Antialiasing doesnt work in certain render elements

[vraypixel]

Hi everybody. I have noticed that antialiacing cant be switched on for some passes like VrayMtlID, VrayObjectID and such. Is this a known problem?

[joconnell]

No, it's not a problem. Similar to the depth channel, the problem is that a pixel can only hold one value at a time. If you've got one object in front of another object, the soft pixels along the edge is the anti aliased combination of both objects so if you've got something like a depth channel or object id then which object does the pixel belong to? Normally you get the object that's in front but unfortunately in this case it's not possible to have an anti aliased edge that works for both objects. The only solution would be to render double res, do your compositing and then scale down to the final size which will add in a certain amount of anti aliasing or with some compositors that are good with scaling, render your main passes normal size, then render the object id passes double res. You scale up your render to 200%, do all the object id compositing work, then scale back down to 100%. A lot of compers like Nuke and autodesk composite are smart enough to know that if you scale up to 200% and back down to 50% that the two scales cancel each other out and you won't lose much, if any quality.

[vraypixel]

How come can the antialiasing than be applied to a VrayZDepth map? Plus the Element is not antialiased even if it is not behind another object.

[joconnell]

No idea but again when you get to a post situation, it doesn't work or make any sense to have a pixel try to belong to two objects.

[vraypixel]

In case of doing still images it doesnt really make any differance. I just want to be able to correct some colors in post and still have smooth edges.

[joconnell]

Unfortunately the only way to do this properly is using the multimatte - it's the only one that gives you really pure edges. Try something like http://www.scriptspot.com/3ds-max/sc...automultimatte as a way to automate it.

[vraypixel]

Tnx Ill give it a try!