Krakatoa showing up in reflections?

Did a quick search, didnt find an previous post, so here goes.

How would one go about doing raytraced reflections of a krakatoa particle mass?

Let me do a setup, where such a refection would come in handy.
We are in a dark back ally, a monster made of sand is standing in the ally looking mean.
The street is covered with puddles of water.
From the camera’s POV the sand monster should be visible/reflected in the large puddle in front of it.

The way I see it there are two posible hacks that could acomplish this, but if I am missing somthing obvious, then please point it out.

Option/hack 1:
Render a sand monster pass (only the krakatoa particles)
Render out a scene beauty pass, where I have placed a billboard set to be invisible to the camera, but visible to reflections. approx. where the Sandmonster is located.
Next I then load the Sandmonster pass onto the billboard. This way a 2D version of the sandmonster will be raytraced in the water puddles.

Option/hack 2:
Save the sandmonster particles to a Part sequence and place two loaders in the scene.
Ones that load the sandmonster ready to be rendered and another I placed beneath turned 180 degrees, and finally flip around the X axis.
This way two mirrowed monsters is rendered out in the Sandmonster render pass. Combined with a mask pass this should make the illusion possible.

Are there other smarter ways?

Hi Claus,

At this point, your approaches are what I would do too. For reflections and refractions, esp. at a larger distance or when very diffuse, we have always used cards of the particle rendering (even in Superman where we had a shader that could do raytracing of a voxel representation of the particles, we tried to use cards where possible). The flipped PRT Loader is quite smart as it would provide the ultimate level of detail.

We have a wish logged against reflections and refractions via Matte Objects (so one could produce a mirror pass by rendering particles as seen in a reflection if the matte geometry was a raytraced material). When and whether this will be implemented remains to be seen.

Thanks for your reply.