Compositing help needed...

V-Ray for 3ds Max V-Ray for 3ds Max :: General
1

Hello all,
I’m currently working on our company’s first vray project and, thanks to this forums’ great info, things have been going really well. However, I’m trying to render out 2 passes and composite them but I’m missing something somewhere as it’s just not working for me. We will be using After Effects.

Here’s the scene setup:

Pass one: buildings, terrain, rpc environment, trees hidden.

Pass two: trees only, rpc environment hidden, all buildings and terrain set to matte object in vray props, matte checked, shadows checked, affect alpha checked, alpha contrib set to -1, all other settings to default (color back, 1, 1, 1, 1, no gi on other mattes checked)

I have tried rendering the tree pass out with both a black and a white background with drastically different results. I guess my first question would be what color is the right one?

When I try putting the passes together, the trees either come out all black or they are about 50% transparent. Or if I try to mask out the background using the alpha of the trees, I get a large white ‘halo’ around the trees.

Lighting was done with IrMap/LC. AA is Adaptive QMC 1,4. Color mapping is linear 1,1. Clamp off, affect background on.

Here is a link to my source images rendered out.

http://www.westlundconcepts.com/vray/composite/

If someone would be so generous as to take a look and clue me in to what I’m doing wrong, it would be GREATLY appriciated.

Thanks again,
Matt

2

Hi Matt,
Not sure if this is what you’re getting or not, but this is what I get using your “buildings - frame 2701” and “trees - black” frames.

As you can see, the alpha seems to be working ok. Is this what you mean by the trees coming out black? I suspect they are rpcs, and they often do come out very dark, so I usually render them out with the Scanline renderer, with the self illumination of the rpcs ramped up (sometimes to 100% - I think default is 55%). Then you can tweak the levels in aftereffects to tone them down a bit and integrate them into the scene effectively. Bear in mind that rpcs are pretty crappy and never look great.

I hope I’ve answered your question - apologies if I’ve been no help whatsoever!

Andrew.

3

Wow, Ok, that’s exactly what I COULDN’T get to come out. Do you mind sharing what you did to achieve that result?

The trees are actually Onyx. This is the first time rendering them and we are going to make sure the client likes them and their location before we tweak the textures do a good lighting pass on them (that’s why they look bad).

Thanks for your help!

4

Don’t know how familiar you are with after effects, but all I did was import the two images (CTRL+I), drag them both onto the timeline, making sure the building image was in the layer below the tree image layer, and after effects will automatically pick up the alpha channel in the trees.

Glad to have helped.

Andrew.

5

AE will ask you when importing what style of alpha you want. if you dont see that pop up then it means there is no alpha. Sounds like your in need of help as to which premultplied setting to use

6

Thanks for the help guys.

I’m only the 3d monkey, but I wanted to make sure I was rendering it right so our AE guy would be able to put it together correctly. Of course, he’s out sick today so I was trying to mock this up in PS so I could send the job to the farm. And as i’ve learned, Photoshop isn’t a good substitute for AE. Glad to know I’m doing things right in the end, though.

Thanks again for all your help.