Java-Gaming.org Hi !
 Featured games (83) games approved by the League of Dukes Games in Showcase (542) Games in Android Showcase (133) games submitted by our members Games in WIP (604) games currently in development
 News: Read the Java Gaming Resources, or peek at the official Java tutorials
Pages: [1]
 ignore  |  Print
 2D vectors and rotation.  (Read 4369 times) 0 Members and 1 Guest are viewing this topic.
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?
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().
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
 1  2  3  4  5  6  7  8  9  10  11  12  13 `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.

 Add your game by posting it in the WIP section, or publish it in Showcase. The first screenshot will be displayed as a thumbnail.
 Elsealabs (15 views) 2014-12-28 10:39:27 CopyableCougar4 (19 views) 2014-12-28 02:10:29 BurntPizza (24 views) 2014-12-27 22:38:51 Mr.CodeIt (14 views) 2014-12-27 04:03:04 TheDudeFromCI (19 views) 2014-12-27 02:14:49 Mr.CodeIt (26 views) 2014-12-23 03:34:11 rwatson462 (58 views) 2014-12-15 09:26:44 Mr.CodeIt (47 views) 2014-12-14 19:50:38 BurntPizza (96 views) 2014-12-09 22:41:13 BurntPizza (115 views) 2014-12-08 04:46:31
 Rayvolution 51x BurntPizza 30x basil_ 29x HeroesGraveDev 25x LiquidNitrogen 21x appel 18x kpars 18x KevinWorkman 15x Riven 15x princec 14x NegativeZero 13x pitbuller 13x gouessej 13x Spasi 12x SHC 12x KudoDEV 12x
 How do I start Java Game Development?by gouessej2014-12-27 19:41:21Resources for WIP gamesby kpars2014-12-18 10:26:14Understanding relations between setOrigin, setScale and setPosition in libGdx2014-10-09 22:35:00Definite guide to supporting multiple device resolutions on Android (2014)2014-10-02 22:36:02List of Learning Resources2014-08-16 10:40:00List of Learning Resources2014-08-05 19:33:27Resources for WIP games2014-08-01 16:20:17Resources for WIP games2014-08-01 16:19:50
 java-gaming.org 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‑gaming.org