What is the workflow of creating mattes in CG scenes?

[LudvikKoutny]

Hi,

I currently need to render a render pass of a character inside a fully CG interior scene. I need to have a pass of just the character with its shadow and reflection component rendered on black for compositing. If I select everything else than the character, and make it matte, then the lighting on all of the matte objects gets extremely simplified to the point where even shadows are not generated, so the bright sunlight outside now illuminates all of the surfaces inside, because it's not shadowed by the walls of the room, and illumination of the character ends up completely wrong. If I just render matte of the character using selection mask, then I am not getting all the necessary components, such as shadows, GI and reflections in RGB and Alpha channel.

I remember this used to work, but I can't remember how.

Thanks in advance.

[Svetlozar Draganov]

What is the status of No GI on other mattes option in the Matte Properties?
If it is enabled then it is normal to have different illumination on the character since matte-surfaces won't interact with each other.
This option should help to get the correct illumination over the character.

I'm not sure however if there is a way to get the correct shadows since once you make everything matte outside lights will also affect shadows in alpha channel.

Let's see first if No GI option fix the illumination and then you may send us stripped down version of the scene and we'll see if there is a way to handle shadows as well.

[LudvikKoutny]

What is the status of No GI on other mattes option in the Matte Properties?
If it is enabled then it is normal to have different illumination on the character since matte-surfaces won't interact with each other.
This option should help to get the correct illumination over the character.

I'm not sure however if there is a way to get the correct shadows since once you make everything matte outside lights will also affect shadows in alpha channel.

Let's see first if No GI option fix the illumination and then you may send us stripped down version of the scene and we'll see if there is a way to handle shadows as well.

I will give it a try as soon as possible. Thanks! I've completely missed the checkbox as I've never touched it before.