matte/shadow problem

[thomes]

hi,

i have the problem that i get shadow of a box (in the middle) on a matte surface (ground) where it should not cast any shadow, because a matte object (covering over the box) is actually casting shadow there.
so if i render a matte of this object and layer it with the other rendering i get double shadow in the "yellow" edged part

any tips to get this fixed? vray 2.40.04 maxdesign2013

here the pictures...the yellow part is the "double shadowed" part.

thanks for help
thomes

matteshadow.zip

[svetlozar.draganov]

This is a limitation with the current implementation of matte objects.
You can of course disable shadow casting of the box above but this will also remove the shadows from the main box.

[thomes]

thanks svetlozar, same in vray 3 ?

[svetlozar.draganov]

Yes - it is the same in version 3.x as well.
You can remove the unnecessary shadows by creating a cutout mask with the help of VrayMatteShadow and VrayShadow Render Elements.

For example the Shadow element from objects pass looks like this:

The MatteShadow element of the same pass looks like this:

So if you subtract Shadow for MatteShadow element (you have to apply some color correction to the shadow element) you will get something like:

Then if you intersect the above result with the MatteShadow element for the background pass which looks like:

You will get the exact cutout mask:


Not sure if this approach will work for more complicated scenes.

[thomes]

thanks svetlozar for your big effort !

thomes