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I blend my character (to the right) into the scene. I want some shadow casted by the character over the doll (real-life). How do I do it in CYCLES? enter image description here

thododo
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  • You will need to recreate the doll in 3D just to cast the shadow and use the same technic explained by @parameciostudio – YoMismo Oct 01 '15 at 08:41
  • I did that in https://www.youtube.com/watch?v=HZQKn0THf8s go the the tornado scene and check the shadow. It isn't a good example since the quality is bad (it's a hobby for me) but the technic is the one posted in the answer adding a cilinder for the straw roll. If the answer is not expanded I will post my straw roll and the technic when I get home. – YoMismo Oct 01 '15 at 08:48
  • Sorry but what's the technique you mentioned? – thododo Oct 01 '15 at 09:35
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    Not me, @parameciostudio. You need to set that object to only receive shadows and not render any material on it, I don't remember where you select that (check object properties), have to get home to open my old blend files. If no one can answer before I will tell you how it is done when I get home. – YoMismo Oct 01 '15 at 09:40
  • Check this http://blender.stackexchange.com/questions/6796/how-to-render-a-shadow-without-the-object-in-the-scene – YoMismo Oct 01 '15 at 09:46
  • Oldie but goodie http://blender.stackexchange.com/questions/518/how-to-make-a-model-cast-shadows-onto-the-world-texture-background/519#519 – iKlsR Oct 02 '15 at 16:20
  • @YoMismo It works casting shadows, but how can an object receive shadows without casting (the real object already casts the own shadow)? It is quite easy with Blender Internal, but I didn't find a quick solution with Cycles yet. – parameciostudio Oct 02 '15 at 18:12
  • Have you tried @parameciostudio answer? Looks like that is the way, you can also check the next blenderartist thread http://blenderartists.org/forum/showthread.php?251177-Cycles-how-to-get-a-plane-to-recieve-shadow-while-invisible&highlight=cycles+shadow+catcher I haven't done it with cycles – YoMismo Oct 02 '15 at 21:58

2 Answers2

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As for the floor, you should add a transparent object receiving shadows.

Since Cycles has been thought for photo-realistic renders, there's no easy way to isolate shadows.

You can use Layer and Render Passes.

Foreground

This layer contains all you want to render (your character)

enter image description here

Transparent objects receiveing shadows

This layer contains the helper objects that will receive shadows (the puppet).

Since we won't use any color informations, we'll use the Diffuse Direct Pass.

enter image description here

Background

This layer contains the shadow of our hero.

To avoid the "helper object" to cast any shadow, we'll exclude its layer.

enter image description here

Background image

enter image description here

Scene

enter image description here

Composite

enter image description here

Use the RGB Curve Nodes to adjust the shadows and to set the white level (white is transparent in Multiply Node)

parameciostudio
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    I think it would be helpful to add details as to how they might do this. – Ray Mairlot Oct 01 '15 at 08:14
  • So... what about the doll? And it'll be nice if you show me a more detailed answer. – thododo Oct 01 '15 at 09:31
  • just tried to give the floor a Transparent shader but It didnt help – thododo Oct 01 '15 at 09:36
  • Hey @RayMairlot, If you are the same Ray Mairlot that has youtube tutorials on Blender I would like to thank you for that. They are great and the main title of the video (see comments to the question) have been done using your technique. I also thank you in the credits (hope you don't mind). – YoMismo Oct 01 '15 at 19:04
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Ok since the other answer hasn't been expanded, here goes my explanation.

I did this with Blender Render, but in the link I posted as a comment to your question goes the explanation for cycles. Regarding the doll receiving the shadow of your character...

As you can see in the next image, I have setup a ground and a straw roll that matches the background (sorry, I lost the background image but I used it as reference to place both ground and straw roll).

Image setup & material

As you can see, for the straw object a material is created, in the material you can see what I have selected in the shadow section (receive, receive transparent and shadows only). The rest of the material sections/options should be unchecked.

The next image shows a render, as you can see neither the ground nor the straw roll can be seen, just the shadows the tornado creates.

Render with only shadows

And the final composite

Final composite

YoMismo
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