Problem with two shadow catcher planes


Here is a problem I could not find a solution for: I am trying to cast a shadow of a 3D object on the ground AND on the wall of a building. So I have created two perpendicular shadow catcher planes (white 3D planes with blend mode "Multiply"). That basically works fine but where the planes meet there is either a dark or a bright line - I cannot adjust them to join perfectly. Is there any way to solve that?

Thank you!



  • Triem23Triem23 Moderator

    Adjust your shadow catcher plane's anchor points to be along an edge (so, if your planes are 1000x1000, shift the anchor point by 500px). Place a point at the junction of floor and wall and parent both shadow catchers to it. Zero out the position properties of the shadow catchers, then rotate your planes into alignment? This should perfectly align those edges. 

    If you're not familiar with Anchor Points, 9:29 in this video discusses them

  • edited April 2017

    Thanks for the help. With the method I get the planes alinged perfectly. But still there is a little bright line where the planes meet. In the image it starts in the bottom right corner.

     Shadow problem

  • Triem23Triem23 Moderator

    This forum doesn't host images. You'll have to upload to a photo share site and paste the image link. Or, stick it in a cloud folder and share the link. The forum software isn't my favorite. 

    Ok, here's the workaround. Copy your lights. Select the light copies, and shadow catchers layers, then right-click and Make Composite Shot. In the Comp, change your shadow catchers back to normal blend. Maybe let them overlap by a pixel or two. 

    Open up the shadow catcher layer properties and make certain they cast and receive ambient occlusion. If you still get artifacts, go into the properties menu and increase shadow map size. 

    Once the shadow looks good (against the white) return to your main comp and set the embedded comp's blend to multiply. 

  • Thanks once more. The workaround seems to be a bit complex for a beginner like me but I'll give it a try a little later and report.

    I have stored the image in Dropbox. I can see it on my PC but it does not work from my iPad (reported a a broken link).

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