Im drawing a circle on html canvas, the circle is meant to indicate a "ship".
I have the current position (x, y) of the "Ship" object and randomly determine a degree (0 to 360) and an amount value. I then want to alter the ship's current position by the degree and amount.
i.E. ship is currently at 100/100 (on a canvas). I determine degree as 30 and amount as 50.
Now i would like to get the ships new location based on the assumption that 0 degree would indicate "straight up" and 180 degree would indicate straight down while 50 amount indicate a movement of 50 Pixels into the direction determined.
I know it has something to do with Radians, but unfortunally im unable to solve it further.
var ship = {
x: 100,
y: 100
}
var movement = {
degrees: 30,
amount: 50
}
Yes, all angles in JavaScript are in radians. In addition, the canvas context has 0° point to the right so you need to subtract 90° from all angles if you want 0° to be straight up:
var angle = (movement.degrees - 90) / 180 * Math.PI; // compensate angle -90°, conv. to rad
ship.x += movement.amount * Math.cos(angle); // move ship
ship.y += movement.amount * Math.sin(angle);
var movement = {
degrees: 30,
amount: 50
}
var ctx = document.querySelector("canvas").getContext("2d");
(function loop() {
ctx.clearRect(0, 0, 300, 150);
var ship = { // reset ship position for demo
x: 100,
y: 90
}
ctx.strokeRect(ship.x - 2, ship.y - 2, 4, 4);
ctx.fillText("From", ship.x + 5, ship.y);
var angle = (movement.degrees - 90) / 180 * Math.PI; // compensate angle -90°, conv. to rad
ship.x += movement.amount * Math.cos(angle); // move ship
ship.y += movement.amount * Math.sin(angle);
ctx.strokeRect(ship.x - 2, ship.y - 2, 4, 4);
ctx.fillText(movement.degrees + "°", ship.x + 5, ship.y);
movement.degrees++;
movement.degrees = movement.degrees % 360;
requestAnimationFrame(loop);
})();
<canvas></canvas>