Fade out object with many materials without use of material transparency

Hello there.
I know this has been discussed here several times but I still cannot find clear answer:
Is it possible to fade in/out the whole complex object with many materials used?
All advices here lead to some material shader solutions and that is not handy, fade out would have to be done for all materials used. Imagine joined model of a human with 30 materials - it should smoothly dissapear from the scene. Sure I can do two renders (with and without human) and fade it in post… but i would love so much if there was some “proper” solution since this need happens often in my work.
Thx a lot.

Good morning, @ondrej.sevcik! I’m not sure which exact material solutions have been suggested, but the method described in the below video seems to be the best way I’ve been able to find to do what you are asking. Understandably, you are between rendering twice with and without your object and adding an attribute node to each material to control alpha at the object level. I’m not sure if you are using Cycles or Eevee, but if you are using Cycles and you don’t want issues with your back faces showing through as your object fades, you’ll want to roll your own backface culling shader like this:

Here’s the video explaining the custom object attribute used for object-level alpha control:

Let us know if you still need assistance and have a great day!

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Hello and thanks for your reply. I am using evee since cycles are painfully slow. Anyway what I understand is that the only way to fade out object with many materials is to fade out every material - one by one, right?

Well, I assume you are keyframing your fade, so ideally you want to be able to keyframe one property and control the entire object. The method in the video creates a custom attribute at the object level that allows you to keyframe just one slider to control the alpha for the entire object. You just have to do the initial legwork of connecting the attribute node to the alpha socket for each material you want to fade.

Then, in the Object properties, you keyframe your custom alpha attribute for the entire object et voilà!

If you are using Eevee, you don’t have to worry about the backface culling shader I demoed above - just the Backface culling checkbox under the Material Settings (also shown in the video).

I might be able to record a short video of the full technique if you think it would be helpful. Let me know.

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