@yaorenliu If you will permit me to do so, I will make a suggestion about shooting photos so that raindrops will show up. If you want to capture raindrops so that they show up in your photos, you need to make sure that they are lit from the back. Try photographing the rain with a streetlight behind the rain drops, or any other light source lighting them from behind. In this photo, the raindrops are being lit from behind by the light coming from the light source at the top center of the photo.
@mbrutus Thank you. You are right, but again I have an excuse. The rain started when I was already in bed and I took the photo from my bedroom's window. No way I could change the direction! :-)