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Basically, I just want a shader for my ground plane that receives shadows but is otherwise pure white. I figured this would just be a simple checkbox or two but it's proving to be more complicated. Most of the answers I see out there involve doing lots of complicated node editor stuff but those questions are 2-3 years old so hopefully there's a better way now?

I'm using Cycles.

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There is multiple way,but I see you dont want complex node trees so I will tell you the easiest one.

Add a plane and make the following material:

<Material

It basically say that the plane the actual material is diffuse but the camera see it as a white color. Now we have a pure white color.

Render tour image with :

  • Shadow pass.
  • AO pass.
  • Object index pass.

Now we come to the post production,we multiply your shadows and AO to the image but we have to make sure we are applying only on the plane.

So we do as follow:

While The mask is the object.

Post

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    $\begingroup$ I ended up following this answer from a duplicate question and got it to work: blender.stackexchange.com/a/3003/19882 , but it uses multiple RenderLayers and I didn't really understand it but thankfully it was well explained enough to duplicate; although I think I get it now. But I still want to try your way, too. Will it render faster? With the way I have it now it renders 3 times and then composites which tripled my render time. $\endgroup$
    – Kenmore
    Mar 24, 2016 at 22:51
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    $\begingroup$ I think my way is the fastest and the best one,but the one you followed is solving a problem that my way have,the problem is that the shadow pass wont include the shadows from non-lamps like plane lights. But most of the time I only use AO for product visualization so I use my way. $\endgroup$
    – Omar Emara
    Mar 25, 2016 at 14:41
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    $\begingroup$ This solution includes AO, but no shadow, right? $\endgroup$
    – Martin R.
    May 18, 2017 at 13:23
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    $\begingroup$ It may include shadows from lamps if you used the shadow pass as well. $\endgroup$
    – Omar Emara
    Jun 2, 2017 at 12:17
  • $\begingroup$ What if I wanted to have screen space reflections ? $\endgroup$ Feb 2, 2022 at 18:15
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Light it up (enough)

Simplest solution (but not suitable for all task) would be to set up lamps in order ensure enough light for the non-in-shadow pixel and using a full white plane (e.g. with a Diffuse shader with RGB Color = [1;1;1] ).

enter image description here

In the pic of the studio above, for example you can see that the light source has a Strenght of 5: the value, combined with the lamp rotation (wich is related to the density of the rays hitting the surface) is able to give enough light to reveal the full color of the plane.

Pro's:

  • Natural looking: has the is like setting up a studio in the real world (Cycles is good at doing this, it's a physically based render engine), so your scene will often looks less fake compared to the soloutions that involves Compositing or Light Path-shader-switching.
  • Easy to understand

Con's:

  • You can't have full control on the scene lighting, especially if you are looking for non physically based effects. And you'll probably struggle a bit to find a compromise between the how to light up both the model and the plane the way you like them.
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I have a very simple solution without any special nodes that works for me.

Cycles > Film > Transparent

Plane beneath your view: Object properties > Visibility > Shadow Catcher on

Now you have a tranparent background with shadows. With many stock apps you can make the transparent background pure white.

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