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Compositing help! how to render only reflections
show user profile  jareu
Hey everyone, i need to render just a reflection by itself so that i can composite onto footage inside premiere. I want to save the rendered file to TIFF image with an alpha channel so that that everything except the reflection will be invisible.

Enabling relfection render element will still give me the Plane doing the reflecting

any ideas?

He who says it cannot be done is interrupting the man doing it.

read 1252 times
8/2/2009 8:20:58 AM (last edit: 8/2/2009 8:20:58 AM)
show user profile  LoyHogg
You want the matte shadow material.. Not sure if its just for later versions of max but it's now called the matte/shadow/reflection material. apply that to whatever you need and check receive reflections.

Not sure if that's all you have to do (haven't got max open) but give it a go..
read 1224 times
8/2/2009 10:58:08 PM (last edit: 8/2/2009 10:58:08 PM)
show user profile  jareu
thanks alot, ill try using that :)

He who says it cannot be done is interrupting the man doing it.

read 1208 times
8/3/2009 2:19:06 AM (last edit: 8/3/2009 2:19:06 AM)
show user profile  jareu
hmm anyone else done this before? i seem to be stuck, tried using matte/shadow/reflection material but not sure where to go from here

He who says it cannot be done is interrupting the man doing it.

read 1198 times
8/3/2009 3:00:15 AM (last edit: 8/3/2009 3:00:15 AM)
show user profile  LoyHogg
Have you got it to just render reflections? Now just render you image sequence as per usual. ?
read 1188 times
8/3/2009 3:26:16 AM (last edit: 8/3/2009 3:26:16 AM)
show user profile  mrgrotey
thats not going to provide him with a reflection pass though is it? if everything has a matte shadow material then there wont be anything to reflect?

I dont think its possible to get a reflection pass without rendering the scene first, one of those stupid 'features' in max.

[edit] I think I read it wrong, ignore me

read 1185 times
8/3/2009 3:32:26 AM (last edit: 8/3/2009 3:33:56 AM)
show user profile  LoyHogg
Mmm.. Maybe I should have tried it before I made such a bold statement...

Rendering---> Render Setup---> Render Elements---> Add.(Reflection)

Try that method...
read 1175 times
8/3/2009 3:48:54 AM (last edit: 8/3/2009 3:48:54 AM)
show user profile  jareu
yeah but problem with the reflections render element is that it still doesnt store the reflections separate to the object with the reflective surface hmmm

He who says it cannot be done is interrupting the man doing it.

read 1168 times
8/3/2009 4:16:16 AM (last edit: 8/3/2009 4:16:16 AM)
show user profile  LoyHogg
Does it not render both? I mean a full render then once that's done you get a reflection pass in another render frame, so you end up with two?
read 1166 times
8/3/2009 4:18:42 AM (last edit: 8/3/2009 4:18:42 AM)
show user profile  jareu
yeah that works alright but onces saved as a tiff file, the alpha doesnt make that reflective object invisible. There must be an easier way to composite reflections onto video footage, what method does everyone else normally take?

He who says it cannot be done is interrupting the man doing it.

read 1161 times
8/3/2009 4:42:10 AM (last edit: 8/3/2009 4:42:10 AM)
show user profile  soontekk
you can set a render element to render and save a reflection pass but you have to render the whole scene.

however, you can modify your scene to render a lot more quickly without visibly changing the reflection pass

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read 1146 times
8/3/2009 6:19:56 AM (last edit: 8/3/2009 11:28:12 AM)
show user profile  Jollabollathan
I tested using a matte/shadow material to receive the reflections, but, stupidly, it seems that the alpha doesn't work properly with it: it either has completely transparent alpha, despite receiving reflections, or completely opaque alpha.

It seems the only workaround is to render a seperate pass with the reflected object 100% self-illuminated white, and set to be invisible to camera but still cast reflections, and everything else black, and use that as a luma matte in comp.

read 1121 times
8/3/2009 3:13:12 PM (last edit: 8/3/2009 3:15:49 PM)
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