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Offline StumpyStrust
« Posted 2012-03-07 08:47:13 »

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?


Offline theagentd
« Reply #1 - Posted 2012-03-07 08:48:53 »

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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;

Myomyomyo.
Offline Danny02
« Reply #2 - Posted 2012-03-07 10:00:26 »

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.
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Offline ReBirth
« Reply #3 - Posted 2012-03-07 12:58:01 »

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

Online ra4king

JGO Kernel


Medals: 345
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I'm the King!


« Reply #4 - Posted 2012-03-07 13:00:28 »

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

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

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

Offline Roquen
« Reply #5 - Posted 2012-03-07 13:53:28 »

Repeat to yourself: radians are your friend, degrees are for artist....
Offline theagentd
« Reply #6 - Posted 2012-03-07 14:13:11 »

Ugh, too much OpenGL for me... xD

Myomyomyo.
Offline StumpyStrust
« Reply #7 - Posted 2012-03-07 14:17:09 »

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.

Offline DiEvAl

Junior Newbie





« Reply #8 - Posted 2012-03-07 15:30:03 »

Repeat to yourself: radians are your friend, degrees are for artist....
Degrees are for openGL ;-)



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.
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.
Online ra4king

JGO Kernel


Medals: 345
Projects: 3
Exp: 5 years


I'm the King!


« Reply #9 - Posted 2012-03-07 16:56:39 »

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.

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Offline StumpyStrust
« Reply #10 - Posted 2012-03-08 07:37:41 »

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


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

Online ra4king

JGO Kernel


Medals: 345
Projects: 3
Exp: 5 years


I'm the King!


« Reply #11 - Posted 2012-03-08 22:27:15 »

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

Offline StumpyStrust
« Reply #12 - Posted 2012-03-09 03:19:25 »

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.



Offline theagentd
« Reply #13 - Posted 2012-03-09 08:59:24 »

Nice! =D

Myomyomyo.
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