Material ID and Object ID Masks

#1

I am totally new to Nuke, but see potential in a node based workflow, so I am trying some simple composting with it…however I am having some problems with masking.

I usually use the Material and Object ID passes from Maxwell or Vray to mask different parts of my images in Photoshop, but I can’t seem to figure out how this is done in Nuke 8.

I found the plugin IDselect_hub.gizmo, but it is outputting a slightly different size format, which is smearing pats of my image and I can’t seem to reformat it correctly.

Is there a native way to do this in Nuke, without plugins…is this a correct workflow for a compositing tool like Nuke…I imagine it can’t that different than keying out a green-screen, except using a custom color, but I can’t figure it out.

Any help would be great!

aaron

#2

a gizmo is nothing else then a group of nodes. to see the nodes inside you can hit the “copy to group” button on the gizmo and open it up
then you can see what is used to select the IDs and use this for your workflow

regarding the different format after the ID selecting: is you Comp setting correct (base format?) i believe that the gizmo you use is using some Constant nodes or something which will use the default format of the comp and not the input format of you loader

and selecting the IDs is nothing more then a special key, you could use a keyer and select one color in your ID pass to generate the Matte, but you should be aware that ID passes are most of the time without antialiasing and will get you some fringing on the edge of the matte

#3

As pingking says, the objectID and matID passes are not antialiased. If you need an antialiased matte from VRay, you can use the multimatte element to assign an object ID to each color channel in a pass. Although each element can only provide mattes for three objects, you may have as many multimatte elements as you like.

In Nuke, you can then use the channels from the multimattes just like any other mask channel.

I have never used Maxwell or received a render from it, so I have no guidance for that.