Just a sanity check, does motion blur affect the shadows cast by matte objects? Like would a helicopter rotor cast blurred shadows on the particles?
In order for Krakatoa to use the motion of the matte mesh, you will need to ensure the mesh has vertex velocities.
If you’re loading a mesh from an OBJ file, you will need to provide two time-offset OBJ files. There’s an API call to do so.
If you’re creating a mesh by manually setting the vertex positions, you will need to assign the vertex velocities. The API also allows for this.
The API docs have examples. You can even do non-linear motion in meshes by specifying multiple meshes. There are examples of how to do that too.