G-Buffer object ID is not supported?

[AForestProUser]

Hi,
After 3 days of rendering on a farm, now that I have hundreds of GBs of render data and have spent thousands of dollars when I open the rendered frames to check all channels, I see that all the VrayWireColor, VrayObject ID and all MultiMatteElements are blank or messed up. I mean those of which that do not use Material ID and instead use Object ID. Also wireColor is messed up as it renderes all different geometries of a forest with the same color even though they had separate wires. Please tell me that I have done something wrong and it's not forests fault.

[iToo]

Forest doesn't support Object ID or other channels that depend of the item's ID. In V-Ray Forest is handled as an unique object with its own ID, and it's not possible inherit or assign multiple IDs.

Unfortunately we cannot bypass this lmitation. The only workaround is to use Forest Tools to convert the items to stand-alone instances.

[AForestProUser]

  I'm kinda confused, how is it different from other scatter plugins, while others retain the object IDs? It's surprising forest with some good features lacks to support some major V-ray features and it's mentioned nowhere.

[AForestProUser]

Also now that I test converted some objects with forest tools I can see that their ID's are lost. Do you mean I have to select instances then manually and reassign everything??!

[iToo]

I cannot say about other scatter plugins. Perhaps they use a different scattering procedure, i don't know.

Regarding Forest Tools, you are right: it's not assigning the source ID, although it should do it. Strangely, anyone have reported this problem before.
I apologize by that. Please, tell me your Max version, i will send you a custom patch.

[AForestProUser]

I am using 3Ds Max 2014. I appreciate your effort. While waiting for the patch, I have an idea. Since you use Color ID in the Geometry panel under properties of forest for differentiating the object displays, Could you use it in a way so that at render time those color IDs are converted to something useful to be then used in an element or something as a work around for not having object IDs?
Btw, Is it possible for the patch to instantiate at render time, Since I have over a hundred Forest objects and they will add to dozens of million instances. Having them inside max whether as boxes in viewport or hidden in a layer will kill the viewport performance, not only that, bringing millions of objects in v-ray adds a whole lot to scene preperation before rendering.

[iToo]

I just sent the patch to your e-mail address.

I'm afraid the other changes are too complex for a custom patch. Regarding instantiate at render time, we tried that before writing the shader for V-Ray, and it doesn't work: Max takes a long time to generate thousands of instances in the scene, regardless if they are displayed or not. Also, this technique may have other potential problems.

[AForestProUser]

Thank you for everything. Even though the patch worked, it was not practical. As the conversion of a forest to instances is single threaded it takes 30 minutes just to convert one  relatively complex forest and it ate up all the RAM so the next forest would crash Max. Put that aside, as I used some scripts to convert object IDs to Mat IDs and automatically create elements for them. The Nice but strange thing for me is that this is not the case for Corona. Both Object ID and Material ID work in Corona and Forest, which is great. Is it because of the render engine limitation and how it handles the geometry or is it based on your implementation of the code for different engines?
Thanks

[iToo]

Each engine uses a completely different implementation. In V-Ray, by default each generator object is associated with an unique ID. In the past we tried some tricks to bypass this limitation, but we were not satisfied with the result.