Using Vray Matte Object/Material with refractive objects

[sdesvb]

Hi Guys

I’m have a dilemma using vray matte objects. It’s been a while since I’ve done this so I’m a bit rusty. Sorry if this is a little confuisng. I am rendering an archiviz and am rendering people as a seperate layer. In the past I’ve always made every other object in the scene a matte object that receives shadows/reflections and has an alpha of minus 1. This works fine mostly but the problem I’m having is that when I put a person behind a glass railing, although I can see the bottom half of him in the render, the alpha of the railing cuts him off. I set the alpha back to 1 thinking that this would bring the alpha of the glass object back to normal (grey) but it became solid white. I’ve tried to use a material wrapper on the glass material instead of using matte object and get the same problem. After doing some tests, I’ve discovered that the glass object NEVER has a grey alpha even without a material wrapper nor being a matte object. A did a search on google where I found a tutorial advising to go to the transparent material and under refraction, affect channels choose all channels. This didn’t work either…

Does anyone have any insight into this please?

Vas

[AltoR]

Strange … I did a very simple scene with a transparent pane of glass and a box behind it. If I tick “Affect all channels”, glass alpha turns grey, and stays solid white if I don’t tick it. So it works here … Sorry.

[svetlozar.draganov]

Once the objects is set as Matte objects its alpha has different behavior.
You can still render gray alpha - if you set alpha contribution to something like 0.3 but the objects behind the glass will be still clipped if the material is with refraction properties.
However you can use transparency instead of refraction properties - and the object behind the glass will be visible.

Matte_Refraction.zip (25 KB)