I try to add a "mountain" to make an irregular sphere, but I don't understand why it doesn't work :o I tried to put a "point from volume" to add a lot of points, but same result, nothing happened (I join my file in case you would like to have a look)
There's two things to take in account here : 1. Mountain node is just an Attribute Noise node set to add noise on positions (P attribute) along normals (N attribute). Now that you have points generated by Points from Volume node, they don't have normals, so they will not deform. Either deactivate the "Noise Along Vector" option on Mountain node or transfer N attribute from input geometry to these points using Attribute Transfer node. 2. Flip Source node expects mesh geometry and ignores particles, that why you get nothing after using the Points from Volume node.
when I load your scene I get an error and the scene seems broken.
But if I were you I'd simply redo the setup with " Particle Fluids > Flip Fluid From Object" and selecting a polygon sphere with a "mountain" SOP already added.
And then add the Pigs head and make it a surface collider ( Collisions > Surface Collider )