Moving ball at constant rate with angle-CodePudding

I am coding a small game in JavaScript and I am running into a math problem. I am trying to move an object towards the location that I just clicked. I am able to successfully do this with the code below. However I am having difficulty figuring out how to make the velocity constant. If I click close to the object that I am shooting from, the difference in the X/Y is small so dx/dy is slow. If I click far away the dx/dy has high values, so it moves a lot faster.

Here is the code that I have so far.

let relativeXY = relMouseCord(e);
let rise = relativeXY[1] - pOne.posY; //<-- This is the distance between the Y coords
let run = relativeXY[0] - pOne.posX; //<-- This is the distance between the X coords

let angle = Math.atan2(rise,run)*180/Math.PI 
console.log('tan angle '   Math.tan(angle))
console.log('acutal angle '  angle)

bullet.x = pOne.posX
bullet.y = pOne.posY

tempdx = run * 0.02     //Math.cos(angle)
tempdy = rise * 0.02    //Math.sin(angle)

I attempted to use cos and sin to normalize the speed and was able to make the velocity constant, but the direction of the projectile was incorrect.

CodePudding user response：

normalize your direction vector (run,rise) to unit size:

tempdx = run  * 0.02 / sqrt((run*run) (rise*rise))
tempdy = rise * 0.02 / sqrt((run*run) (rise*rise))

or use goniometrics (but do not convert to [deg] as goniometrics expect [rad] !!!)

let angle = Math.atan2(rise,run)
console.log('tan angle '   Math.tan(angle))
console.log('acutal angle '  angle*180/Math.PI)
tempdx = cos(angle) * 0.02
tempdy = sin(angle) * 0.02

... assuming 0.02 is your wanted speed ...