I am following a tutorial (2.62) which uses a material (?) setting, “Shadow(s) Only”. I can’t find such a setting in 2.70a.
Thanks for any clues.
Is this what you’re looking for :
Be sure to be in Blender Render mode, i don’t think there’s such panel in Cycles Render
edit : looks like Richard Marklew was faster 
Thank you, gentlemen. But I am using Cycles and this is for a floor to catch shadows in a camera motion study I’m doing to try to learn that art.
I didn’t realize it when I asked my question, but it appears the shadows only feature is automatic when I define floor tracking points - a “ground” is automatically added to the scene and, when rendered, it is invisible except for the shadows landing on it. Here’s my JPG note so I don’t forget this. There wouldn’t actually be a shadow there, but the feature works.
Attachments
That last step to put the images together, is it just done in the compositor, dropping out the floor where it’s white? Is there some way to get that shadow to be ‘cycles’ soft?
The floor appears to render as invisible except for the shadow. It is automatically created that way when the 3 tracker points are assigned to “floor”. It is a simple plane which can be hidden (H), but still shows shadows. The blurriness of the shadow is a function of the “size” setting for the sun (as is normal). I originally had it at 0, but here it is at 0.3.
There was no work in the compositor or in nodes. This is all done in the Movie Clip Editor with a 3D window open next to it.
EDIT: Although the “ground” is invisible, it’s white color reflects back onto the sphere as shows in this JPG. I found I could improve the realism by changing the “ground” to a gray color to match the porch floor in the video.
Here’s the final video: https://www.youtube.com/watch?v=MeM9UcT97VA&feature=youtu.be
