Is it possible to break apart cloud renders?

[Matt]

That sounds like it should work. Can you send us a .tgd?

Make sure that the planet node isn't drawn with a double white box around it. That's a warning that means it hasn't been captured by the group it appears to be in.

Matt

[Oshyan]

For those who might come across this thread in the future with similar questions, the problem ended up being that the second planet node was not "captured" by the group that had been setup and linked to the Layer for separate output. This is indicated by a white outline around the node that is not "captured" (even if it is technically in the area covered by the group). We know this is somewhat unintuitive behavior and we're looking into improving it in the future.

- Oshyan

[dorianvan]

Yeah, Matt told me that the planet wasn't "captured" by the Planet test group, so it wasn't part of the group even though it was inside the group's area (ie. bright white line box drawn around the node in the Network View), easily fixed by either dragging the node out of the group and back in again, or by right-clicking on the title bar of the group and selecting "Group: Capture Nodes". And the new planet should only have the cloud connected to it, not atmo, or anything else. Also I needed to un-check "render surface". For GI he recommends rendering a GI cache on the scene that includes both planets (i.e. no need for a render layer), and use the same cache for all layers so that lighting-wise they all fit into the same environment.

Further, he said that for the cloud render layer, under "All other objects" to set Render to Holdout and enable Cast shadows and other rays. When rendering the layer with everything some settings are reversed. You'd plug the "cloud" planet group into Object Group 1 as before, but set that to Render Invisible. For "All other objects" you want to Render Visible and enable Cast shadows and other rays.

What I'm trying to figure out now is probably simple but now sure which file format/setup will give me an alpha like what a png does.

[Oshyan]

Thanks for providing the details here. Alphas are rendered out into separate files. They're chromatic, so they have unique info in the R, G, and B channels, but you can combine those 3 together for a traditional alpha I believe.

- Oshyan

[dorianvan]

Thanks for providing the details here. Alphas are rendered out into separate files. They're chromatic, so they have unique info in the R, G, and B channels, but you can combine those 3 together for a traditional alpha I believe.

- Oshyan

How are alphas rendered out into separate files? I don't get it.

[Oshyan]

Check the "Extra Output Images" box. Alphas will be saved as separate files as long as you use "Render All To Disk" or "Render Sequence".

- Oshyan

[dorianvan]

Yes, I knew that thanks. I suppose I wasn't clear enough. When I open up the rendered elemen files in Photoshop, they don't have the png-like background. So I can put it in-between layers. I must be doing something wrong.

[cyphyr]

You should be able to create an alpha channel using the cloud depth render layer. It will match the cloud RGB and alpha.
Tip, set the "Far clipping distance" to something much less the the default 1e+016, maybe as low as 10,000.

[Oshyan]

Yes, the alpha images do not themselves have transparency because they represent the transparency chromatically in all 3 channels. Flatten the image to grayscale then copy the result into the alpha channel of the image you want to mask.

- Oshyan