Hi all,
I’m having issues with the vray shadow catcher.
I have a job where I am compositing some furniture into a photo of a room, very simple, or so I thought!
I have modeled the basic room, matched the camera to the photo, got the light setup, and added the furniture in the room. I have selected the room/floor etc and clicked the “vray shadow catcher”, when I render its almost like its not recognising the room and its allowing the sunlight through into the entire room.
The sun should only come through the opening in the walls, but then i make everything matte/shadow the sun then comes through the walls and illuminates all my objects.
I hope that makes sense, its hard to explain.
Ive set up a much more simple scene to test and the same issue is occurring. Here’s a link to that scene - Unique Download Link | WeTransfer
Can anyone explain what is happening here? Am Imissing something really simple?!
Thanks
I should have said, if I light the scene with plane lights then it all works fine, but if i use a light outside the windows like a vray sun or a direct light then I get this issue.
This (the lighting affecting the objects, even though they are in the matte object’s shade) is controlled by the “No GI on other mattes” option (which causes the object to appear as a matte object in reflections, refractions, GI, etc. for other matte objects) and is active by default. It happens with regular lights, too, if they are strong enough.
Now, to get what you want, you may disable it, but this will complicate things, because there will be GI on the matte object itself (unfortunately, there’s no method of excluding GI on a per-object basis). Since you don’t have objects in direct sunlight, I think simply disabling the VRaySun will suffice in your case; the result will be only GI shadows from the VRaySky (this sky could also be placed as a VRayDomeLight texture instead of in the Environment for it to have some lighting effect).
What if you place the reference image directly as a Background in 3ds Max (screen projection)? To keep the VRaySky’s effect, you should add a VRayDome, place it as a texture, and make it invisible.
That didnt really change much, the render/alpha are still not right. Its very odd.
What I meant was to do the comping in 3ds Max itself. If the background is the original image, the GI/GI shadows that are cast on the matte object itself would at least be placed on the original image (not a VRaySky like your last screenshot). When “No Gi for other mattes” is disabled, such an Alpha is expected and correct (matte self-cast GI shadows/ GI correctly captured by the same matte).
What you could also try is to set the GI amount of the VRayMtlWrapper to 0 (which will leave out only the GI shadows). Of course, you can play around with the Brightness parameter for a better match.
im using vray gpu and the ‘No GI on other mattes’ doenst work.the cpu does but gpu it behaves like the option is turned off. This is using V-Ray 7, Update 2 Hotfix 1