Hi !
Featured games (90)
games approved by the League of Dukes
Games in Showcase (711)
Games in Android Showcase (213)
games submitted by our members
Games in WIP (785)
games currently in development
News: Read the Java Gaming Resources, or peek at the official Java tutorials
    Home     Help   Search   Login   Register   
Pages: [1]
  ignore  |  Print  
  2D vectors and rotation.  (Read 6192 times)
0 Members and 1 Guest are viewing this topic.
Offline RageMatrix

Senior Newbie

Java games rock!

« Posted 2010-03-04 09:55:51 »

I'm building a simple little vector game in 2D. I have a vector class which simply holds X and Y co-ordinates and have used three of these to create a little triangle spaceship. The co-ordinates are based about the arbitary origin posX and posY - which just happens to be the centre of the screen.

How do I go about rotating the points around this arbitary origin? Should I temporarily reset the posX and posY to (0,0) rotate and then move back to the arbitary origin or can I rotate the points where they are?
Offline Bonbon-Chan

JGO Coder

Medals: 12

« Reply #1 - Posted 2010-03-04 19:12:03 »

How I see it :
1) for the shape, store the coordinates around the (0,0) position
2) when rendering, rotate the shape first then translate it to the ship position.

By the way, java 2D allready have everything to deal with this. You can use for example GeneralPath to store shapes. Use AffinTransform to rotate/translate it. And then use a Graphics2D.draw().
Offline DzzD
« Reply #2 - Posted 2010-03-04 20:39:56 »

and if you want to rotate them by hand around an arbitrary axis :

angle : rotation angle in Radians
axisX : x pos for rotation center
axisY : y pos for rotation center
class VectorXXX
   double x;
   double y;
   public void rotate(double angle,double axisX,double axisY)
      double tY=y-axisX,tX=x-axisY;
      double cosa=Math.cos(angle);
      double sina=Math.sin(angle);
      x=tX*cosa + tY*sina + axisX;
      y=-tX*sina + tY*cosa + axisY;

NB: adapted from 3DzzD not tested but should work

Pages: [1]
  ignore  |  Print  
You cannot reply to this message, because it is very, very old.

Archive (92 views)
2017-02-27 19:41:49

Riven (83 views)
2017-02-27 17:26:59

numerical (450 views)
2017-02-21 07:32:16

numerical (455 views)
2017-02-21 07:31:46

theagentd (563 views)
2017-02-18 13:42:33

theagentd (559 views)
2017-02-18 13:35:16

h.pernpeintner (1735 views)
2017-01-24 22:39:11

h.pernpeintner (1689 views)
2017-01-24 22:38:32

Galdo (2271 views)
2017-01-12 13:44:09

Archive (2183 views)
2017-01-02 05:31:41
List of Learning Resources
by elect
2016-09-09 09:47:55

List of Learning Resources
by elect
2016-09-08 09:47:20

List of Learning Resources
by elect
2016-09-08 09:46:51

List of Learning Resources
by elect
2016-09-08 09:46:27

List of Learning Resources
by elect
2016-09-08 09:45:41

List of Learning Resources
by elect
2016-09-08 08:39:20

List of Learning Resources
by elect
2016-09-08 08:38:19

Rendering resources
by Roquen
2016-08-08 05:55:21 is not responsible for the content posted by its members, including references to external websites, and other references that may or may not have a relation with our primarily gaming and game production oriented community. inquiries and complaints can be sent via email to the info‑account of the company managing the website of java‑
Powered by MySQL Powered by PHP Powered by SMF 1.1.18 | SMF © 2013, Simple Machines | Managed by Enhanced Four Valid XHTML 1.0! Valid CSS!