The Vray geometry tag does not correctly influence the decal object.
I used the geometry tag to turn part of my objects into alpha mattes. The decal objects rendered just like normal and were unaffected.
This does not feel like intended behaviour.
I solved this by simply turning the decals off but I still wanted to report this issue.
Hello @corvin_hiller ,
Please note that this is the expected behavior. This way, for example, you can have your background be a street and you add a car. Using the V-Ray decal, you can add a street shaft or road marking. If you don’t want your decal to affect the shadow catcher, you can simply exclude the plane from the decal as shown here.
I hope this is of help.
Peter Matanov opened a discussion in the V-Ray for 3ds Max section of the forum, which you can check here. You can share what you expect to see there. Thanks 
