Vray Matte Issue

[abs]

Hello,

 

I am sure people have faced similar issue and I want to know your workaround for this problem.How do you render people and cars in architectural walk-through/animation in separate pass ?

The way I started is

--I rendered out the main sequence.

--I've place cars and people in the scene.

--Select whole scene except cars & people, & turn them into matte objects via Vray properties.i.e. by checking 'matte object', alpha contribution to -1, 'Shadows' & 'Affect alpha' checked.Of course I can achieve this by applying VraymtlWrapper but I want to this way for now.

--Rendered the scene & I face 2 issues.

 

Issue 1) All cars, people & their shadows have blue tint on them because of Vray sky which i can fix in post but is there a solution to this ?

Issue 2) When cars & people are under direct sun their shadows are OK but when they go under shade of a building or tree they still cast harsh shadows on ground as if building or tree isn't there.

 

To make you understand it better I will explain it in a simple scene.I've created simple plane as ground, a wall and 2 boxes as people ( one in shade & other under direct sun).Both boxes are on the right side of the wall and I've placed sun on left side so that wall would cast shadow on one of the boxes.

 

Attaching 3 images.First image '01.png' is the pass of 2 boxes (see the box under shade is creating harsh shadow like there is no wall),

--second image '02.jpg' is what I am getting after compositing 01.png and main scene,

--third image '03.jpg' is what I want to get as final result after composting.

 

I have tried to find various solution like rendering ground with the cars and people.I got the shadows right but for some reasons the rendering become very slow and alpha of the rest of scene is somehow got affected.To counter this, I switched off 'Recieve GI' of rest of scene.The rendering time & alpha got fixed but image was very dark which was expected.

 

So what is your solution ? what process do you follow ? Am I doing it right ?

 

 

Thanks in advance,

 

AB.