Vray, 3ds max, PNGs, Photoshop & Alphas

[DestinHalfmann]

Hi guys,

This has probably been asked before but I could not find the right information.
Is there a way to save out a PNG with alpha/transparency in Vray from max without having to defringe/remove matte in post?
There was a time when we could choose pre/un-multiplied alpha when saving top PNG from max, but that is not the cass anymore.

Since we've to a more automated/streamlined workflow in Vray 5, this seems to be the last frontier before we can deliver PNGs for clients without Photoshop involved in the process.
Ofc. rendering to EXR/TGAs gets rid of the fringe issue, but it would still involve having to save to PNG in post.

I also noticed that the PNGs provided with the Chaos Scanned materials to not have edge issues. Have these been through PS to have matte removed and/or defringed?

[fixeighted]

You shouldn't have any issues if you're environment colour is black.
Or maybe I misunderstood the problem...

[DestinHalfmann]

You shouldn't have any issues if you're environment colour is black.
Or maybe I misunderstood the problem...

Nope not at all.
My PNGs always have a thin black alpha/edge where as my exr do not.

Examples - PNG from max to PS on left - EXR from max to PS on right

[fixeighted]

You're correct of course.

[hermit.crab]

That's caused by the fresnel specular, which is white along the edges. If you have a black background, the png's color depth limitation would interpolate the black and white into this grey edge. To bypass it, match the background colors of both platforms.

[seandunderdale]

Would a 16bit png solve this?

[hermit.crab]

I did further testing and this seems to be caused by the method with which PS applies (or reads) .png transparency; the same image doesn't have dark edges present in Nuke. I couldn't find any .png specific settings in PS and adding a Layer Mask from Transparency produces identical results. I guess manually removing the edge is also a solution...

[seandunderdale]

There is a free plugin called superPNG for Photoshop which has some alpha options. Might be worth testing with that too.

[fixeighted]

SuperPNG does nothing to solve this I'm afraid. Looks like it's not possible to achieve purely in the saving process.
This post did however help me solve the fringing and the incorrect shadow density problem with pngs...in AE simply applying Set Matte fixes both issues.
Saving that png from AE, the transparency (therefore shadow density) is saved correctly when then opened in PS, so doesn't this point to Max's png saving process doing something wrong?

[hermit.crab]

Saving that png from AE, the transparency (therefore shadow density) is saved correctly when then opened in PS, so doesn't this point to Max's png saving process doing something wrong?

Maya has .png compression control, which when set to no compression resolves the issue greatly (in all .png cases the edge is still there, though less visible, whereas completely missing with .exrs). Unfortunately, 3ds Max does not have such options. I presume Nuke applies a "Set Matte" automatically, hence why the issue is not present there.

[fixeighted]

Aah, thanks, that is interesting...and also a bit weird LOL. You'd have thought that something as simple as saving an image would have the basic amount of control that the png format supports, regardless of software used.
Given that AD owns both Maya and Max I can't imagine why the issue is only with Max. Oh well