Need help with partially alpha rendering


I’m using a toon-shading style and trying to render only a shade section. But I don’t know how. I don’t want to render a white section (in pic 1) and I only want to render a purple section (pic2)

(this pic was made in photo editing program to explain what I want. Not from blender itself)

I’m also a newbie. I may not understand all technical term but I’ll try. Thank you.

Not sure what you are going for…ie: what your object is…is that a cylinder in Blender or is the the shadow from a filled circle?

But I believe it will end up ( have to use cycles) and then your best bet I think would be to use cryptomate and the compositor.

in 2.81 eevee supports holdout shader which should do exaclty what you want

wow. I never know that method before. Thank you. I’ll learn it.

That’s a very good answer. Thank you. I’ll learn how to use it.

You’ll have to use eevee and the shader to rgb node to do this. It converts the shading on the object into a texture that can be connected to the factor of a mix shader node and used to blend between two shaders (black in the texture for the shader in the first slot of the mix shader node, white for the shader in the second slot). You’ll then have to use the backfacing output of the geometry node and another mix shader to erase the backside of the object. Just make sure you set the blend mode on the shader to alpha blend so that the transparency will work:

Here’s the blend file: toon.blend (640.6 KB)

Edit: I just realized that you don’t need to add the second mix shader and geometry node if you just uncheck the “Show backface” option in the shader settings section.

WOW!. That’s absolutely amazing. This is exactly what I want. Thank you so much. I’ll study it.