Does anyone know if it is possible to render just an object’s shadow on a plane without rendering the object itself? I’m using Yafray with full GI if it makes a difference.
You can try setting the objects alpha to 0.001 and not turning on TranspShadow on the plane, however this doesn’t seem to work in yafray, alpha 0 objects don’t seem to be completely transparant. Also it gets in the way if you want the plane to have TranspShadow for something else.
Another option is based on a trick for giving particle systems shadows:
- Set the lamp as the camera (select, ctrl+NUM0)
- hide everything except the object
- download the alphamatte sequence plugin
- render the object through that plugin and save the image
- Still with the lamp as the active camera, subdivide the plane a bit and click “Make” next to the word “Sticky” in editbuttons (F9)
- add the image as a texture onto the plane - set the image to “Clip” in the texture options.
- Choose “Sticky” in the “Map in” panel
- Set the texture to Subtract and use the col slider to set the shadow intensity.
However this is a bit tedius (particularly if you have many lamps, or you have an animation), and impossible if the lamps move during the animation (since the sticky coordinates would have to change). Also it is a bit inaccurate if the shadow reciever isn’t subdivided enough. Also it doesn’t seem to work in yafray either.
Ok, I’m out of ideas…