Hello! I'm working on a space game. I need with help with rotating the rocket sprite so that it points parallel to the planet, but points backwards from the rocket's ‘Parallel velocity’ relative to the planet. I'm trying to use this to simulate atmospheric drag by applying drag in the opposite direction of the parallel velocity so you slow down, but I don't know how to do what I said (probably because it barely makes sense). Hopefully this image helps to explain what I mean.

- White arrows: ‘Parallel velocity’ (What I need to find now)
- Green arrows: Drag direction (found by @deck26)



Thank you for reading!
Game shared from my alt

If the planet is properly centred you should just need to point towards the centre and then turn 90 degrees (clockwise or anti clockwise will depend on the direction of rotation but you could perhaps have a variable for that).

deck26 wrote:

If the planet is properly centred you should just need to point towards the centre and then turn 90 degrees (clockwise or anti clockwise will depend on the direction of rotation but you could perhaps have a variable for that).

Thank you! But, now I just realized I need to know the parallel velocity to get the proper drag direction.

bump

Seems like you just need to do have -sin(drag dir) and -cos(drag dir) as x and y velocities.

ExtraMental wrote:

Seems like you just need to do have -sin(drag dir) and -cos(drag dir) as x and y velocities.

Got it. I was trying to find the parallel velocity though, so I could apply drag in the opposite direction of the parallel velocity. I should have stated that in the post, sorry. I keep forgetting to put things inside the original post.

I was able to find an equation that works. Thank you guys for giving me ideas though!