## of RGB Mattes Tweet

[sohara20]

We are using octane for Houdini on a high end car commercial and the lack of support for an arbitrary number of RGB matte AOV's is crippling, is there something we are missing? We need to assign matte id to Groups not just top level Geo nodes. In Houdini our complex car assets are a abc file contained in a geo node. As of now the plugin can only assign object properties on the top level geo node and not on the geo groups within the node. These low level groups are what separates objs for material assignments, xforms, etc. I can provide some screenshots if this is unclear. If the Octane core had something like this for the wonderful dev- Jaunjo to take advantage of in his plugin that would make our compositors very happy and prevent us from setting up tedious "matte" renders. Even if Arbitrary # RGB mattes was added without the support for groups we would be much better off. Please let us know what is possible for the very near term as this is simple but crucial for the workflow.
Thanks,
Shane

[juanjgon]

The problem is that the Object ID pass, as you can see, works at object level. Octane only can handle one value for each object, and in our plugin all the geometry inside an OBJ node is extracted as only one Octane object, so there isn't an easy solution.

The workaround can be work with the Material ID pass, or try to build a set of OBJ nodes for each group from your source object (perhaps using the merge node, or other workflow). Could be something easy to do with a script, something like this:
http://www.houdinitoolbox.com/houdini.php?asset=25

-Juanjo

[sohara20]

yeah i imagine its a very deep level change to support geo groups in the octane standalone, that script and sugggestion you provided is a good work around but, we still need to be able to output many # of RGB-only mattes.

[sohara20]

Any reason octane cannot output multiple #'s of RGB mattes otherwise?

[juanjgon]

Do you mean save each RGB matte in one file to get a file for each matte?

-Juanjo

[sohara20]

No, I want to be able to output say 15 RGB only- mattes without the need to setup additional renders using the layering system or any other workaround. So with my beauty render i can select something like "RGB Multimatte AOV" Enter the Id's I want to include and each one is assigned a R, G, or B color. just like vray, corona or arnold. If its going to take alot of work we will use the light layers as a workaround until something more elegant arrives.

[juanjgon]

Well, at OBJ level you have the "Render Layer ID" pass. You can't set the RGB color for each layer, but at least you can group several objects in the same RGB matte.

-Juanjo

[juanjgon]

Or you can also use the "Object Layer Color" pass. At OBJ level you can set the RGB object color and group several objects in the same RGB matte.

-Juanjo

[sohara20]

yeah we are aware of these and as of now anything other than red green or blue becomes problematic so we are using a combo of Render Layer Color and Baking Group Id's which only gives us 5-6 matte separations total. Which in production is just not enough sadly.

[sohara20]

in fact the future of all this matte creation is here. https://github.com/Psyop/Cryptomatte , which is now open sourced. I wonder if octane can support this. https://vimeo.com/136954966