Matte background problem - Urgent

[manlioesp]

Hi I'm working on a project and I'm facing a problem.
I show you a simplified scene.
I'm lighting my scene with hdr and two area lights with disable shadows. Everything is ok but as soon as I turn the matte area lights shadows appears.
How can I avoid this?
I'm in a rush so thanks for any suggestion.

https://www.dropbox.com/s/3v9h75g8ggtfuc9/1a.JPG?dl=0

https://www.dropbox.com/s/858fpyew28mn5mj/1b.JPG?dl=0

Octane version 2.16.2
Direct Lighting Diffuse

[atome451]

Curious... Maybe it was a bug in 2.16.2. With 2.22.2 test3 it works fine.

But, your shadows in your sample are very hard edged (it's unusual with a HDR light) then it's maybe not shadows but the rear of your lights. In this case, you should disable the camera visibility and/or set the opacity of your lights to zero.

EDIT : Oooops, sorry, i did not understand your problem correctly...

[manlioesp]

Thank for your help.
Hope there is a fix for this, but seems that also in 2.22.2 behave the same.
Basically I want to brighten up some parts of my render using lights (hdri dosn't work in this case) without affecting shadows in the shadow catcher plane.

[atome451]

I think it's normal that you see shadows. If you put a gray on your ground, you'll see these shadows. Matte doesn't take into account the color of the material, only the received shadows. That's why you can't remove then this way. Have a look to the render passes in the latest versions to find a solution to this.

[manlioesp]

I try to explain better.
If I use only HDRI I have this clean matte

https://www.dropbox.com/s/je9qezbdvm8aw4e/2a.JPG?dl=0

but if I add also a light in the center of the object the matte is not working for me even if I disable shadows in area light

https://www.dropbox.com/s/4ig3llsx3kmquqz/2b.JPG?dl=0

Thank you again for your help.

[atome451]

Visibility parameters in the area light aren't about projected shadows from the light itself but projected shadow by the light panel itself (the polygons of the light object). It's the same parameter than visibility tab in Octane Object Tag. Unfortunately, it removes shadows from every light sources (environment and light) for the object with an Octane Object Tag, then it's not a solution for your problem.

[manlioesp]

Ok thank you for your effort. Now it is more clear to me.

[manlioesp]

Just as info, is this achievable with multipass in the latest version? It is possibile to separate shadows from different sources? I haven't time to test it.
Thank you

[atome451]

I don't know what you want to do but it's possible to create light passes.

By sample, for this kind of main render

You may create these passes by sample

For this sample i've added an object tag on the cube with Layer ID defined on 2 (all objects without specific layer ID are defined by default to be layer ID 1). In Render passes tab of octane render settings, i've checked ID1 and ID2 in Infos passes > Render layer mask. I've also checked in Lighting passes: Ambient light, Light pass 1 and Light pass 2.

In my object manager i've defined one of the Octanelights to Light pass ID on 2 in his tag.

I hope this will help you a little bit.

[manlioesp]

For this project I was able to avoid additional area lights, but anyway I will investigate more for future projects.
Thank a lot atome451 for your help and examples.
Regards