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 Basic question, a beginner !  (Read 2898 times) 0 Members and 1 Guest are viewing this topic.
alvaro

Junior Newbie

Java games rock!

 « Posted 2003-11-10 06:40:41 »

Hi,

can somebody tell me when this formula can be used, where can I get more information about it?

dir_x =  Math.cos(alpha*(Math.PI/180));
dir_y =  Math.sin(alpha*(Math.PI/180));
....

ball.pos_x+=dir_x ...
ball.pos_y+=dir_y ...

regards
Alvaro

Orangy Tang

JGO Kernel

Medals: 56
Projects: 11

 « Reply #1 - Posted 2003-11-10 06:58:39 »

Looks like an equation to generate a unit circle, what do you actually want it to do?

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Herkules

Senior Devvie

Friendly fire isn't friendly!

 « Reply #2 - Posted 2003-11-10 07:02:00 »

You use it when calculating the x/y translation when you have a angle of direction given in degrees [0,360].

Did I get the question right?

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Orangy Tang

JGO Kernel

Medals: 56
Projects: 11

 « Reply #3 - Posted 2003-11-10 07:12:09 »

Oh  yeah, convert an angle to a vector, that makes more sense. I had assumed that the alpha meant it was being interpolated over, instead its actually an input angle.

Guessing the question is still the tricky part though

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cfmdobbie

Senior Devvie

Medals: 1

Who, me?

 « Reply #4 - Posted 2003-11-10 12:48:43 »

Okay, while we're playing some kind of bizzare Jeopardy, try this:

Programmer Tom is writing some code and uses the decimal number 1597463007.  What is his method likely intended to do?

Hellomynameis Charlie Dobbie.
kevglass

« JGO Spiffy Duke »

Medals: 221
Projects: 24
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Coder, Trainee Pixel Artist, Game Reviewer

 « Reply #5 - Posted 2003-11-10 16:19:04 »

Random number generator

Kev

Jeff

JGO Coder

Got any cats?

 « Reply #6 - Posted 2003-11-10 17:25:23 »

Thats fundemental trig.  Try any trigonometry textbook.

Alpha is your angle of direction in degrees.  pi/180 is a conversion from degress to radians, which is what all of the trig functions want.

sin == opposite/hypotenuse == Y part of that angle (assuming a total movement of 1,  hypotenuse is actually the total distance moved, opposite is the Y component.)  Note that this assumes a
trig style coordinate system where poitive Y is at the top and negative Y at the bottom.  if you are working in screen space you'll need to reverse it.

cos == adjacent/hypotenuse == X part of that component.

So your simple answer is. given a ship position x,y  and angle of motion alpha,  that math calculates the new position if the ship moves 1 unit in alpha direction.

Basic trig.  if you can't handle this you will have a LOT of "fun" trying to write game code....

Got a question about Java and game programming?  Just new to the Java Game Development Community?  Try my FAQ.  Its likely you'll learn something!

http://wiki.java.net/bin/view/Games/JeffFAQ
Jeff

JGO Coder

Got any cats?

 « Reply #7 - Posted 2003-11-10 17:28:56 »

Btw...

This question has nothing to do with physcis and really belongs in "Newless Clubies" which is our total beginner topic.

Got a question about Java and game programming?  Just new to the Java Game Development Community?  Try my FAQ.  Its likely you'll learn something!

http://wiki.java.net/bin/view/Games/JeffFAQ
alvaro

Junior Newbie

Java games rock!

 « Reply #8 - Posted 2003-11-11 10:54:51 »

regards

Jeff

JGO Coder

Got any cats?

 « Reply #9 - Posted 2003-11-12 00:43:48 »

JK

Got a question about Java and game programming?  Just new to the Java Game Development Community?  Try my FAQ.  Its likely you'll learn something!

http://wiki.java.net/bin/view/Games/JeffFAQ
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