hey.
i got a problam with my project. i try to render only the shadow withe AOV but after i render it out it gets color from the dome light as what i understand and it’s not black and white ... i dont know how to pass it i need the dome light in.. please help
pic of the shadow pass after render https://drive.google.com/drive/folders/1AzAuOuVaLMnJHwItOryBMSjqvCCLeGUe?usp=sharing

Hi shelibartov12,

Please share a project file; you can replace your model with a simple object to keep it small.

Images have very little information compared to a Project file.

All the best

hey you help me again thank you!
so here is the project
https://drive.google.com/drive/folders/1iq-vo5V3FTCtr0LKM4rxKoDKH2OzIkmk?usp=sharing

Hi shelibartov12,

Thanks for the files and the extra work. Especially for using a well-known cloud service.

The Dome light has an image in it there. That image sends color and light out and tints so the shadow area. The Shadow pass is a mask, so it is inverted.

If you render to the Picture Viewer, there is an Invert option in the Filter area; then, you can see what the shadow would look like if not presented as a mask. As it is a dome light, it will be soft.

The tip here is wrong (!), but if you need it black and white, desaturate the image. Again that is not correct. But the mask can then be used to limit a Color Correction to tone the area down.
I assume you know that, but since I write in a forum, shadows are most likely not black in natural life. They always have light from something in it, like the sky, clouds, and bounced light from somewhere; even humidity influences that.

Is this answering your question?

If in doubt, use a simple scene with two objects and one light source and explore this.

All the best

P.S.: Here is my colleague, who is highly knowledgeable in Redshift 3D guiding through this
(it is in Maya and Nuke, but the core ideas are the same).
https://vimeo.com/268393168

tthank you for your time.
my goal is to render the shadow in the floor saparately for compositing and better control in after effect..  so i still not sure how i do it

Hi shelibartov12,

Here is a tiny little file showcasing how I handle shadow masks. I mentioned “how I do it” as there are many other options. To use it as a mask is just one option, in conjunction with the Adjustment layer in Ae.
Experiment with Hue/Sat/Value, or check out blend modes. I have discussed Blend modes here on Cineversity.
Here is the smallest setup I can think of as an example. A cylinder on a plane, with an Area and Dome light.
https://www.dropbox.com/s/qf9ksqorpwn8pae/CV3_S26_drs_22_RSac_01.zip?dl=0
Click on the adjustment layer and then adjust the curve. This is a simplified set up, ACES parts are left out as the “mechanic” of the compositing were the target here/

My idea is, as mentioned, to have saturation and value working on it, eventually, Hue, if you like to adjust the shade of it, also here via mask.

If you want powerful control, you need to know all the parts that matter in your scene. Without that knowledge, you follow a cookie-cutter procedure, which limits your ability to work in the way you like.
Without Global Illumination, that was an easy task.

What you need to do is to get more into AOVs. Render, you Beauty pass out. Then explore all the parts of AOV that would lead to composing the Beautypass. I have no idea to make that learning process faster.

This will allow you to see everything that AOVs deliver and what is light, shadow, and GI, besides all the other influences.
Each project might create a different mix. Some do not need other AOVs. One of the key ideas here is that it is not that simple to decide what is shadow and what is light when it is a mixture of several light sources, including EVERY surface that bounces light – becoming so a light source by itself.

All the best