On Saturday, July 14, 2012, John Hunter wrote:

On Sat, Jul 14, 2012 at 11:48 AM, John Hunter <jdh2358@gmail.com> wrote:
I do not understand why in the following example, if I set patch_alpha=1.0, I do not see the shadow effect.  I would expect to see it for the the rightmost four bars, where the original bars do not entirely occlude the shadow, so even if alpha is 1.0, there are parts of the shadow that are not behind the original bars and should still be visible.

I now see that this line explains the behavior



so maybe I should amend my question: is this desirable that the shadow alpha is 1-patch_alpha, since an alpha of 1 on the patch does not imply that there is no visible shadow? 

I would argue that the shadow's alpha should equal the patch's alpha.  The more opaque the patch, the less light that should get through.  Could there have been an alpha blending reason for this?

Ben Root