RenderID Render Element keep changing colors

[AbeTJH]

I've noticed that when using the RenderID render element for masking in the VFB that the colors would change randomly in between renders. This would make an adjustments that I have masks on, incorrect and I would have to redo the masks each time it happens. Its a minor annoyance.

Is this a limitation of this render element?

Are object ID and Material ID immune to this?

I don't want to use cryptomatte because it can't be used with IPR or progressive rendering.

[hermit.crab]

Adding new objects to the scene does rearrange the render id's internally, indeed. I will speak to our developers about this, maybe we can do something to resolve the issue. You may use the MultiMatteElement as an alternative, though you need to set either material/object ids manually.

EDIT: Sorry to say, this is how the Render ID works.

[^Lele^]

Yes, renderIDs are variable, as they are implicit and get shuffled around (even between frames...) by Max itself.
Use material or object IDs instead, as those are explicitly assigned (and default to 0) and won't be changed by Max.

If your job is quite massive, i am sure you could find some script to help you create big amounts of multimate render elements from nodes selections, for example, as material or object ID.

[yavor.rubenov]

Hello,

Another option is to use the "Use node handle" option in the VRayRenderID element - node handles are unique IDs assigned by Max for every object in the scene. They don't change when adding new geometries. The only issue with them is if you use X-Ref scenes.

Best regards,
Yavor

[AbeTJH]

Interesting, thank you for the work arounds. Will test them out!