Matte shadow speed

[YoyoBoy]

I have a simple scene that renders quickly. But when I set the floor-plane's VRay Properties so that it is invisible except for the shadows cast onto it, the scene renders incredibly slowly. Is there a method for doing this that renders quickly?

Thanks.

[nikolay.kusht]

Does this issue occurs on a specific scene or on every simple new one? Is it possible to send us a test scene for investigation.

[YoyoBoy]

Just sent a file to Support. Thanks.

[roboxx]

Hi,
i have the exact same problem here, also tested with simple scene with sphere on a plane, with matte object enabled render times increase by factor 10x to 15x. Any news on this ?
Vray version is 3.5.04

[Alex_M]

I'm currently working on a job that uses matted ground plane and thought why not test this. The scene is really simple and all materials are clay. For me it renders almost 2 times slower if the ground is matte. Is this normal? Screenshots below.

[psanitra]

I`m experiencing same behavior with 3.6 version. Just setting the ground vray properties to Matte+shadows in alfa gets multiple times slower. That`s in advanced version.

In RT, the alpha channel of the matte area it`s getting almost no sampling, and it`s impossible to control the noise lvl. there One can set the treshold to 0.005 and it looks like 0.1
ares that contains RGB get sampled correctly, super clean, but areas with no RGB but containing shadows are very noisy. Looks like the RT sampler not based on RGBA but only RGB. Somebody experiencing similar results?

[Alex_M]

In RT, the alpha channel of the matte area it`s getting almost no sampling, and it`s impossible to control the noise lvl. there One can set the treshold to 0.005 and it looks like 0.1
ares that contains RGB get sampled correctly, super clean, but areas with no RGB but containing shadows are very noisy. Looks like the RT sampler not based on RGBA but only RGB. Somebody experiencing similar results?

Yes, I have this too and wondered if it was just me! It is why on the job I mentioned in my previous post I switched to Adv otherwise I would have done it in RT.
UPDATE: I've created a thread about this problem in the RT forum.