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Asked: 2026-05-16T16:57:16+00:00

Background: I have 8 images for every sprite in my bird’s view JavaScript game,

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Background: I have 8 images for every sprite in my bird’s view JavaScript game, representing top, top-right, right, right-bottom etc., depending on the player’s space ship speed.

Question: Given the values sprite.speed.x and sprite.speed.y (which could be something like 4 and -2.5, or 2 and 0 for instance), how do I get the correct angle in degrees? Given that angle, I could then have a lookup for which degrees value represents which sprite image. Or perhaps there’s an even easier way. (Currently I’m just using something like “if x below zero use left image” etc. which will result in diagonal images used almost all of the time.)

Searching around, I found …

angle = Math.atan2(speed.y, speed.x);

… but somehow I’m still missing something.

PS: Zero speed can be ignored, these sprites will just use whatever was the last valid direction image.

Thanks so much for any help!

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1 Answer

  1. Editorial Team

    What you suggest is exactly right! Note that the result of Math.atan2 is in radians, and you’re probably more familiar with degrees; you can convert using angle_degrees = angle*(180./pi).

    (Note also that you don’t need to normalize as RCIX suggested, though you can if you want to. What you have, angle = Math.atan2(speed.y, speed.x);, should work just fine.)

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