Right now i know the following:

**Bullet speed:**150 pixels/sec

**Travel distance:**100 pixels

**Current opacity:**100%

**Delta time (dt)**

As i understand it, i need to calculate the speed the bullet takes to travel over the set distance which should be

**time = distance/speed**.

*So 100/150 = 0.66 pixels/sec right?*

But this is only how far it moves each second, so to calculate the distance each tick (to get frame based animation) you probably have to do

**0.66 * dt**?

*This gives me approx 0.0106 pixels/tick...*

This is where it gets confusing and I'm sure that i've approached the whole thing wrong up until now... but how do i know how much the opacity should decrease each tick?