RenderID

[powerandrubber]

I can't seem to get the RenderID channel to save in the vray framebuffer under "save seperate g-buffer channels". I also tried extracting the channel from a vrimg but it comes out as plain black. (I redowloaded the vrimg2exr utility as suggeseted on the announcement thread) This channel would be extremely useful for photoshop selection. Any ideas?

[panthon]

The render id only gets saved inside a rpf file. The only way i can think of to recover this info is through combustion, using a show gbuffer operator. That way u could save it for using it with photoshop. Maybe After effects could do a similar process, but i don´t really know.

Beware, render id image is quite jaggy, i´m not sure u´ll take any profit from it....

[powerandrubber]

Thanks. I'm curious as to why renderid is listed as supported in the vrayimg2exr converter help file. I was able to successfully screen capture the renderid channel off the vray frame buffer but that will only work for images smaller than my monitor res. And you're right it is kinda jaggy but it would still be useful.

[panthon]

Thanks. I'm curious as to why renderid is listed as supported in the vrayimg2exr converter help file. I was able to successfully screen capture the renderid channel off the vray frame buffer but that will only work for images smaller than my monitor res. And you're right it is kinda jaggy but it would still be useful.

I guess it says it´s supported because, in fact, it is. Vrayimg should be able to store all these channels and pass them on the exr file. Exr files were created to provide a convenient file format to store both high dynamic range and extra channels (much more than u could think of!), therefore it is very scritpable. Rpf files and exr files are quite similar in their conception, but unfortunately, exr is only supported by limited applications, like nuke. I guess u could retrieve this extra channels from exr too, or with further development, from the vrayimg itself, providing that an application created by chaos could do that.

I think there´s a lot of confusion with these channels, because they are all listed in the gbuffer/color mapping section with no distinction at all. Some of them are used to composite the image, so they create physical layers on the hard disk when asked to (diffuse, reflection, and so on), and others don´t exist per se, but must be contained in a larger file format (render id, zbuffer, node id, etc). It would be great to clarify this a little from the GUI.

[vlado]

The render ID channel is an integer channel, not a RGB one; it is exported in the .exr file as such, but usually image processing programs expect RGB channels only and ignore the rest.

That said, in newer versions, the render ID channel has a RGB representation that can be saved as a normal image.

Best regards,
Vlado

[panthon]

That said, in newer versions, the render ID channel has a RGB representation that can be saved as a normal image.

Best regards,
Vlado

Yeah, that´s what a show gbuffer operator does in combustion. It gives u a rgb representation of the channel integer values which u can use as a selection for other layers that aren´t rpf or exr, just using a "gbuffer builder" operator and taking the output from the other layer as source. This way u can benefit from the id selections in a jpg image if u want.

If u can get a rgb representation directly from vray, how does it handle the jaggy edges issues? Does it take into account the coverage as we usually do in post?

[powerandrubber]

Ok that makes sense, thanks for the replies. An even more helpful setup would be a "material name" channel that would create a unique rgb color value for every different material in a scene, not just the material ID which is only useful for multi sub obj mats. Say an archviz client want's all the red siding in a scene to be darker. I could go to the material name channel, select all the red siding and darken it in real time in PS without rerendering. RenderID is close but I would have to make many selections to get all the red siding because it may exist on many different objects.

I suppose a script could temorarily replace all materials in a scene with solid unique self illuminated colors, turn off all lights, and render a quick "material selection pass". Anyone know if that exists?

[panthon]

Powerandrubber, i guess i have a more practical solution to your problem. I ran into similar issues as u are having now and asked for a maxscript solution which would help in postproduction.

You can create a little script which will take your materials into account and will assign a unique object id number to each object with that material.

Example: you have a cube, a teapot, and a sphere, with the same material. You run this little script and all these objects will have the same object id, so in postproduction u can apply effects to all these at once, color correction included. I´ve chosen the object id channel because it benefits from coverage channel, resulting in more accurate selections.

We have this little script at work, but unfortunately, this is an in-house developed tool and I can´t share it. But maybe u can look for something similar in www.scriptspot.com, now that u know the theory. Just a few tweaks and voila! A pity I don´t have a clue about programming..

PD. It doesn´t work with multisubobject material, as it assigns only a number per object.

:P