I’m trying to create a “fake” shadow for my object because I don’t like the natural shadow it makes from the lighting in my scene. I would like to create one light source that casts the shadow for my object, but I don’t want it to actually shine any light because I have other lighting in the scene for that. Is there any way to do this?
can you show a picture of this so i have a better understanding on what you want to change?
Render your scene with the real lights…
Render your scene again with only the fake light, but turn on passes - what you want is the shadow pass.
Compose (multiply) the shadow pass over the first rendered image.
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Hello, thanks for the response! I’m really new to blender so I’m not sure how to compose the shadow pass over the rendered image. Could you explain how that’s done? If it’s a complicated topic, could you point me to a tutorial on the topic?
You don’t have to do it in Blender if you just want to render an image, you could just use Photoshop or Gimp.
Just add the shadow layer on top and switch the blending mode to multiply. That’s it.
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Read up on using “render nodes.” The node that outputs a render-layer can output a number of things … including, “shadows.” So, you can take “just that particular output” and use it. For instance, you might use it as as an input to another node so that it selectively darkens the particular area where the shadow falls. (And/or “does anything else you come up with” in that same area.)
Really, “nodes” are where all the real magic comes from: the ability to isolate particular outputs from a render (and other sources) and to manipulate them any way you can dream up to achieve the effect that you want. It is “the ultimate digital darkroom.”
Speaking of darkrooms, in the old-school days that I still enjoy dabbling with, we’d speak of “burning in” and “dodging” to refer to a similar manipulative technique: using pieces of cardboard and other tools to selectively alter the amount of light, hence the exposure, darkness, contrast etc of various parts of a print. Many folks just don’t realize how fundamental those techniques were to the “natural-looking” photographs that they remember from books. There really is no such thing as *“photo-*realistic.” 
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