View Full Version : Shadow catcher & alpha reflection

08-16-2016, 03:12 AM
There is probably a simple solution for this, but can't find it.

Basically I have object standing over ground plane. Ground material has Shadow Catcher -node with reflections enabled.

Rendered image displays object with reflections and shadows but If I save rendered image as 32 bit PNG file, saved image has alpha, with shadows but reflections are missing. If I save image as 24bit PNG, reflections are there with shadows but alpha is missing.

How I can get image with alpha in reflections and shadows? I have tried playing Compositing Buffer Export filter without much success.

LW 11.6.3

08-16-2016, 04:01 AM
See my tutorial how to extract Shadow Catcher data
You will need TrueArt's Node Library to do that

Then you can do whatever you like with data.

08-16-2016, 04:27 AM
Apparently I am doing something wrong :( Reflection sill missing from save 32bit file.


08-16-2016, 04:39 AM
You need shadow data in post-processing stage, right?

So Shadow Catcher node, plug to Split Material,
and take its Transparency output (IIRC), only this one,
and plug it to Diffuse Shading,
or to Diffuse Shading in Make Material,
and output from Make Material, to Material input in Surface.
This way you have one pass, just with shadows.
And unplug it.
And you have RGB.
Then in post-processing merge these two passes the way you want.

What you did above is splitting everything, and joining everything. 1-1+1 is still 1, isn't?

08-16-2016, 05:31 AM
Yup, need reflections for post.

Here is every outcome when connecting from split material to diffuse shading. Still no reflection with alpha.

08-16-2016, 06:48 AM
What is it that you want do do with your reflection? As far as I know reflections will never show up as part of an alpha channel. I have used rendered reflections in Photoshop or Aftereffects by multiplying them over a background image. No alpha needed for that.