Random Direction

Game Mechanics
#1

How would I find a random direction to send an object flying towards? Say I want to send an object flying towards 56 degrees how can I actually move an object in the x and y plane to that direction? Normally I would just have a x speed and y speed but when i make a random explosion effect I get a square.

1 1 1 1 1
1 1
1 0 1
1 1
1 1 1 1 1

0 is the origin of the explosion.

I want

1

1 1
1 0 1
1 1
1

Can I just find a random number between 360 and send the object in that direction?

#2 

double angle = 10; //The shot angle
double moveSpeed = 10; //The speed of the shot

double xSpeed = Math.cos(angle) * moveSpeed;
double ySpeed = Math.sin(angle) * moveSpeed;
#3

and also remember in which unit youj have your angles, radient or gradient. The MAth.* functions take radient i gues(?), take a look at the docs.

#4

repeat theagentd’s code with diff angle value. for explosion fixed length can work too.

#5

Yeah careful all the trig functions in the Math class use radians.


double angle = Math.random() * 2 * Math.PI;
double speed = 20;

double dX = speed * Math.cos(angle);
double dY = speed * Math.sin(angle);
#6

Repeat to yourself: radians are your friend, degrees are for artist…

#7

Ugh, too much OpenGL for me… xD

#8

Thank you so much exactly what I was looking for…well I knew I wanted to find the radians of the angle with sin/cos but could not remember what to do with them. How much slower is this compared to just giving and x and y speed? Is the sin/cos that costly? I know you are not doing it on every move update but still.

#9

Degrees are for openGL :wink:

If your computer is over 30 years old or if you have millions of objects, it may be costly. Otherwise you will not notice any slowdown.

#10

If you are worried about performance, it is best to use this FastMath class, courtesy of Riven. This uses a lookup table, causing the trig functions to be over 50x faster.

#11

This was what I was looking for but I am still getting a square. :o
Am I doing this wrong?

double speedX = 10Math.cos(angle);
double speedY = 10Math.sin(angle);

#12

Are you using 2 different angles for cos and sin? That’s the only possible way to get a square :wink:

#13

No same angle but i forgot the pi…no pun intended. I got it working now and it is looking really freaking good…at least to me it is.

#14

Nice! =D