AO Shadowcatcher


Anyone know if there is a Matte / shadow material ( like max ) that will catch shadows or more importantly Ambient Occlusion.

I have ShadowCatcher.cob plugin - but this doesn’t seem to do it



multipass and render a AO pass


Doesn’t that mean I have to have a floor to AO - which will come out in the colour pass?

I want a transparent floor with the AO reacting as tho there is a floor there and the resulting image - I don’t want the floor in the render at all - just objects

Don’t mind doing multipass - but don’t think that will work?


Create a material with a filter shader in the alpha channel. Load the AO shader into the filter, check the “enable clipping” box and set low to 100% and high to 0%. There’s your AO catcher!


Adam, that is very sexy. Nice.


Isn´t it easier to invert the gradient? :wink:


That too. :stuck_out_tongue:


Great thanks. Perfect. Kudos.

Have made and attached the material in case anyone wants it.

The low to 100% and high to 0% setting is faster then moving the gradient diamonds - unless there is an actual inverse switch for it… couldn’t see one.



right-clic on the gradient -> invert nodes


neat trick Adam! Thanks
This can be used for other things too…
-in reflection channel for floor reflections that fade off.
-in luminosity channel for Tron-like edge glows
-in luminosity and in bump/displacement with some added noise to make the sea’s foam that touches the sides of a boat


Are you able to post an example? i’m not getting anything close to what you saying with the mentioned method?


Fede, I gave it a go… seems to work well.
I know this look could be achieved in lots of other ways, but the nice thing here is that you just add objects and the rest is automatic.


Hey lewisrowe, you are 100% correct and thanks for the scene. My set up was not correct, that is why it wasn’t working correctly. Now I know though, so thanks.


Well, it took me a while to figure… the trick was to ramp-up the luminance colour brightness really high then let the multiplied AO act like a masks that the brightness shines through. Thats what gave the grads the nice white-to-cyan-to-dark blue look.

Now AdamT’s got me thinking, I might try the boat in sea idea next…


Just beautiful lewisrowe. Having fun dissecting this shader.


I’ve just tried AO in the bump and Displacement channels - they dont work there. pity. would have been good for liquid surfaces.


When i was developing my boat system last year i spent a huge amount of time tinkering with this kind of idea, that really should work.

Great tron concept Lewisrowe, and thanks for sharing.


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