Discussion of article "Studying the CCanvas Class. How to Draw Transparent Objects" - page 9

 
Реter Konow:

You could reason it this way:

The first glass reduces the intensity of the light passing through by 40 per cent. The second glass reduces the intensity by 50%, but since it only receives 60% of the original light, it will halve it by half. Then you get 30 per cent of the original intensity.

I agree.

Right.
It also sums the probabilities of the dependent events.
New_alpha=a1+a2-a1*a2
 
Excellent article. Thank you!