shadow only pass?

[ianay]

Like the title says...
Whats the best and quickest way to create a shadow only pass?
As in, just shadows in the end render with transparent bg
Im using LW 2019, I was changing all surfaces to white etc, but there must be a quicker way these days? surely?
I keep seeing shadow catcher appear for this when i search but all the tutorials on it seems to be about compositing but...
I just want to create a shadow pass for use with my other passes in AE

Thanks for all help!

[prometheus]

Like the title says...
Whats the best and quickest way to create a shadow only pass?
As in, just shadows in the end render with transparent bg
Im using LW 2019, I was changing all surfaces to white etc, but there must be a quicker way these days? surely?
I keep seeing shadow catcher appear for this when i search but all the tutorials on it seems to be about compositing but...
I just want to create a shadow pass for use with my other passes in AE

Thanks for all help!

Go to render tab/render properties/Buffers
Uncheck all, and go to the extra section, and check shadows, or just search for shadow, once checked, you will render as normal and in render window you have the buffer dropdown list, from there you will find your shadow pass to save out, but it will be inverted and shadow in white and all the other areas black as transparent, so you have to invert that in post.

Shadow caster is only for when you need a shadow to cast shadows on to an invisible plane or object, so it looks like it is casting a shadow on to whatever background image you have in the scene, but not needed for this case .

[ianay]

Im still getting white on the surface though, the only transparency is with the BG

[lardbros]

Is it possible to post pictures?

The best way is as Prometheus says. Export the shadow buffer, or preview it using VPR. You then use this in compositing app to modify the original shadow colour/shading. Or you can multiply it over the top of your base render (that excludes shadows) and blend it that way.

[ianay]

I wasn't blending with multiply!...
Works a treat now
Thank you all

[prometheus]

Im still getting white on the surface though, the only transparency is with the BG

I don´t follow you..white on surface? do you mean something that is white that isn´t the shadow, the shadow will be white...and that is what to be expected as I mentioned before...and a shadow isn´t transparent at all..you have to use other overlay modes in post, such as subtract or exclusion to turn this white shadow pass to a dark shadow, how strong it is ..you control with opacity.
This white shadow pass will respect the light´s size and softness when producing the shadow, you just have to find the proper blending modes in after effects that you need.

[prometheus]

I wasn't blending with multiply!...
Works a treat now
Thank you all

Oh..great, there are several ways of blending it, depending on what software you use, after effects or photoshop for stills or free krita, exclusion is also a good alternative when working with a still in krita, I do not have acess to after effects anymore so I can not tell for sure what the best option is there.

[prometheus]

and this might be useful from the Lightwave channel about render buffers and compositing, but this with fusion..not after effects..but many principles may work the same with some differences.

[myrtle.rankind]

Useful video. But anyway it have a lot of differences, also I cannot tell principles are the same. Similar yes, not the same