex/concave geometry described here: https://www.mathworks.com/help/sm/ref/spatialcontactforce.html

Do you have any suggestions on how to use this or another method for geometries with concave areas? My intention with the dropping spheres was to practice with simple geometry before moving to more complex items. From my understanding of the spatial contact force description at the above link, I don't think using the "entire geometry" option will always work well with complex shapes.

Thank you.