Chaos Corona Forum

Chaos Corona for Cinema 4D => [C4D] I need help! => Topic started by: ShynnSup on 2021-11-20, 22:38:46

Title: What is the best way to use Backplates in Corona C4D?
Post by: ShynnSup on 2021-11-20, 22:38:46

I am not sure how to approach this.Maybe there is no 'best' way just different ways but I still wanted to ask for the standard way of doing it...

I understand I can use 2 different HDRIs (can be the same color corrected) one for lighting and one for background. This is easy to do with the checkboxes in Corona Sky object.

But most backplates are planar JPGs:
Should I just use a plane and apply a material with the JPG in diffuse channel and use frontal or flat projection?
Should I use a Background object?
Should I use another Corona Sky object with projection set to frontal? I think this might be the one no?

Thanks

Title: Re: What is the best way to use Backplates in Corona C4D?
Post by: Atlantis on 2021-11-21, 10:18:34

The "official" way to do it is probably via Scene environment. Create a Corona material with your jpg image and drag it into the required field.
Or you can create a Cinema 4D material and drag it to a background object. (although I got some render errors with this method lately)
I still use the C4D method to see the image in the viewport.

Title: Re: What is the best way to use Backplates in Corona C4D?
Post by: Beanzvision on 2021-11-22, 14:48:28

Hi, there are a few steps needed for this.

1. Create a plane object and add a shadow catcher mat to it and add your ''backplate'' image.
2. Add a Corona sky object and assign your HDRI to it.
3. Create a Corona light mat and disable ''emit light'', add the ''backplate'' image to it.
4. In the Corona ''Scene envr settings'' enable ''Direct vis'' and add the Corona light mat and set the projection as ''frontal''.

I hope that helps.

(https://forum.corona-renderer.com/index.php?action=dlattach;topic=34940.0;attach=157159;image)

Title: Re: What is the best way to use Backplates in Corona C4D?
Post by: Anthe.cr3 on 2021-11-23, 05:05:17

Hi

I used the settings Beanzvision shown in this post

however, the aspect ratio is off with this- how to i resolve this?

Output resolution is set to the resolution/aspect ratio of the background image.

EDIT: I see you can edit the Scale and offset in the environment override settings, which is rather tedious, but then the aspect ratio of the shadow catcher is still off.




pls see attached file

Thanks!

Title: Re: What is the best way to use Backplates in Corona C4D?
Post by: ficdogg on 2021-11-23, 10:27:21

I think you'll need to render this in the VFB not in the viewport, the viewport has a more or less arbitrary aspect ratio.

Title: Re: What is the best way to use Backplates in Corona C4D?
Post by: BigAl3D on 2021-11-23, 23:54:54

@Anthe.cr3 Are you saying that when you view your car from an extreme angle, the image no longer lines up with the car? If yes, that is a limitation of using a backplate technique. Looks great if you stay within the limitations of a 2D image.

Dome mapping in v8 daily may give you better results in some situations. Not sure exactly what you want though.

Title: Re: What is the best way to use Backplates in Corona C4D?
Post by: Anthe.cr3 on 2021-11-24, 08:59:27

@BigAl3D

Hi

I did not try to make the point, that the image does not line up with the car (which would be very dumb), but that the Image of the shadow catcher is not in correct aspect ratio, Compared to the corrected aspect ratio of the background image. The car in the second screenshot is not the subject of this issue, it was just there, as i came across this issue during working.

I used the extreme viewing angle, only to showcase that the shadow catcher does not allign with the background image, of which i corrected the aspect ratio.

I downloaded V8 with dome mapping, and it is great for what it does. But when lets say using a larger focal length & trying to render out high resolution renders, corresponding high resolution backplates are the only way to go, as even a 16K Hdri is limited with it's resolution (and some other aspects)


Thanks!

Title: Re: What is the best way to use Backplates in Corona C4D?
Post by: ShynnSup on 2021-12-04, 21:15:50

Quote from: Beanzvision on 2021-11-22, 14:48:28

I hope that helps.

Thank you @Beanzvision, it did!

One small issue tho, the HDRI I am using has a suggested EV of 6. But this totally blows out the backplate. What do you suggest?

Title: Re: What is the best way to use Backplates in Corona C4D?
Post by: BigAl3D on 2021-12-07, 18:36:13

@ShynnSup In my experience, you need to add a Corona Compositing Tag to your ground object and turn everything off except Seen by Camera. I think that's what you need. Give it a try.

Title: Re: What is the best way to use Backplates in Corona C4D?
Post by: Beanzvision on 2021-12-08, 15:34:47

I think you could also try adding a Tone Mapping shader to help control the exposure?
https://support.corona-renderer.com/hc/en-us/articles/4402738012689--Corona-Tonemap-Control-Map

Title: Re: What is the best way to use Backplates in Corona C4D?
Post by: ShynnSup on 2022-01-10, 23:31:38

Hi Bengamin, thank you, that helps!

I recently stumbled across another rock :(

The Global Volume environment completely changes (dissaturates) my backplate, is there away to stop the environment from having an effect on it?

With environment ON:
(https://i.imgur.com/kOFip2o.png)

With environment OFF: (correct)

(https://i.imgur.com/pfvgz9B.png)

(https://imgur.com/e3b9a6ef-1800-4191-b14f-0d9effb4749d)