Chaos Corona Forum

Chaos Corona for 3ds Max => [Max] I need help! => Topic started by: Fireside Dreams on 2021-05-28, 17:59:27

Title: [Max 2022] Excluding object from Direct Lighting / Backface Cull for lighting
Post by: Fireside Dreams on 2021-05-28, 17:59:27

(edit: apologies for double-posting, I was logged out halfway through modifying the first post, and accidentally clicked 'new post')
Hi there

I'm trying to render a scene where the roof is not directly visible to the camera, but is still used in calculations for indirect lighting etc. Effectively this illustrates what I'm after.

(https://i.imgur.com/Sc0rEoP.png)

However I'm getting issues with the lighting, where the floor / walls / anything under the roof isn't receiving direct lighting, making the scene render black (although the correct objects DO shop up in the alpha channel.

I've constructed a demonstrative scene to highlight the issue.

I've constructed a green 'room' and a blue 'roof'. Direct and Indirect Lighting passes shown

(https://i.imgur.com/bwEU0Ml.png) (https://i.imgur.com/SwjUYVd.png)

As you can see, the shadows fall as they should in direct lighting, and the green room has a slight blue halo around the centre from where the 'roof' resides.

However so far all attempts I've tried at rendering the green room, without rendering the blue roof but keeping its indirect lighting, have failed.

So far I have tried:

• FrontBack Opacity Switch on single side: Results in the image below. White for front face, black for rear face. In direct lighting the shadow is still rendered as if the opacity wasn't set to 0. Interestingly, if both sides are set to low opacity (second image, 0.5 for both sides) then the direct lighting changes accordingly

(https://i.imgur.com/9hiMNyy.png)(https://i.imgur.com/eEdYSzj.png)

• Untick 'visible to camera' in Object Settings: Roof turns invisible, however it casts a shadow in direct light as if it were visible; indirect light does work
• Exclude from Corona Camera: Effectively removes it from the scene. Indirect lighting doesn't reflect the roof at all, as it's hidden

[li]Ray Switcher: Material hooked up to all nodes except direct: Functionally the same as unticking visible to camera. Indirect lighting is correct, but the invisible geometry still casts a shadow in direct lighting
[/li][/list]

I'm at my wit's end trying to figure this one out - any help would be greatly appreciated, cheers!