comping question

[priad]

Here my problematic:
I need to comp some objects on a footage and make them well integrated, I have re-modeled all the footage scene in CG to give the best GI on the objects when I will put them in there, and I need to render a shadow pass like this:

1. shadows from objects on background scene
2. shadows from objects on objects
3. shadows from background scene on objects

And not :
1. shadows from background scene on the background scene

And I need of course the rvb of the objects to comp them on, all in one pass.

How can I do that?????

I have tryied many things and I always have shadows or GI on the whole scene.

[joconnell]

Okay then! For starters you probably have your 3d objects that you want to integrate, and then some rough 3d objects modelled in the shape of your background objects to recieve shadows and also bounce light.

1: Do a render with your 3d objects to integrate turned off to "visible to camera" and your background plate models as vray matte objects with alpha set to -1.0, and shadows turned on. This should give you a pass with the shadows in the alpha channel. You can turn off cast shadows for the background objects too.

2: Use the vray shadow element in render elements.

3. Background scene objects turned off for "visible to camera", normal vray properties and alpha 1.0. 3d objects to be integrated set to vray matte objects, alpha contribution -1.0 and shadows turned on.

[priad]

Does this mean that I must do several pass,
two passes ?
in the first pass you're talking about, I need to render my bots(objects ) and I set them to visible to camera off. and my background set to matte in the vray object properties alpha -1 / shadows on and affect alpha on. This will give me a pass with the shadows in the alpha channel but without the background on background shadows. well
I need to use the shadows element and not the raw shadows elements.

Do I need to make a second render pass???? or I need to turned off "visible to camera" the background and alpha 1 in the same pass?

thank you so much for this great input m8

[joconnell]

Yeah you'll have to do more than one pass to get each of the shadow elements since vray doesn't have any kind of per object shadow passes - I don't think any renderer does in this case.

[priad]

ok right, I have well understood.
thx man!
I keep you posted

[priad]

I think I have a problem with the IES shadows.
The IES don't work with the matte !!!!!!!

[priad]

no light work in matte exept vray light!!!!!!!!!!!!!!!!!!!!!

[priad]

My problem doesn't exist with only vray light.

[jacksc02]

i can confirm that this isnt working.

[priad]

Well, I have found a solution: I have re-made all my lighting and changing the IES in square vraylight in a kind of little box.
I have some wishes for the futur:

1- for any vray light we have visible/invisible It would be cool if we can have a matte thing to check in them, because when I render the visible vraylight they are in the alpha shadows.
the best is to have them visible in rgb and invisible in alpha shadows.

2-to found a solution for the others lights to make them working in alpha shadows.
all work pretty well with the vraylight except the alpha visible.

no need to make many passes to sort out the shadows which is very cool.