Current shaders draw the solid (clipped) pass, and then follow with a fade pass.
This change is to stretch the alpha for the fade portion, to provide smoother visuals, so the fade portion would start fading from where it was clipped, instead of 1/2.
In addition, the ztest was change for the double side shader pass, so you don't get the darker layer banding in some cases.
Current shaders draw the solid (clipped) pass, and then follow with a fade pass. This change is to stretch the alpha for the fade portion, to provide smoother visuals, so the fade portion would start fading from where it was clipped, instead of 1/2. In addition, the ztest was change for the double side shader pass, so you don't get the darker layer banding in some cases.