Render same Cloud in different Groups

Started by kent_m, June 05, 2024, 02:18:04 PM

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Hi Terrageners,

I'm setting up a workflow that requires different outputs from one 'base' cloud look rendered in different ways - lighting, atmosphere.

The first thing I'm wondering - and I'm just starting to look into this and haven't yet found anything in the docs or by digging within the program so just I'm asking here as well, maybe a bit prematurely (thanks in advance for any pointers  :) )  

I'm using Groups to feed into Render Layers, of course, both for the clouds and lighting. My initial question is if I can have a cloud setup exist outside a group but feed into a Group via a node?

Thanks again



and... I just discovered the NULL node, which seems to do what I need, with a caveat, so let me update/change the question, with a bit more description...

I'm setting up a scene wherein I want to develop an sky 'look' that will then be split into separated renders, all of which require the Atmosphere & Enviro Light to be disabled.

So - using a Null Node I can pipe the clouds into separate groups - but - because of the flow design of the node system - atmosphere pipes into clouds pipe into clouds and finally into the Planet - I can't develop a base look in one group and then separate clouds into different renders without having the upper nodes appear in the downstream nodes.

I'm now looking for a Null Node that would accept multiple inputs of different kinds, Atmosphere and Cloud nodes. Is this possible in Terragen?

Basically what I think I need is a sort of 'Merge Shader' that merges 'Main Inputs'

Kevin Kipper

Hi kent_m,

The Null Shader node only has one Main input.  It accepts and passes through whatever it was given without changing it.

Cloud layers are associated with a planet node.  If you want to isolate cloud layers for a render, you'll have to associate the Cloud layer with another planet node, then use the Object Groups of the Render Layers to make the planet and its associated cloud layers visible or invisible.

For example, add a new planet to the project, then add a cloud layer to the project and pipe it into the new planet's atmosphere input.  Make sure the planet is in a group; you can group it to itself.  In Render Layers, assign the planet group to one of the Object Groups and set the Render parameter accordingly.


Thanks for your reply.

If I understand correctly for what I'm doing then I think the Planet node is not the issue, as I do have multiple Planet nodes feeding into different render layers via groupings.

What I need to is to find a way to get the same cloud layer into the two different Planet nodes, only one WITH the Atmosphere enabled, and one with the Atmosphere disabled. 

Kevin Kipper

I think you would have to duplicate the cloud layers within the internal node network of the second planet.  You can select the cloud layers and copy them, then open planet 2's internal node network and paste them there.  Then you can enable/disable the atmo node for the second planet, or enable/disable its primary/secondary parameter checkboxes as needed.


Yes thats currently the method  :)

I'm look for a way to not have to duplicate the cloud layers, but have all render derive from one node stack. this is to simply a workflow and eliminate potential errors etc.

Thanks very much for your replies


Reposting this because some messages were lost over the weekend:

I think you can feed the cloud layer into multiple planet atmospheres so you won't need to duplicate the cloud layer, only the planet and atmosphere. As far as I remember, the only limitation is that both planets must have the same size and position, but that would be the case here.
Just because milk is white doesn't mean that clouds are made of milk.


Thanks for your reply. 

Yes we've set up multiple Planet nodes and feed them into different render layers via different groups, but the problem we're facing is that because Terragen's node flow is (naturally) down we can't render a cloud stack in a render group/layer without the atmosphere calculated in if its set up that way - which we do in order to develop the beauty look before splitting out the non atmosphere outputs. 

Because of the output requirements we have (to render some of the clouds render with no atmosphere and we want to split out different layers of clouds) we're faced with the problem of having to duplicate the cloud stacks into the different groups. Ideally we'd not have to do that in order to simplify the workflow and avoid potential errors.

If we had a node that allowed multiple Main inputs to composite together or a node that allowed certain inputs to switched off in stream then we would be able to split layers of a single "dev stack" into the different groups with out the higher nodes factoring in to what we want to get out of the lower stacks.

Hope this makes sense!


I may not understand this correctly, but what if you move the atmo node down to be the first before planet (or last one going down)?


I think I understand now. The ability to disable Planet Atmosphere nodes in some render layers is solvable with the existing tools, but that's not the only thing you need. You also need different sets of cloud layers in different render layers. Depending on what combinations you need, sometimes the only way to do it is to duplicate some nodes. If I understand correctly.

For future versions of Terragen (TG5 or TG6) we have thought that maybe cloud layers should be standalone objects. In effect they would just be objects with volumetric materials. This would allow them to be put into groups just like any other kind of object. But there are also some drawbacks to this approach.

I think we could make Terragen do what you want if we had a volumetric merge shader. You mentioned a merge shader that has multiple main inputs, but it would be functional enough if it just merged two shaders like the existing Merge Shader because you can chain multiple merges one after the other to include as many layers as you want.

I will look into this and see if we can make that work. Perhaps we can make some tweaks to the existing
Merge Shader to allow cloud and atmosphere nodes to work through it. That would be consistent with the original design choice of cloud layers being just another kind if shader (a design choice which we have deviated from in some ways).
Just because milk is white doesn't mean that clouds are made of milk.


Dune: ! Thanks! Hah, I didn't even think of that, and YES that does work to allow to keep the Atmosphere out of the render layers that I want it to not render in. Atmosphere had always been plugged in at the top so I didn't even think to try it in a different position...  Thanks for the lateral thinking moment! ;D 

Unfortunately though I would still need a 'Main Inputs Compositing Node' in order to separate the two cloud groupings into different renders...

Matt: "You also need different sets of cloud layers in different render layers"
Yes, exactly. A Merge Node that allowed for multiple Main Inputs would work great for what we need as we could develop separate cloud 'stacks' and then pipe them both collected into the 'test' beauty render group and then ALSO into the separated renders groups.

Thanks very much for your attentions