So I am making something for a video overlay. It should be semi-transparent to allow some of the video to be seen through it.
This was not a problem at first. The item was a glass ellipsoid with text (opaque) and other objects (opaque) in front of it which casts shadows and reflections. Using glossy surface and playing with roughness and also adding a transparent shader (mixed shader) did the trick.
Now the project includes putting something opaque behind the glass which should be diffracted through it.
Transparent shader does not diffract what is behind it. The glass shader does but once it is introduced, I lose all transparency in the glass.
Adding a mixed-shader with transparency gives a diffracted and non-diffracted view of behind. Adding a mixed-shader with holdout makes the ellipsoid and its diffractions semi-transparent, even so the opaque object is now semi-transparent (though the glass). Also tried refraction shader. Same issue as glass.
What I am trying to do is make anywhere where no light hits the glass (environment transmissions/reflections, refractions) are all transparent but opaque objects in front and behind the glass are still opaque.
Blender 2.73a, Cycles. Nodes.