Well a lot of slider movements will change the behavior of the rendering engine, and so to ensure accuracy and consistency, it has to restart the render.
At least that's my take on it.

Daniel79 wrote:No "mtl" in this version?

No MLT ever.
http://refractivesoftware.com/forum/vie ... =24&t=3475
But their algorithm hasn't been released in this version either. It's a lot of work, and should hopefully be available in 2.3 final.

EDIT.

Woah. Very cool... Nice geometry and good color choices.

sam75 wrote:does it include MLT ?

No.
You're gonna have to wait a little while more for that.
http://refractivesoftware.com/forum/vie ... 4&start=10

Thanks for the update guys!!

Hi guys,

MLT has never been implemented on a GPU before.
Although many people believe our main competitor has it, they don't, they simply cut caustics and glossy to glossy reflections from the render equation, generating a biased image, without fireflies.

You need to give us some time to come up ...

Hope it's nothing bad. We should send him a card.

Now I won't have to go Houdini->3ds Max->Octane. ^_^