12 COLLISION GEOMETRY
Bring the volume into your DOP network: you can see how to do so at 01:03:10. In the Parameter Editor, make sure that Use Deforming Geometry is checked. The Collisions tab lets you tweak the collision settings: you can see the ones I used in the video. Check the Collision Guide option to display the final shape of the object that will be interacting with the wall geometry in the viewport.