"Billboard" Transparency with Masked Shadows?

My experiments with using planes and images textures with alpha channels, (.png), have yielded results that show the background color through the plane, but cast a rectangular shadow from the plane, itself, rather than from the “masked” image, (think of trees, here).

Can anyone share the exact material settings to obtain perfect billboard transparency and shadow casting?

And, if anyone could share the method for keeping all billboards aligned, facing the camera view, this would also be much appreciated.


Greg Smith

Here’s a quick .blend:


Trashad button in Shaders on the material Receiving the shadow, Area lights for shadows.

To have them follow the camera put a TrackTo constraint on each with the camera as the target, but that could be tricky if it’s trees and your camera goes overhead!

The best way is to have intersecting planes in the shape of a cross from above, or even 3 intersecting planes, so from above it looks like this: *



It seems I had most of the settings right, but it looks like the key to success is in the “Calc Alpha”, (I used “Use Alpha”), and in the “Z Trans” buttons being pushed. The file works with a spotlight, as well.

It will be nice when the material editor gets its overhaul. I hope some of this process will be simplified.


Greg Smith