miultimatte and transparent geometry.

[super gnu]

i need a matte of some glass in my scene, but i need it to be

a) invisible in the render

b) cast shadows at about 50% opacity

c) show up as a solid in multimatte.

seems this is an impossible combination.


if i use vray override i can get it 100% transparent, but casting shadows fine. however wahtever i do, if its transparent, the multimatte is transparent too.


this is very annoying!!


any suggestions|? ive tried all combinations of standard materials, vray materials, refraction, opacity, affect channels etc.etc.. cant seem to get the right combination.

[Morne]

I thought I could cheat it by having 2 glass objects. 1 being 50% transparent and creating the shadows (but set invisible to camera). The other to just be normal to create the multimatte. It works, but it messes up the shadow due to the coplaner faces.

For now the only other thing I can think of is for that 1 object use material id instead of multimatte?

[super gnu]

hey thanks for lending your brain trouble is (if i understand your method correctly) is that you have one object set to visible, and 100% opaque in teh scene, to give you a solid multimatte.. however this will then occlude the objects behind it in the beauty pass?



or did i not understand. i didnt try doing a matid pass, as i had to just bite the bullet and render the matte seperately. deadlines are deadlines!


be nice if the multimatte could have an option to ignore opacity? i can imagine its quite common to want a solid matte for a transparent object..

[Morne]

The actual glass (as in the WINDOW) I just copied in place and called it FAKE. The WINDOW I made as per any other window with a glass material, except I set the refraction to medium grey as per your requirement to make it 50% Then I set that object to be invisible to camera.
For the FAKE object I just assigned a normal material (non refractive) and set it to invisible to camera, reflection and refraction. I also tried turning off GI for that object. As I said, it works perfect, except for the fact now the shadow from the WINDOW object is messed up as somehow it stills picks up the FAKE object as being coplaner to the WINDOW. I'm sure there must be a way to overcome this, but it was late last night and I couldn't think of anything.

But yes, you are right. It would be nice to have some setting in multimatte to enable or disable transparency per ID

EDIT: Actually I just tried it again and now it doesnt work. I can't remember what I did last night, but I'm sure you got the main idea of what I was getting at.

[super gnu]

hmm thats odd because i found if you turn anything to "invisible to camera" it wont show up in multimatte either...

[IVOR_IP]

Have you tried sticking the vrayoveride inside a VrayMtlwrapper?

[super gnu]

and what settings to use in the vraymtlwrapper? i cant see how this would help?

[joconnell]

The passes are being drawn from the renderer actually hitting objects so if you've got something hidden to camera or 100% transparent you're out of luck - if it's not making a contribution to the final pixels in the image then you're screwed. The only thing I've gotten working is to make two objects. You have a 100% refractive object for your matte with an ior of 1 so it's not actually bending any of the rays in the scene and thus appears invisible. You set it's material to affect colour and alpha in it's refraction settings so it doesn't appear at all in the RGBA, and turn on affect shadows so it doesn't cast any shadows into your scene. Next you make a second object, give it a 50% refractive material and turn on affect shadows. You turn off this object to camera, visible to reflect / refract and receive shadows.

Matte wise you can now take your multimatte correctly from the 100% refractive object but this will bring up two issues. One is that even though it's optically invisible, the 100% refractive object will mean you need to use the vray_refract element in your passes. The second thing is that vray does early termination when it can on it's renders, so objects or materials that don't contribute much to the final pixels are often sampled less. What you'll see is because the 100% refractive object is optically invisible, vray will do low quality sampling on this and your edge in the multi matte will be a bit rough along the edge. One thing you can do to solve this is up your minimum sampling in dmc to 2 or more to force vray to do a higher quality minimum sample. Anoither option is to add in a vray extra tex element, set it to include only your 100% refractive glass and put in a vray colour map at 100% white (so you get another perfect matte for your glass) and most importantly make sure "consider for anti aliasing" is ticked on - this'll force vray to use that element to guide the dmc sampler and it'll clean up your edges in the render elements.

I've attached a scene saved from max 2012 down to 2010 just for compatibility but the render comes out correctly for me.