3d multipass compositing


Hi All,

1.I am looking for 3d multipass render footage including mattes for practise. I am learning multipass compositing. However i havent been able to come across

much footage for practise.

  1. Also, I have queries about the ID mattes or the matte with RGB color. The queries are
    a. why do we need them?
    b. how do we use them while compositing?
    c. how are they generated?

If you have any link to the footage or footage of your own, kindly help me. It is purely for practise purpose.

Any link to tutorial or knowledge resource about ID mattes are also welcomed.

Thanks & Regards
Jetin Anand


I wrote a whole reply and firefox crashed, so here is a visual guide:


Basically R, G and B values can be used to easily generate mattes to isolate objects. The advantage compared to a B/W matte is you can get 4 mattes in 1 file (R, G, B and A)


Thanks a lot. great resource !

Next to each ID pass there are 3 nodes 1 red , 1 green , 1 blue. What exactly these nodes are doing? Since i am learning fusion i will be doing this operation in fusion.

i got a simple beauty pass & the corresponding id pass and tried something in fusion here is the snapshot.

kindly correct me where ever i am wrong

Also is it possible to find footage with such passes to practice. i really want to practice and learn from my mistakes.



I haven’t used Fusion in a while, but that looks pretty right. Basically you can use the Red channel as a mask to edit your cone, Blue channel to mask your cube and Green channel to mask corrections on your sphere.

As to how you get to those channels, it differs per application. In Shake you can choose which colour channel you want to use as the mask in each node, OR you could use a Reorder node to place the Red channel into the Alpha channel of the image (rgbr) and use the alpha chanel as the mask.

I will try to post some screenshots this weekend.


thank you double supercool.

learning a lot from bankaffairsfilm.com link. really helpful.

looking forward to your weekend post



Hey hey, I just did a post on this over at my other website:


I also have a video tutorial I did for my uni students last year, but it is on another computer so I will have to dig it out. It might be up on Wednesday.


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