Problems with comping Vray passes in Photoshop

[A.Mitov]

Hi guys.

I have some problems layering rendered passes in Photoshop. Everything works great and looks the same as the beauty pass when layering the 32-bit .HDRs. However, if I layer 16 bit .PNGs instead, the final result is not equal to the beauty pass. The render image before compositing is neither overexposured nor underexposured so I should have enough color information even in 16 bits.

 

Here's how I layer the passes in Photoshop:

(Linear dodge add) Specular

(Linear dodge add) Refraction

(Linear dodge add) Reflection

(Linear dodge add) GI

(Normal) Lighting

 

You can see image of the comping results:

[ATTACH=CONFIG]47448[/ATTACH]

 

Any clues?

[Brodie Geers]

I don't recall the reasons behind it but LD/add is only valid in 32 bit. For 16 and 8 bit you're better off using Screen. That should get you closer although it probably won't be a perfect match. I've never tried it but I wonder of opening your PNG's, converting to 32 bit mode, and using LD/add would work. Might be worth a shot.

 

-Brodie

[kristofferhelander]

16-bit PNGs are not floating point and not Linear so the maths breaks down. You can perhaps sort of save it with Screen as mentioned. But for true compositing you are better of using floatingpoint 32bit, OpenEXR.