[brodie_geers]

Running through the blending modes in CS4, there doesn't seem to be a perfect mode to match your diffuse and reflection passes to a normal rendered output. "Lighter Color" is quite close but not exact. My tests were all with the reflection layer on top at 100% opacity.

Is there a perfect method to achieve an identical result posting these two images together?

Also, what should/could you use the roughness, fresnel, and motion vectors for? Are they just meant for reference or is there actually a way to use them in post production?

-Brodie

[dariolanza]

Hello Brodie,

The PhotoShop blending mode that is most similar to the way light behaves, is Screen.

In fact, you should put both the Diffuse pass and Reflections pass in Screen mode, over a pure black layer (absence of light), and adjust each pass contribution with the layer opacity slider.

You can see an example of a simple setup in this image:



Although the Screen mode doesn't behave 100% exactly as the physical transport of light does, it offers the most similar result within the PhotoShop native blending modes.
You can match the original result with a little brightness tweaking.

Let me know if this answers your question.

Dario Lanza

[RichG]

For the absolute best result, you need to look into linear workflow. First of all, export your images in a 32bit format like exr, then use Linear Dodge (Add) mode in Photoshop. Linear Dodge was always the ugly version of Screen, but Screen is actually an inaccurate compromise designed for the days when we couldn't access brighter than white data. Given Maxwell's abilities in this area, it's worth us all changing our workflow. Unfortunately Photoshop's 32bit workflow is still a bit lacking, even compared to it's sister product After Effects but it's worth the effort.

There's an excellent podcast at FXGuide.com where they explain why we've all been doing it completely wrong using screen.

http://www.fxguide.com/modules.php?name ... rlight.mp3

Not to disrespect the previous contributor (I bow down to the NL team!), it's the way we've all done it for years but honestly, the benefits of getting your head around linear workflow are huge and far outweigh the pain of the learning phase (which I admit I'm still struggling with at times).

[dariolanza]

Yes, completely agree.

The more accurate result is achieved using 32Bits images and Linear Dodge blending mode.

But unfortunately, it is not already the most often workflow for most users, which still work over 8Bits images.

Knowing this, I was describing the traditional compositing method, most often used with 8Bits and Screen mode.

But completely agree with the 32Bits and Lineal Dodge workflow due its superior accuracy.

Regards

[brodie_geers]

Great, I'll give the 32-bit/linear dodge workflow a shot. Thanks for the info!

-Brodie