Java-Gaming.org    
Featured games (81)
games approved by the League of Dukes
Games in Showcase (497)
Games in Android Showcase (114)
games submitted by our members
Games in WIP (563)
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  
  Rotating a point around a center point algorithm  (Read 852 times)
0 Members and 1 Guest are viewing this topic.
Offline lcass
« Posted 2013-10-22 20:01:04 »

Hi, Im looking for an algorithm that can rotate a pixel, ie move a pixel from x,y to newx,newy based on a given angle(most likely not 0,90,180,270,360) I have seen it somewhere i just cant remember the math behind it.
Offline moogie

JGO Knight


Medals: 12
Projects: 6
Exp: 10 years


Java games rock!


« Reply #1 - Posted 2013-10-22 20:49:56 »

surely you mean trigonometry?

newX=x+Math.cos(rad)*distance
newY=y+Math.sin(rad)*distance

or around a given origin (centre point)

distance=Math.sqrt((x-originX)*(x-originX)+(y-originY)*(y-originY));
startAngle=Math.atan2(x-originX,y-originY);
endAngle=startAngle+rad;
newX=originX+Math.cos(endAngle)*distance
newY=originy+Math.sin(endAngle)*distance

Note that this is untested and from memory of math from school over 14 years ago so it may be incorrect Tongue
Offline PaidGEEK

Senior Member


Medals: 5
Projects: 3


twitter.com/PaidGEEK


« Reply #2 - Posted 2013-10-22 20:51:11 »

Or like this:
To rotate a point 'p' around another point/origin 'c' simply subtract c from p, then rotate p and add c.

p.x -= c.x
p.y -= c.y

newx = p.x * cos(angle) - p.y * sin(angle)
newy = p.x * sin(angle) + p.y * cos(angle)

p.x = newx + c.x
p.y = newy + c.y

Improvisational programmer.
Games published by our own members! Check 'em out!
Legends of Yore - The Casual Retro Roguelike
Offline lcass
« Reply #3 - Posted 2013-10-23 14:56:26 »

Exactly what i was looking for thanks! this will really help me with my 3d engine.
Offline lcass
« Reply #4 - Posted 2013-10-24 19:22:24 »

How would I apply this to three d? Say I have point xyz wanting to rotated around point pxpypz?
Offline Abuse

JGO Knight


Medals: 12


falling into the abyss of reality


« Reply #5 - Posted 2013-10-24 21:23:49 »

How would I apply this to three d? Say I have point xyz wanting to rotated around point pxpypz?


Exactly the same principle; you just rotate around an axis of your choosing, rather than a point.

Make Elite IV:Dangerous happen! Pledge your backing at KICKSTARTER here! https://dl.dropbox.com/u/54785909/EliteIVsmaller.png
Offline relminator
« Reply #6 - Posted 2013-10-25 01:44:09 »

How would I apply this to three d? Say I have point xyz wanting to rotated around point pxpypz?


www.rel.phatcode.net/mytutes/3dtutes/chapter2/chapter2.htm

But I'd rather you use matrices:

www.rel.phatcode.net/mytutes/3dtutes/chapter4/chapter4.htm
Offline DrZoidberg

Senior Member


Medals: 15



« Reply #7 - Posted 2013-10-26 10:44:24 »

Here is an example of a rotation matrix. It can be used to rotate a vector around any arbitary axis.
http://pastebin.com/Gq4mHL82
Offline Roquen
« Reply #8 - Posted 2013-10-26 13:06:16 »

Keep things simple.  A rotation is one way to describe how one choice of a coordinate frame is related to some other.  In the case of a rotation and matrices, then the matrix describes how the orthonormal basis (the X,Y & Z axis directions) change...which is a parallel projection...so in the 3D, 3x3 matrix form each row (or column depending on choice of convention) is 'dotted' with the input to project from one to the other.  So each source direction is dotted with the target direction (you so have 3 equations) to get the output.   Humm...that was probably as clear as mud. Smiley
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.

UprightPath (20 views)
2014-09-20 20:14:06

BurntPizza (26 views)
2014-09-19 03:14:18

Dwinin (40 views)
2014-09-12 09:08:26

Norakomi (70 views)
2014-09-10 13:57:51

TehJavaDev (95 views)
2014-09-10 06:39:09

Tekkerue (49 views)
2014-09-09 02:24:56

mitcheeb (70 views)
2014-09-08 06:06:29

BurntPizza (52 views)
2014-09-07 01:13:42

Longarmx (39 views)
2014-09-07 01:12:14

Longarmx (45 views)
2014-09-07 01:11:22
List of Learning Resources
by Longor1996
2014-08-16 10:40:00

List of Learning Resources
by SilverTiger
2014-08-05 19:33:27

Resources for WIP games
by CogWheelz
2014-08-01 16:20:17

Resources for WIP games
by CogWheelz
2014-08-01 16:19:50

List of Learning Resources
by SilverTiger
2014-07-31 16:29:50

List of Learning Resources
by SilverTiger
2014-07-31 16:26:06

List of Learning Resources
by SilverTiger
2014-07-31 11:54:12

HotSpot Options
by dleskov
2014-07-08 01:59:08
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
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!