Option for double resolution in ZDepth Render Element

[tammo]

I have no idea how difficult this would be to implement but if it is possible without too much effort
it would save a lot of time when you need ZDepth for postproduction.

Right now you have to render each animation twice to get a quality ZDepth channel.
First the standard passes with Anti-Aliasing in your targeted resultion.
And then a stripped down version of the scene at double resolution with the ZDepth Render Element.

The reason for the higer resoulution is that you cannot use Anti-Aliasing on the ZDepth channel.
The same is also true for the color ID channels.

A detailed explanation for the problem is shown in this compositing video tutorial:
http://vimeo.com/10894390 (from 07:30 until 11:30)
or in the Post-DOF plugin manuals like "Frischluft Lenscare".

So a "double resolution" checkbox in the render elements parameters
would be a useful addition to V-Ray i think.

Regards,
Tammo

[jacksc02]

Interesting idea.
I have never had any issues with rendering the Zdepth at the same res as the beauty pass.
The one time I had an issue with a Zdepth pass in fusion was because the saved Zdepth was coming in to fusion gamma corrected but just adding a 'Gamut' node sorted that issue out.

[tammo]

Here is an example with some boxes and DOF added in After Effects with an Anti-Aliased ZDepth pass.
Notice the strange ringing artifacts around the boxes.
Turning off filtering during rendering of the ZDepth pass makes the edges look very blocky.
Your only option is to re-render the scene without AA but with double resolution.

[jacksc02]

What AA filtering are you using on your beauty pass?

[tammo]

I use the quadratic filter most of the time for animations.

Here is a test with a re-rendered ZDepth Channel with double resolution and filtering turned off.
Everything else is unchanged.

The DOF is much better at the object edges.

[Infrared digital]

In After Effects, I cannot get better results with a double sized Z-Depth render. How do you go about applying it in AE ?

[tammo]

If i remember correctly You have to apply the z-blur Effect Inside a larger pre composition and scale that back 50% in your Main comp.
It's much easier to do in a Node based compositor.

[Dariusz Makowski (Dadal)]

How about just burring out slighty ur zdeth pass? Get the AA one and blurr it out a lil bit...

[3DMK]

If i remember correctly You have to apply the z-blur Effect Inside a larger pre composition and scale that back 50% in your Main comp.
It's much easier to do in a Node based compositor.

Seems odd that this would work properly as when you scale a Z-depth image down 50% befor applying the DOF effect as your edges would be slightly smoothed...which would produce incorrect Z-depth values.

I have had good results by simply rendering everything at double resolution [or even larger] without AA ...then resize after DOF has been done. At least this way you results are correct with no artifacts.
The extra time you would expect from rendering double size is offset by the fact rendering is quicker by not having to do AA.

Cheers

[peterguthrie]

I'm with you on this 3DMK, I've tried rendering the zdepth at double res but it really only helps if you render the main pass 2x as well.

[3LP]

I have had that issue also very often.
I also had to render double rez images.
So I'm also with you for that request.

Stan
3LP Team

[trixian]

Using 2x rez for the depth (id etc) pass only works if you use a node based application like Nuke where you can set the depth selection before the rescale occurs, or with a plugin that does this automatically like Lenscare for non node based compositing apps.

Here is a good example of it in action: http://vimeo.com/10895336

[re:FORM]

I've had good results in AE just making a comp 2x res which applies the DOF using the 2x res z-depth channel; ie beauty pass is scaled 200%, dof is at 100%, z-depth is at 100%. You then bring this comp into your main comp at 50%.
Does this actually produce a better DOF or was my satisfaction merely a plocebo effect

[trixian]

Well this would work yes, but you are getting a "filter hit" by uprezing and downrezing your beauty pass like that, but sometimes that might not be so noticable.
What I'd really like was if exr let you store certain passes (depth etc) at 2x res, while keeping the main resolution normal.

[HenrikBC]

I'm complete with tammo on this. For DOF I always render z-depth at double res - and use a double res AE composition to apply the DOF before scaling the result down to 50%.
When I worked on my animated short this was the technique used for every shot requiring DOF - which was most of them.