How to Save rendered depth files as rgba

[amitc]

I want to save the depth file as uncompressed RGBA
or may be as "tiff"
Maya by default saves it as "iff". Is there a way to get around this???
The docs does say that it is saved as rgba but I am not able to read "iff" files except from Fcheck utility

Please suggest

Thanks
--Amit

[noe]

may be there are other workarounds, but I use photoshop (7) and have saved me some actions. There is a batch function in ps 7 so you can easily convert your iff depth files to the format you need.

[amitc]

Thanks for that tip.

I am not sure how it'll work,
as z depth is stored as float (1/z) . Conversions might change it by casting them as int(255*(1/z)) , etc

Can PS 7 do depth compositing of images with depth info of several such images?

[noe]

I can send you my PS action. 1. It selects the alpha channel with the z-image 2. deletes the unused rgb channel and converts the picture to a greyscale tiff file

You can't use PS to do real depth compositing (at least I don't know how to do) But you can load this channel as a selection and blur your rgb image. I always use it in aftereffects in combination with the compound blur filter. But there is a Photoshop and aftereffects plug-in which can do what you want: "lenscare"
http://frischluft.com/

[amitc]

Thanks noe.
I am going to check out the lensflare and your PS action once you send me that
(Thanks! ). This is not exactly what I am looking for though.
Well I am in the middle of writting a z compositor using Imagemagic API and I figured out that z values are not showing up correctly and hence my code is not working.

My question still remains how to save depth files as "rgba" directly from maya. Looks like its not possible.

all thoughts are welcome

[joojaa]

Its possible allright... but if you convert z to RGBA then its not true z depth! True zdepth is:

A) supposed to be antialiased (a point can not be in betewwn two spaces unless the objevcts actualy bleed into each other)

a loating point value. And is as a extra channel outside rgba.

C) the z buffer calculated in this manner is absolutely free from the renderers standpoint the data is just wirtten out to the file. Causes your pipe allmost no overhead whatsoever!

Use real z buffer its more accurate, read the sdk on how the data is stored in iff. Also read composition tuts they tell you how to circumvent the un antialiazed quantity of the z.

You can however easily make a shader That outputs the dpeth in RGBA foormat or any channel thereoff. its pertty simple. But it would be good if you knew the clippingplanes distance beforehand! To do this: just connect point camera Z to a set range node (adjust the set range to reflect how far you clipping planbe remevber forward is negative z so reflect this in you node, bevare the z depth is fickle, even inside comp softs that understand it!) is and connect the output to any channel of a surface shader. Then assign this to your texture. You are now forced to make one extra pass for this z data. Now while you render this extra pass you can feed any other info on the 3 remaining channels.

you can use the zdepth shader on this site as basis for this override shader!

[amitc]

Thanks for providing more insight joojaa,
I am going to dig into sdk,

Is there a method to write the z buffer of rendered images into a text file? All I want in floaing point values for each pixel.

[joojaa]

Well you could make a custom output format!

[amitc]

No pun intended.
It would be useful if you can point me to some examples.

[amitc]

Ok I found something useful
This guy "Luke Tokheim" has written a iff2tga converter
and is opensource as well.
Very good documentation of iff format. Here is the link
http://www.stdout.org/~luke/iff2tga/
I think this link might be posted on the maya tools and maya api section as well (will leave this job for admins if they think this is useful)

[sentry65]

I thought a "true" Z depth image was not supposed to be antialiased because antialiasing is really just averaging of pixels and a pixel is supposed to be in a fixed depth, not averaged with another pixel elsewhere in space.

So if you have an object against a blank background, it'd get averaged with pure black and that pixel now rests on a depth plane further back in space instead of next to the rest of the pixels it's supposed to be next to.

It's the RGB and alpha channel's job to antialias

of course if you want an antialiased depth matte, you can always use the depth shader and render out a sequence with that and use that to do whatever effects you want. It's more reliable than Maya's Z depth channel in regards to using it for depth of field or color corrections because it doesn't rely on camera clipping planes that are constantly being adjusted by maya (if auto clip plane is checked on for your camera)

You can use Fcheck to convert files. But it'll lose the Z channel.