so we actually support point clouds in OBJ but not "implicitely", you still have to define "point primitives". Here is a simple example:
v 9.021 -9.021 -9.021
v 9.021 -9.021 9.021
v -9.021 -9.021 9.021
v -9.021 -9.021 -9.021
v 9.021 9.021 -9.021
v 9.0211 9.021 9.021
v -9.021 9.021 9.021
v -9.021 9.021 -9.021
vn 1 0 0
l 6 7
l 7 8
p (for point) and
l (for line) definitions (where you may also define normals and uvs just as for triangles or generic polygons).
The thing is, by default, you'll probably not see the points in the viewer because we have no specific rendering for point clouds. The trick is to use the emissive channel to make the points visible.
See e.g. https://sketchfab.com/models/d72c69dc598a43f8a7a3689dc011b8e1 for the above model rendered with the following material definition:
(see how the final rendering only cares about the emissive color and not the diffuse one)
Finally, as it seems you're looking for a solution to animate your point cloud, you shouldn't look too much OBJ/PLY solutions as the formats don't handle animation. At the moment we only support FBX animation and Blender is coming (not clear wether Collada animation will be supported soon).
I'd say that maybe your best shot right now would be to try FBX morphing (if the number of particles is constant throughout the simulation)