render layers and masks

Started by Dune, September 23, 2021, 02:45:55 am

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Dune

I never did much with render layers, but I want to render 2 versions of my glacier scene, one fast one in RT (for the distant glacier and water), and another one in PT, without needing to render the (micropoly) glacier and the water, which take up the bulk of time. As it needs to be rendered pretty big, I think this will save a huge amount of time.
So I thought to sink/delete the glacier for the PT render and uncheck the water reflections/colors. The comp them in PS.
But what render layer or pass do I need to check in render layers? I need a mask to cut out the people and veggies and place them in front of the glacier somehow. But the shadows on the ground also need to be there. I don't know if just a depth pass would be enough.
Anyone experienced in this willing to advice me?

Hannes

My advice would be to render the sky and the glacier first in RT. I wouldn't bother with masks at this time, just crop render. You could disable the characters for this.
Then I would disable the glacier, so that there is nothing behind the non ice terrain and also disable the clouds and PT render the rest in RGB and save the alpha as well. If there is no clean cut between the ice and the rest, you could try to apply sort of green screen masks to key them out later.
In the end comp everything together. Just my theory. I don't know, if this helps, but I don't think, there are render layers to achieve this.

Dune

Thanks Hannes.  I thought of this method as well, but cropping is indeed a bit faster again. I did do another depth pass (succeeded now) and adjusted its mask to a very hard one. I think that may work as well to comp in the characters. Just have to try it.

Kevin Kipper

Hi Dune,

There are probably several ways to approach breaking down your scene for rendering with Terragen's Render Layer feature. 

You can use the Clipping distance parameters under the Layer Settings Tab to isolate the background (glacier, sky) and foreground (cave people), perhaps even the midground if necessary. 

You can group your cave people together by selecting their nodes and pressing "CTRL G", and then assign that group to one of the Object Groups under the Render Layer's Objects tab.  This will allow you to render them separately if you wish, and you could do the same for the foreground vegetation too.

For shadow passes, you could add the Shadow Catcher Shader node at the end of the Shaders group and select "Shadow ratio", leaving the rest of the settings at default.  You would need to do this to the shader network for any 3D object you want to be included in that render.  You also need to disable GI, Atmosphere, and the cloud layer's Enable Primary setting, and possibly set the Background object's colour value to white; basically anything that could contaminte the shadow pass which you want to be black and white.  Note that this would be a separate scene.  I'm working on adding some practical examples of this to add to the wiki page: https://planetside.co.uk/wiki/index.php?title=Shadow_Catcher_Shader

Finally, here's a link to compositing the render elements created via Terragen's Render Layer feature:
https://planetside.co.uk/wiki/index.php?title=Compositing_Terragen_Render_Elements

And, Parts 25 and 26 of the Terragen for VFX video series deals exclusively with Render Layers and specialized masking techniques for use in compositing.
https://planetside.co.uk/terragen-tutorials-for-vfx-section5-rendering/

Dune

Thanks very much for your elaborate explanation, Kevin!