MultiMatte Element: new include/exclude in 2.4

[DanielWichterich]

Hi, I am curious how the new feature is supposed to work? As I exlude objects I get strange results: the picture isn't RGB but red, yellow, magenta...

I was hoping for objects not appearing in the rendering at all. But that does not seem to be the case.

[rivoli]

the picture isn't RGB but red, yellow, magenta...

that's how the element is supposed to work, it gives you proper mattes for the selected objects that you can extract from solid RGB colours and the respective channels.
I'm still on 1.5 so I don't know how the new include/exclude feature exactly works, but I guess it's inherent to the element itself, and not to what is actually renderable.

[vlado]

The multimatte include/exclude lists allow you to be more flexible when defining groups of objects that should be included in a given multimatte element. It turned out that people often need a single object to appear in several different multimatte elements where objects are grouped based on some criterion. For example, if you have a scene with two houses, you might want a mask for each house separately; at the same time, you might want a mask for the window objects, and another one for the walls etc. This is not very convenient to set up when all you have is one object ID per node in the scene.

Best regards,
Vlado

[LarsSonparsson]

But shouldnt the element have full r, g and b channels anyway? Not yellow or magenta. I thought that was the Daniels problem in the beginning.

[vlado]

But shouldnt the element have full r, g and b channels anyway? Not yellow or magenta. I thought that was the Daniels problem in the beginning.

If you exclude an object from the red channel, but leave it included in the green and blue channels, you'll get cyan, for example. Nothing prevents an object to be present in more than one channel at the same time.

Best regards,
Vlado

[LarsSonparsson]

Ah, ok. Now I get it.
Thanks.

[DanielWichterich]

I thought that was the Daniels problem in the beginning.

Excactly, but now it is clear!

Edit: I thought it was clear, i tried and it doesn't work as I exspected: Objects on the left is ID1 Object on the right is ID2. Result is in the middle. When I exclude just the little blue box from red I get the result on the bottom. Why is that??

[svetlozar.draganov]

Hello Daniel,

Thank you very much for your feedback.
I'll report this bug into our bug-tracking system.
According to my tests - it works correctly if "include" option is used - but in exclude mode something strange happens.
First all objects are added into include list automatically - and then only specified objects are removed - thats why you have yellow objects into the third image - if you activate only red channel you will see that they persist into red channel as well , and moreover the excluded object is still there.
It works a little big buggy - and it should be fixed - for now it works fine only with "include" option.

[vlado]

The idea of the "exclude" list is not to remove objects that were initially selected by object ID. The object IDs and the include/exclude lists are completely and utterly independent. They both define, independently of each other, a set of objects that will be rendered into the respective channel.

Best regards,
Vlado

[DPS]

Would it be possible to add an option to include and exclude objects but for t to work differently:

Include will only consider these objects for the multimatte, so you could re-use material IDs. You could also exclude objects that are giving odd results e.g if a gradient ramp had been used as a mask.


I think this would be a cheaper way to control your blend materials than render mask for whole objects that has already been partially masked by another.

[vlado]

I'm not sure I understand; can you post a few examples?

Best regards,
Vlado

[DPS]

I will when I'm hooked up to the Internet.

But here's an example: Say you have used material IDs twice for different shaders on two objects. The objects have blend materials.

This would allow you to create two multimattes, one including object 1 only and, the other including object two. And these would respect the masks used in blend materials so the result would only ever be RGB, no greys if you added an objects to all channels.

Also you could easily exclude for example xrefs that may have doubled up with MatIDs.

I hope that makes sense. otherwise I'll post an example.

[vlado]

Hmm, I see. But this is only a very specific case; you might want to do the same thing for object IDs, or combined object ID and material IDs and exclude lists... it can get infinitely complicated. At the same time you can do that by generating a couple more render elements and multiplying them in post, no?

Best regards,
Vlado

[DPS]

I could, but I have five scenes xreffed into one, if I wanted three per scene then I'd have to set up 15 file paths and manage those files rather than nice tidy multichannel exrs.

I can do though, it was just a suggestion.