Render only one material?

[marcobaccioli]

Hello everyone, hope I am not posting a "new but very old" topic. My goal is to render an interior scene, as the sample below, being able to re-render *only* some materials several times (say for example, the floor), without needing to re-render the whole scene. In other words, is there a trick to render the floor, replacing the parquet with tiles for example, but hiding all the other elements?
ps: while writing down my question, I feel like the answer is no! But maybe you can suggest me some undreamed-of solutions

[A2Zen]

- change a kernel to deep_chennel_kernel
- choose type: Material ID
- lets it render for 2000 s/px
- copy the render to clipboard
- Photoshop: FILE->NEW and paste the render
- you can now make a selection of every material easily by the magic wand tool

[gordonrobb]

Depending on why you want this, I would like this too. I find it would be useful to render 'elements' of the scene, either by rendering only one surface or rendering an area of the image. I want this for setting up materials better. But that might not be why you want it.

[Refracty]

a render region feature would definately help here

[bepeg4d]

and what about a render region masked by id materials numbers?
ciao beppe

[marcobaccioli]

That's the point! Yes A2Zen, you can work with post-production in Photoshop using material id pass, and I use this feature quite a lot... However, what I am looking for is a way to render a specific element (say a couch for example) with different materials (re-calculating the material specs as reflections, refractions, etc.) without having to re-render the whole scene, avoiding hours and hours of rendering just for one single material change...

As I can see so far, there is no way ( Thanks guys!
Marco

[Refracty]

If render region would be ready then you could at least combine that with the material ID pass in post and select the specific render region out of the rectangular region.

[marcobaccioli]

That's right Refracty, that would be good enough to save time on renders and isolate parts I want to render more times..

[kavorka]

I think the problem with the just re rendering a certain element is that the lighting and color of the surrounding objects is based on that object, so if it was a bright red, the surrounding scene will look different than if it were a white couch.

Because the way Octane works, I can't see them really trying to implement this any time soon.

However, a render region feature will obviously do almost exactly what you want. Just need to make sure it doesn't crop the image, but keeps the overall size with a transparent PNG so you can easily composite it.

[Refracty]

I think rerendering a specific object / material should not be a problem with unbiased rendering because it is like render region with a non rectangular shape. But if you wanne hide things and still showing shadows or reflections it gets tricky...