I THINK I GOT IT! (I'm sure by now nobody cares anymore...?!)
And it's in one formula that may still be optimized:
S = source
Sa = source alpha
D = destination
Da = destination alpha
((D+(S-D)*Sa)*Da+S*(Sa*(1.0-Da))/(Da+Sa*(1.0-Da))
There you go... just in case you've been through the same pains...
Let me know if you find this to be wrong
And it's in one formula that may still be optimized:
S = source
Sa = source alpha
D = destination
Da = destination alpha
((D+(S-D)*Sa)*Da+S*(Sa*(1.0-Da))/(Da+Sa*(1.0-Da))
There you go... just in case you've been through the same pains...
Let me know if you find this to be wrong