blurry mmre

[max montana]

hi there,
when doing post in photoshop i often realise that i need a mask i havent thought of when i did my rendering, then i want to render with lower settings as i only need the mmre, but face strange prolems by doing this.
depending on what i do i get blurred areas on some(not all!!!) edges of some(not all!!) masks.
in the images below you see that the mask for the facade is just fine, also rendered with low settings(low preset 20/20_0,01), only on the edge to the jaloisies i get a blurred area.
when i rise the seetings(medium preset 50/20_0,005) its much better, but this results in high rendertimes.
when i uncheck shadows i get the same problem, but on the edge of another object and don`t know why.
so can someone tell me why this happens and what i can do to get fast renderings only for mmre`s?

[rivoli]

the sampling for the multi matte element depends on your render settings. so well, you should re render the scene with the same setting you used for the beauty pass. unfortunately there's no workaround for this, render elements are, as vlado says, side effects of a rendering.

[vlado]

What rivoli says is true; I only want to add that the multimatte element exactly matches the part of the object that goes into the final render - the mask is always correct in that particular sense.

Best regards,
Vlado

[Preisler]

Have you tried Rendermask?

http://www.tepavicharov.com/scripts.html

Preisler

[max montana]

thanks for your replies, i hoped that there is a workaround.
will try rendermask, looked at the video and it seems to be promising, thanks for the hint preilser.
one workaround(but timeconsuming)could be to add max materials to the objects i want the masks of, and make render elements with scanline.

[muoto]

A little off topic, but...

Hmm...in the rendermask tutorial movie, there is a Trees Collection V2.00
What is that ? where to get that ? Any ideas ?

Thanks