VRay ZDepth failed rendering detail.

[Erizo]

Hi,
I know there are some discussions about rendering a correct ZDepth with VRay.
But there hasn`t been an satisfying solution. So I´m starting a new post.
In my opinion the ZDepth layer mustn´t be antialised. But using filtering off the renderer ignores small geomertical details which leads to flickering animation.
See the attached image to compare VRayZDepth and MRayZDepth.
Using post DOF works fine with the MRay-Version of the ZDepth-layer.
I´m using VRayProxys so it´s not possible to render the ZDepth with another renderer then VRay.
Any hints, tips or solutions welcome!

[instinct]

The Problem is not AA but the way VRay decides which fragment is used for the ZDepth. By default VRay uses the fragment with the BIGGEST weight (=the one with the most influence on the final pixel).
In the case of small detail it might be that the subpixel weight may be lower then the Background it is in front of and would hence get dropped.

At least i think this is what is happening without seeing the RGBA

There is no preference in the GUI tho. It can be overridden if you develop a custom renderelement (or any plugin that has access to the VR::SequenceData structure) and set the member params.gbuffer.unfilteredFragmentMethod to 1. Then the frontmost wins even if its weight is relatively low.

Regards,
Thorsten

[Erizo]

Hi Thorsten,
thanks for your answer. That makes sense. Unfortunatly I´m not able to do such scripting.
But I just found another option. When writing an *.exr you are able to save the render elements to that file. Which, in case of the ZDepth is the same problem. But using the G-Buffer instead of the render elements it´s posible to use the `normal` ZDepth and not the VRayZDepth, which is exactly what i want
Sadly there is a new problem popping up. Using the G-Buffer you are not able to define a range for the black- and white point like you can do using the render elements. The result is a dynamic change in the ZDepth when rendering a sequence where Object are moving or showing up in the background. Seems that the renderer checks and updates the range for every single frame in animation
Any clues for this problem?
Thanks

[vlado]

Seems that the renderer checks and updates the range for every single frame in animation
Any clues for this problem?
Thanks

This is a 3ds Max thing; do camera clipping planes have any effect on this if you enable them?

Best regards,
Vlado

[Erizo]

Hi Vlado,
yes clipping planes do have an effect. But only if you clip geometry. If you try to expand the range way behind the farest geometry in the frame it has no effect. It seems that range depands on the visible geometry in a rendered frame.
This dynamic ZDepth range makes it nearly impossible to do proper post Dof
Is anybody able to write a script which makes you define fixed ranges for the G-buffer ZDepth channel in .exr?
Would pay for this

[vlado]

We could simply add the option that Thorsten mentioned; it would be a lot quicker.

Best regards,
Vlado

[Erizo]

I´m really interessted in this solution.
So how could we get together?
Is it a script which has to be written, or is it necessary to develop a kind of patch?
Feel free to private message me.
Thanks in advance

[vlado]

You can email me to vlado@chaosgroup.com for more info.

Best regards,
Vlado