Making (spot) lamps affect only one object/material

I strongly suspect a “no” answer to this question, but here goes…

Can I make lamps only affect a single specific object or material ? I know I can make them only affect layers, but that really won’t cut it it this case - I need shadows, and background of the scene is illuminated in a different way (actually several ways) to the parts that need shadows. I suppose I could overcome it by duplicating the whole background, putting it into the layer of shadow lamps and making all the materials “only shadow”, but I’d really like to avoid this as the rendering would be too slow. Any ideas ?

How about rendering the background objects with their lighting first. Then set up the foreground objects with their lighting requirements and render them through the sequencer with the background scene in the, well, background.

Does this help, or am I totally off the mark?

you could use layer lamps for lighting, and have shadow only spots shared on all the layers for the shadow.

Martin

Apologies for the long post, but I want to be clear :

The sequencer idea WOULD work if I :

  1. Knew how to use images in the background when rendering a sequence (could probably figure this out though)
  2. Could get decent shadows from the background objects in question, which bizzarely, I can’t. It’s quite exasperating (it’s doin’ my 'ead in ! (say in a strong Welsh accent)).

Unfortunately this would have the nasty effect of just about doubling the rendering time, which is impractical.

I’m not 100% sure, but I don’t think have spot lights shared on all the layers for shadow will work in this case. See http://rendermonitor.no-ip.com/forum/viewtopic.php?t=18 and wait for the last picture to load. My problem is that I need to have the horizontal beams casting shadows on the walls and floor, but using spotlights that don’t interact with those of the cannons (cannon shadows not visible here, use your imagination) or the TIEs - otherwise the result is not nice. How the heck do I do that ? Have I been tweaking it too long and missing the obvious ?