Can a 45-bit PNG be output from Vray with a gamme of 1.0?

[davision]

I wanted to get a 48 bit PNG (not 45-bit as i typed in subject) output from the VFB at Gamma 1.0. Is that possible? It seems to always be at 2.2 no matter what I do.

Do I have to use EXR to get it out at gamma 1.0?

[dans]

The Override Gamma option in the save image dialog seems to work and does save the PNG file differently (I saved the current channel from the V-ray Framebuffer, 3ds max 2017 - V-ray 3.40.05).

When you view a saved PNG in 3ds max (Rendering > View Image file) 3ds max knows from the data stored in the file that it was saved at gamma 1.0 and will gamma correct it when displaying it. So it will look the same as a PNG saved at gamma 2.2.
If you open it in Photoshop or some other image viewer then it will look different as you expect.

Daniel

[davision]

I was using RPManager -- it doesn't let me adjust gamma for some reason. But thanks for the explanation.

[dans]

Well, then you should be able to use MAXScript to set the file output gamma to 1.0 (can be set in the 3ds max preferences dialog in older 3ds max releases; Note: this is not the same as the display gamma option which is still there). This will affect all low dynamic range outputs (JPG, PNG... but not EXR). Simply enter this code in the MAXScript Listener box and hit Enter.

fileOutGamma = 1.0

Since this is also a system setting, you will want to set this back to the default 2.2 after you saved your file.

fileOutGamma = 2.2

Use this code if you want to know the current value:

fileOutGamma

It can also be set via Backburner Monitor in the Job Details tab if this helps.

Best Regards,
Daniel

[davision]

Thank you very much for the tip Dans! Do you know if this variable is persistent? Or does it reset if you change the output file name. Basically what I'm asking is: if I switch passes in RPManager -- which basically reconfigures all the render settings, will this gamma value be remembered or reset?

[dans]

This setting is completely independent of filename and renderer. I'm not sure what switching passes in RPManager involves - so I can't comment on that. If it isn't a setting RPManager overrides specifically then whatever is set in the 3ds max file will most likely still be used.

The proof of the pudding is in the eating. Do a simple teapot scene and set the file output gamma value to 5.0 and the result should be pretty obvious

Daniel

[davision]

Point taken.