Render with transparent background, and keep shadows

[robertkollar]

Hi everyone!

I am new to cinema 4D and Corona. I have a pretty basic scene and would like the final render to have a transparent background so the plane is not visible but the shadows casted onto the plane are still there. I would like to replace the original background in photoshop after the render is done. From what I found online is that I have to do multi pass rendering. Can someone please explain to me how to do this and set it up.
I attached the C4D file as well if it helps.
Thank you.

[Beanzvision]

No scene attached that I can see?

[robertkollar]

Hi,

I upload it now again.

[Beanzvision]

Done. I can't save the file for you because I'm using a newer version of c4d and the scene might not open with an older version. However, the setup is super simple.
Create a shadow catcher material and assign that to the desktop (plane), create a sky and put the original mat from the desktop (plane) on that. In the shadowcatcher settings,  change the mode to environment and drag the sky in there, lastly in the shadowcatcher change the alpha mode to for compositing.

[robertkollar]

Oh my god it looks awesome, so beautiful.
Thank you so much! I will try it.
What format did you save it so you can change the background later ?

[Beanzvision]

Oh my god it looks awesome, so beautiful.
Thank you so much! I will try it.
What format did you save it so you can change the background later ?

.png Enjoy! :)

[Eddoron]

@beanz:
you can save the file as long as you don't add anything new or convert to items that don't exist with previous versions.

[Beanzvision]

@beanz:
you can save the file as long as you don't add anything new or convert to items that don't exist with previous versions.

Ahhh! Thanks man I appreciate that. I've been fooled for years! ;)

[robertkollar]

Hi there guys,

I would like to ask you abut  something again. I am trying to render a scene where I have 3 objects (cogwheels) with a transparent background and after the render is done I would like to add in photoshop a 100% white background.
I would like that the  final scene has only the 3 cogwheels the  shadows casted by the  3 cogwheels from the 2 corona lights and that the HDRI sky's reflections are visible in the cogwheels; but I dont want the shadows casted by the sky to be shown. (For this reason I added a compositing tag to the sky and disable seen by GI) And I want to have a transparent background.
My problem is that when I make the final render I get the transparency but everything else the objects is a grey color which is visible when after I open up the PNG file in photoshop and create a new layer under it and fill it with white. I uploaded some screenshots of this.
Is there a way to render what I would like to achieve? 3 cogwheels with their shadows casted by the 2 corona lights and HDRI sky reflections visible on the cogwheels but no sky shadows, all this with a transparent background. And no grey colour in the rest of the scene.
I attached all the files, screenshots where the grey color around the objects is visible in PS and the final render file in PNG. I can't upload the  HDRI file I use for the sky because it is to large, but other HDRI would be fine too I suppose.

Thank you!
 

[Beanzvision]

Did you try turning off cast shadows in the compositing tag? Correction. That's not gonna do it.

[robertkollar]

Yes I tried with turning off cast shadow for the sky in the compositing tag.
But still after I render it in the png the area around the object will be grey color. So when I place it in Photoshop on top of a white layer the white turns to grey.
It’s like a gradient grey that is lighter towards the light but more strong towards the end where the objects are.
I’m starting to think it’s impossible to achieve the effect I want.

[Eddoron]

Try lightmix.

[tacco999]

try uncheck "Occlude other lights" from corona lights, it worked for me.