Help Needed With My Studio: AA Problem and Unusual Darker Shadows with Matte Object

[pixela]

Hello,
As I tried to summarise in the titlle:
I have a studio setup. The base object is an Matte Object with alpha= -1
Background Color is white.
When I hit render, I have 2 problems:
1. I have an Anti-aliasing problem with the white background.

2. Shadows are very dark and sharp with the matte object, compared to the shadows on the rendered with the base object not being a matte.

You can see both problems in the renders.
First image is the base object being not matte and the rest 3 renders are base being matte.
Would someone please explain me why and tell me the solution?
Thanks in advance.

[Alan Iglesias]

Not sure about the AA issue, but in the past I have created acceptable shadows on matte objects in Vray by using a max standard light with Area Shadows and then making the shadow look acceptable using the max light's Shadow Density controls (Shadow Parameter Rollout) and Area Shadow Rollout controls (Integrity, Quality, etc.).

-Alan

[pixela]

Thanks for reply. Is this a known issue with matte objects?

[Alan Iglesias]

Is this a known issue with matte objects?

Hard for me to make that kind of call, but I think a few more shadow controls on the Vray lights would be very nice. Of course, great-looking shadows on matte objects by default would be nice too, but if that is somehow difficult to implement, then the shadow controls would be helpful in these situaions. I think many folks just render out a nice shadow pass and comp it later, but it's nice to be able to do things "in camera" when the budget and deadline are tight.

-Alan

[pixela]

I found a solution for the shadow problem. There is a control for brightness under Matte Object/ Vray Properties. When you lower this value, shadows become brighter.

But the AA problem remains.

[instinct]

What value does the Background have ? is it above one ? What are your AA settings ?

[pixela]

Background is White RGB: 255
My AA settings are min:1 max: 8
In a small area I even tried min:1 max:50 but I still had this issue.

[percydaman]

Ive noticed this myself. I usually have to render out a mask pass for the object so I can then separate the object from its matte/shadow to adjust in post.

[pixela]

THanks Percy, that is a solution.
I just wonder if this is an issue of Vray or a mistake I am making.

[fizzgig826]

Are you using Adaptive Subdivisions or DMC? I used DMC and was able to make the alpha less noisy by upping my samples to 3 and 14
In addition i've always had to render the shadow apart from the main pass and then comp it.
-Fizzgig