View Full Version : Speaking of Depth...

05-24-2004, 01:43 PM
Can anyone put Depth Buffer AA into perspective? (note the new feature in render options?)

Since AA will put grey between black and white data, it screws up depth info, but you don't want jaggies either. Is this new button a solution?

05-24-2004, 02:32 PM
That option was there before as a plugin I believe. It will only work in some situations and I can't recall the specifics. I think the real solution would be with the coverage buffer but I'm not sure if that is working or not. I had talked to an Eyeon rep about it in the past and he seemed to indicate that there was a problem on their end with AA in RPF files. Not sure if other apps handle it better or not.

FWIW here is from the LW7.5 docs

Depth Buffer Antialiasing

The Depth Buffer Antialiasing command (Effects command group) has been added to specify how the Z buffer values from multiple antialiasing passes should be combined when creating a final depth buffer for output. Executing the command will display a small dialog. The Minimum Value setting (the standard behavior) causes each pixel to store the closest of the depths found at that pixel in all passes. The Average Value setting causes each pixel to store the average of the pixel's depths in all passes.

05-24-2004, 03:17 PM
It doesn't really 'smooth out' AA passes, just averages them out - still not pretty.

The best way to get useable depth renders is to oversample - render the depth buffer at 200% size and scale down in your compositing app.

This works fine in AFX.

FYI, NT seemed to have fixed the RLA & RLF export formats, so that Object IDs and Material IDs get exported properly - so in theory you can key out any Object or material without having to render separate passes.

Well done NT

(Yes, I don't moan ALL the time)


05-24-2004, 07:24 PM
That is what the Eyeon rep recommended, to render at twice the resolution and downsample in DFX.

blabberlicious, does the coverage buffer not work in AFX either? From what I've read about RPF that is supposed to handle the AA but I guess it isn't implemented consistantly.

05-25-2004, 12:35 AM
I did quite a bit of testing of the format, which you can find here:


Material and Object Id's work, but the Coverage buffer is meant to help mask out materials/objects that aren't picked out well. Again a bit hit & miss. Best avoided.

I did some tests after LW8 arrived, but for the life of me can't rember what the conculsion was about AA and oversampling. I THINK we decided that blurring the 100% Depth Map looked fine, but the Object and Matreial Buffers needed to be rendered at 200% to avoid nasty non alaised edges when keying stuff out.

Rats! I'm going to have to go back and remind myself.

I'll post back later today, and look into coverage too.

05-25-2004, 02:52 AM
Here's a LW8 RLA Export at 100%, Medium AA. I have Keyed out the Jacket, but you can see that the edges are Non Alaised.....The Blue fringe is the background colour (blue) creeping into the matt.....

05-25-2004, 02:54 AM
With COVERAGE applied, the Background bleeding is corrected.....

Much nicer - but still the edges are NON ALAISED

05-25-2004, 03:14 AM
Here's an RLA Export at full resolution with Depth Buffer applied and The jacket Keyed out and coloured.

As you can see for quick DOF, the buffers it produces are fine.
But if you were using the Depth buffer to composite an Image behind a pre-rendered scene, then you would probably want to render the depth at 200% size, because the non-alaised edges will not be masked by the blur.

Sorry if this is obvious and a bit of topic, but it's interesting, and a good way of getting flexible keying and quick DOF quickly..... :-)

05-25-2004, 03:31 AM
Here's the Depth map rendered with the RLA export, used to Drop a Graphic behind Object (how cool is that?).
You can see that the NON alaised edges are much more obvious. Feathering doesn't really help (at all).

So, what have I learnt?

If you want clean matts of surfaces & objects, or create clean Depth Maps, it's probably best to render 200%.

If you want quick DOF 100% resolution is fine.

Lastly, beware: As you can see, the Material ID is picked up on reflected surfaces too - useful, so be wary if, say, the skin of character is reflecting the surface of another object. You run into problems because the render treat the object and it's reflection as one 'surface'.

It gets messy!

Now, back to work!

05-25-2004, 03:38 AM
.. just a quick Q blabberlicious.. is is the .RPF format an "image saver" in LW8 or is it still an image filter with export properties.. ?


05-25-2004, 04:00 AM
Take back what I said!

You don't have to render a Depth Map at 200%, just use the AFX EFFECTS>MATT TOOLS>SIMPLE CHOKER tool and the Jaggies are gone!

Oh Joy! I'll be begging clients to change stuff post render now!

Didn't like the idea of oversampling if I could help it!

JonnyX: I still use the Image Filter Export, as it gives you control over what buffers get exported.

05-25-2004, 06:02 AM
oh! - does that mean there is an .RPF image exporter now yes, yes please yes...?

05-25-2004, 08:43 AM
Thanks for all the screens, very helpful! Will save me a lot of experimenting.