Chaos Corona Forum

Chaos Corona for Cinema 4D => [C4D] I need help! => Topic started by: 3dkobi on 2022-10-18, 09:57:34

Title: How to get the correct alpha channel for this problem
Post by: 3dkobi on 2022-10-18, 09:57:34
Hi,
I have a problem in a very complex scene under NDA so I simplified it for the sake of the question - I have 2 objects in the scene and a camera animation (rotating around those objects).
My problem -  I need to produce a render sequences that has only the visible part of the blue sphere visible in the render, and everything else is Alpha - Including the green part of the torus that is in front of the sphere. Like in the second attachment - only what I highlighted should be visible in the render, everything else should be Alpha
how can I achieve that ?
Title: Re: How to get the correct alpha channel for this problem
Post by: Beanzvision on 2022-10-18, 10:45:20
You could try setting the material you want excluded to black in the advanced alpha mode settings. ;)

(https://forum.corona-renderer.com/index.php?action=dlattach;topic=38135.0;attach=173026;image)
Title: Re: How to get the correct alpha channel for this problem
Post by: 3dkobi on 2022-10-18, 13:58:53
Thanks, I'll try that
Title: Re: How to get the correct alpha channel for this problem
Post by: BigAl3D on 2022-10-20, 02:00:55
I would enable the Multipass feature, add a Mask, change to Include Selection and drag the Sphere in that. Depending on how you save it, it could be a PNG sequence with alpha and you're done. You can also use a separate alpha sequence and Trackmatte it out in AE or another compositing app. If you're not sure how to do this, post back and I'll illustrate it visually.
Title: Re: How to get the correct alpha channel for this problem
Post by: 3dkobi on 2022-10-20, 05:03:25
Thanks, I followed Beanzvision advice and it works great