python - Finding vectors with two points

Monday, July 29, 2019

We're are trying to get the direction of a projectile but we can't find out how

For example:

[1,1] will go SE

[1,-1] will go NE

[-1,-1] will go NW

and [-1,1] will go SW

we need an equation of some sort that will take the player pos and the mouse pos and find which direction the projectile needs to go.

Here is where we are plugging in the vectors:

def update(self):


    self.rect.x += self.vector[0]
    self.rect.y += self.vector[1]

Then we are blitting the projectile at the rects coords.

Answer

To compute a direction you just need subtraction, and ideally normalisation.

self.vector = (mouse.position - player.position).normalize()

Note that your loop update should take the velocity and time between two frames into account:

self.rect.x += speed * timestep * self.vector[0]

self.rect.y += speed * timestep * self.vector[1]

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