Hi. I am tweaking an EXR:
Somehow I can not manage to find the way to get everything on top of a transparent background.
I understand the image shows the shadow catcher mixing with a white color, but even if I connect the shadow catcher to the viewer…I will get the shadows on top of white. How can I mix the shadows to the rest of the nodes without adding backgrounds to my output.
Thank you
Most simple way to get shadows in your backplate is to multiply using mix node. There are other compositing methods but that is working good with new shadow catcher. Understanding the math behind each mix/merge operation helps a lot. Math is very similar across multiple softwares.
Blend modes: https://en.wikipedia.org/wiki/Blend_modes
Nuke merge: https://learn.foundry.com/nuke/8.0/content/user_guide/merging/merge_operations.html
Check this tutorial about shadow catcher: https://youtu.be/w70dMniat2M
Thank you! Maybe I was not super clear. What I am trying to achieve is to have shadows and objects on transparent backgrounds and export them as a png. I believe the video you shared is super useful, but he is always mixing the different passes with a background image. I think I managed to do that, but what I want is to always have a transparent background and manipulate shadow and object.
I tried Combined and Shadow Catcher to a mix node. Scrolled all the modes…none of them gave me a shadow and object on a transparent background.
Would you let me know what mode do you use to achieve this?
For 3.0, if you set your your scene but disable shadow catcher pass, render layer will output a RGBA image.
Before 3.0 shadow catcher update you would have to create two layers, one for objects, another for shadow. Problem is that setup will render twice per frame. In your objects layer, outliner tab, right click shadow collection > View Layer > Set as holdout. In your shadow layer, outliner tab, right click objects collection > View Layer > Set as Indirect Only. When compositing you will have two render layers. Second one will output a RGBA image of your shadow, them you can export/manipulate with transparency.
For 3.0 you can also use Luminance Key in a inverted shadow catcher pass, but it’s not the best option. Multiply operation will give better results overall since this new version also has color information.
Thank you. So in other ways, there is no straight way to have a shadow catcher with no color without doing workarounds. It is difficult to understand, for me at least, why the shadow catcher pass isn’t just the shadows on a transparent background.
I find really difficult to output from the compositor tab a render without background. It is really easy if you just save a png render…but as soon as I go into compositor …transparent backgrounds are just headaches.
I saw people using many nodes to achieve a transparent shadow catcher…but I still do not get why the pass isnt just transparent.
Thank you
As a compositor it’s very common to manipulate images to get a desired result. But for softwares like Photoshop it’s normal to use transparent PNG files, yet in professional pos production, that kind of file is avoided because usually generates some edge artifacts. Shadow itself isn’t just black. This is a big topic same way light is.
I did not mean that shadows should be black. Somehow I am expecting to have just the shadows without the “not shadow” area. But of course, shadows are not black. But whatever is not shadow should not be white. I am not a compositor maybe there are advantages to it. I just need to tweak a render in blender and export it without a background…and I do need the shadow catcher pass.
Thank you for listening anyways : )
