Volumetric lights!

[mr-bojangles]

Hey people,

Hoping someone might help with a lighting problem I have!
Basically, In my scene I have a spot light, and two poly grids. One grid is placed directly above the second one, and the spot light is positioned so that it's rays hit the top grid (however the spot lights beam is illuminating both grids). What I want to do is apply a transparency map to the top grid so that the light passes through this grid (where transparent) and hit the second grid below it. So far so good. However if I give the light a volumetric property, turn shards on and turn shadows on or off, the vulmetric light doesn't work correctly!!! By correctly I mean the shards appear to stop at the first grid, and not continue through the transparent areas! I s this a limitation with volume light? It works fine if a delete polys on the grid, but not if there is a transparancy map (procedural or painted) on the grid!! I can't model the grid as I want to have a cheap caustic effect by using textures................anyone got an idea. Maybe a fast light node plugged into the spotlight, and have a texture drive the caustic effect? (have tried this, must be doing something wrong as it crashes soft 2.02 everytime!).

Any ideas greatly appreciated! By the way I'm trying to create a sea bed render (which has to be animated!)

[richard-sher]

Is this what you are trying to do?

If so, then you need to chek the "Transparent" box in the volumic property editor.

[mr-bojangles]

Hi Ed,

Thanks for the reply, it was much appreciated. Yes this is the kind of thing I was looking for, and after turning on 'transparent' in the property page I did see a difference. However, I have found some other problems. For instance to actually create the transparent areas on the grid, I had to use a painted texture and copy it's alpha to RGB. I had to turn off 'force shadows' in the volumetric page, and instead turn on the spotlights shadow attribute.

At this point, I had an image which looked somewhat like yours.....great. But I did find that turning on shards in the 'volume' PPG and trying to animate them was a problem, as for some reason the shards still appear to stop at the first grid, and continue through to the transparent areas stipulated by the texture. Basically u can see the shards animating above the grid, but not below....ever had this problem? Maybe I could use invisible objects floating around the scene to create my own shards?
My last favour, is whether it is possible to use a procedural texture as a transparancy map......doesn't seem to work for me....is it possibly because I need to extract an alpha to plug it into the transparency of the material node?

Sorry about the amount of questions, maybe one day I can return the favour? (I hope!)

Thanks