Hi Guys,
I am houdini noob, and hope you can help me with an issue which is baffling me!

I am attempting to render the z depth of a cloud and am encountering some strange issues with the output of the z-depth channel.

I have adjusted the frustrum of the camera to fit the cloud objects z dimensions and created a extra image plane in Mantra for “Pz”. The colour channel renders fine, but the Pz channel (as you can see in the image) isnt rendering properly. It seems to be rendering voxel data around the cloud. However, I don't get this issue if I render it with ‘Stochastic Transparency’, but no matter how high I increase the samples I can't get rid of the noise in ‘Stochastic Transparency’, hence why I opted for the normal transparency render.

Can anyone shed some light on this issue please? I would really appreciate it!

Thanks in advance

This is why deep camera maps were developed as I assume you want to composite the volume over other objects.

If you are using Nuke, you can generate these deep camera maps for the volumes as exr images and bring them in to nuke as deep maps and composite your volume that way.

The deep camera maps can get quite large though.

Hope that helps.

Yes , the best way for Volumetrics such as PyroFX and Cloud is using Deep Compisiting .
In this method you can have your 3D Object in the Nuke (like Point Cloud) and so you can generate Z depth in the Nuke easily .

About your problem if you don't wanna use Deep Compositing , you can use a simple trick for solving that.

You should know that when you use "Stochastic Transparency“, to take best quality without any noise in the other passes such as Z depth or Position pass ,you have to set ”Sample Filter“ parameter in the Mantra for these passes to ”Full Opacity Filtering“.
But in this case you take same result with turing off ”Stochastic Transparency" . Now to solve this problem you can simply multiply Opacity(Alpha) channel with Z channel in any compositing software like Nuke !
I made a simple project about this method for you , Of course I used Nuke for compositing and I upload this Nuke project for you too :wink:

Thanks a lot for the help guys! Your information was extremely helpful.

Using the .rat method, i did manage to get the data out. I don't use Nuke, so extracted it via AE instead. The RGB/Alpha and Pz did not require a composite because I'm using the Pz data for realtime raymarching of the cloud in-game.

Your help has been really valuable. Thanks

PaulC
Thanks a lot for the help guys! Your information was extremely helpful.

Using the .rat method, i did manage to get the data out. I don't use Nuke, so extracted it via AE instead. The RGB/Alpha and Pz did not require a composite because I'm using the Pz data for realtime raymarching of the cloud in-game.

Your help has been really valuable. Thanks

I don't work with AE , Can you open rat files in the AE ?

Because I have to use exr format for deep compositing in the Nuke :?