How do I make a projected line for pool/billard game?

Hey guys.

I can't get it together.

This is how my game currently looks

i.imgur.com/oR2SjIE.png

What I wanted to do is show a projected line for the red ball (white short line). So If change the angle the line should show the direction the red ball goes to. I thought it would be easy but I just don't know how to do it.

I think something like calculate the angle the balls are hitting each other to calculate their direction?

Ignore the green line, its just to check collision with any red ball.

Would be nice if someone has an idea which I could may understand :D

Regards,

Kraudi

Thank you very much R0J0hound

I tried doing it with the loop and it works but it's very inacurate. DOn't know If I've made some mistake but you can have a look in the demo here.

polyth-game.com/builds/snooker

(You can move red balls with pressed right mouse)

Also this is the code I've made.

i.imgur.com/WOWk561.png

I've also added more collision points to the red balls so it is more accurate but doesn't changed much.

Ok I changed some stuff it is definitely more accurate. I did it with 'move 1px forward" you mentioned.

Heres the v2 demo

polyth-game.com/builds/snooker2

Though it's still not good enough because if you play the red ball just thinly the line indicates that you will not hit the ball. Nevertheless the white ball still hits the red ball in the end so that means some calculation is not 'good enough'. Also the shot line sometimes goes the wrong way.

If you have some minutes would you mind looking into the c3 file itself if I share em?

Regards and tnx!

Kraudi there's a technique called Signed Distance Fields ( SDF ) which you could use here to help you. The basic idea is that you have a function that returns the distance from any position to the closest point on the surface of an object. If the position is inside the object then the distance is negative ( hence "Signed" distance fields ). Circles are probably the easiest SDF, and by the looks of it you only need circles. So that's convenient! Here's the function for a circle written in JS, it's mostly simple maths so should be easy enough to read.

function circleSDF (point_x, point_y, center_x, center_y, radius) {
	let dx = point_x - center_x;
	let dy = point_y - center_y;
	return Math.sqrt(dx * dx + dy * dy) - radius;
}

function distance_to_closest_ball (cueball) {
	let smallest_distance = Infinity;

	for (const ball of balls) {
		let distance = circleSDF(cueball.x, cueball.y, ball.x, ball.y, cueball.radius + ball.radius);

		if (distance < smallest_distance) {
 			smallest_distance = distance;
 		}
 	}

 	return smallest_distance;
}