selective light reflection

[Joanna A]

Hi all,

I'm trying to render a simple scene with a metal object resting on a reflective plastic "floor" surface. I'm using a rectangular light to illuminate my scene. I want the metal object to reflect that light, however i don't want my floor surface to be reflecting the rectangular light in question. I just want it to be reflected in my metal object hence the problem when turning my light to invisible as there's no reflection in either.

Is there a way I can do this by tweaking my floor material or else?

Thanks in advance for any input ;D
jo

[Joanna A]

Re: selective light reflection

o! just came accross another thread... should i build my scene on different layers and apply my lighting to the object layer only, not the floor ?? sounds like it should work have to try that.. :P

[iamcapitano]

Re: selective light reflection

That won't make a difference (putting in different layers).

I don't really understand what you really want to do, i mean i understand what you're saying, but i don't get how you came to the conclusion that that is what you wanted?

Turning the rectangle invisible only means that you can't see the rectangle shape, but it still emits the same light.

In order to have nice reflections in your metal object you should use an hdri + rectangle lights. The rectangle lights should be invisible aswell as where have you seen a studio with big flat rectangular bulbs?

[Joanna A]

Re: selective light reflection

I am using hdris ....
but i still want my object to also reflect my light, what annoys me is that my floor surface is also reflecting that same light and i don't want it to... i have a neutral background on my floor material so it doesn't reflect my scene's hdri.
don't worry so much about the light source being rectangular (tho you can have square emitting light boxes in a real studio environment) as the reflection on the object only shows as highlighted strip... but it does show as a square on my floor surface...
basically i do want and need that rectangular light in my scene, i just need to know how to get rid of its reflection on the floor.
as for the layers it's not really a conclusion... just something i thought i ought to waste more time on
jo

[iamcapitano]

Re: selective light reflection

I still don't get it.. how can you have/want a floor to reflect an object on it but not the light that is affecting the object? makes no sense

[Joanna A]

Re: selective light reflection

ok let me explain... the light is shedding light+reflection on the top of the object which is good as it's adding more contrasting colors to my metallic object. the floor reflect the bottom of the object giving the render more depth and realism which is also good. however the floor also reflects the shape of the light and that is bad because you can see the light source and i'm having problems moving it out of my camera shot without affecting the nice reflections i have going on my object.
Therefore i was wondering if there was a way i could have my floor material reflecting my object but not that light...

does that make more sense?

[iamcapitano]

Re: selective light reflection

Oh okay, well, in that case it sounds like your rectangular light is in the wrong position, like studios, there should be one on either side at an angle, and some times one from above (but not directly on top), if it is set up properly, you wouldn't be see the light shapes in the floor with those angles. If you don't know what i'm talking about, look on youtube for some videos regarding studio set ups, there's a couple for vray-sketchup.

[Joanna A]

Re: selective light reflection

ok i'll have a looky thx IAMCAPITANO ;D

[Joanna A]

Re: selective light reflection

on the other hand is not possible to control reflection on materials? ??? in terms of what is being reflected to hide the light source?

[andybot_cg]

Re: selective light reflection

As far as I know, you can't have one material reflect a light while the other doesn't. The reflection is per light (check or uncheck invisible - as iamcapitano explained) and the materials either do or don't reflect. My suggestion would be to render the scene twice, once with the light hidden and once without, then combine the two parts of the image when you're done. You can even add an "material id" color to the material and select the channel to get a perfect mask for one of the materials. (I can explain more if that didn't make sense)
-Andy