PDA

View Full Version : Reflection rendering question



Grey_Jay
10-09-2009, 04:45 PM
Hi all,

I have a scene with 2 object. 1 object (client's product) is a sitting directly on top of the other (floor).

The floors reflection is set to 80%, and is successfully reflecting the product.

Does anyone know how I can render the reflection WITHOUT the floor being rendered? I plan on compositing the scene in AE and need the product/object with it's respective reflection, but do not want the floor in the rendering...

...Or is there another "trick" I can use to product this effect?

Thanks all... :lightwave

Sekhar
10-09-2009, 05:35 PM
If you have LW 9.x, an easy way is to feed reflections node output to diffuse shading for the floor.

symko
10-09-2009, 07:49 PM
Can't you just tell the floor object to be "Unseen by camera" in the objects properties. The reflection will still render.

toby
10-10-2009, 11:30 PM
No, if you set it to unseen by camera you won't get reflection, but if you set the transparency to 100 instead, you will.

But if you're compositing anyway, you should use render buffer export and save the reflection channel (Shaded Reflection) to a separate file.

Grey_Jay
10-12-2009, 10:38 AM
Hi all.

Thanks for you replies.

It got it to work using Sekhar's method of adding a reflection node to the floor's diffusion.

Only problem is that the reflection does not render in my alpha channel, so I can't composite it directly on top of the floor. The product has the solid alpha, but not the reflection. (kinda make sense?)

Any suggestions?

Thank again...

dlanimation
10-12-2009, 10:47 AM
tobys suggestion is the way to create a separate channel with reflection info for compositing..
in'utilities 'tab/buffer export.
'if you're compositing anyway, you should use render buffer export and save the reflection channel (Shaded Reflection) to a separate file..
good luck
dl

Sekhar
10-12-2009, 12:04 PM
Hi all.

Thanks for you replies.

It got it to work using Sekhar's method of adding a reflection node to the floor's diffusion.

Only problem is that the reflection does not render in my alpha channel, so I can't composite it directly on top of the floor. The product has the solid alpha, but not the reflection. (kinda make sense?)

Any suggestions?

Thank again...

Since you have the reflection info in the node, you could feed that to the transparency to remove the unwanted stuff. E.g., see below node setup.

http://www.newtek.com/forums/attachment.php?attachmentid=78286&stc=1&d=1255370637

toby
10-12-2009, 01:27 PM
You don't need an alpha for reflections, they are added on top with a 'plus' or 'add' blend mode. If you try it with an alpha instead it may not look right. If you're trying to comp with the the whole bottle and the table's reflection in the same image onto another, you may have trouble getting it to work correctly. Try it Sekhar's way if you just want to get it done, but it's risky

Actually I just posted an example of this -
http://www.newtek.com/forums/showthread.php?t=102775

avkills
10-12-2009, 03:15 PM
What are you doing in AE?

Could you bring whatever you do want the reflection on into LW and make some geometry to front project on to and also reflect? I think this is the method in Dan's book Inside LW 8.5 (I know dated).

-mark

Iaian7
10-12-2009, 05:53 PM
Depending on how you intend to composite rendered elements, there was a similar discussion over on SpinQuad just over a year ago. Medi8or posted a very helpful nodal setup for generating clean raytraced reflections for compositing, bypassing the additive nature of Lightwave's setup, and getting distance information at the same time. I posted a modified node setup for blurry reflections there as well (though I've made a number of changes since then, for various projects, I don't think I have a good sample ready to post right now).

spinquad.com (http://www.spinquad.com/forums/showthread.php?t=17839&referrerid=13367)

Grey_Jay
10-13-2009, 10:26 AM
Wow... thanks for all your replies.

I will be compositing it in AE. I'm playing with the Buffer Export as per dlanimation's suggestion. It works, but I take i will need to export several different sequence?

Until the, I will be trying all the above recommendations.

Thanks again