Hi !
Featured games (91)
games approved by the League of Dukes
Games in Showcase (800)
Games in Android Showcase (237)
games submitted by our members
Games in WIP (867)
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 8855 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 Ninja

Medals: 16
Projects: 6
Exp: 10 years

Java games rock!

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

surely you mean trigonometry?


or around a given origin (centre point)


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

Java4k RIP 2014
Offline PaidGEEK

Senior Devvie

Medals: 5
Projects: 3

« 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 Ninja

Medals: 71

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.
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?

But I'd rather you use matrices:
Offline DrZoidberg

JGO Coder

Medals: 21

« 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.
Offline Roquen

JGO Kernel

Medals: 518

« 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 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  

Riven (348 views)
2019-09-04 15:33:17

hadezbladez (5132 views)
2018-11-16 13:46:03

hadezbladez (2013 views)
2018-11-16 13:41:33

hadezbladez (5400 views)
2018-11-16 13:35:35

hadezbladez (1121 views)
2018-11-16 13:32:03

EgonOlsen (4539 views)
2018-06-10 19:43:48

EgonOlsen (5396 views)
2018-06-10 19:43:44

EgonOlsen (3083 views)
2018-06-10 19:43:20

DesertCoockie (3977 views)
2018-05-13 18:23:11

nelsongames (4527 views)
2018-04-24 18:15:36
A NON-ideal modular configuration for Eclipse with JavaFX
by philfrei
2019-12-19 19:35:12

Java Gaming Resources
by philfrei
2019-05-14 16:15:13

Deployment and Packaging
by philfrei
2019-05-08 15:15:36

Deployment and Packaging
by philfrei
2019-05-08 15:13:34

Deployment and Packaging
by philfrei
2019-02-17 20:25:53

Deployment and Packaging
by mudlee
2018-08-22 18:09:50

Java Gaming Resources
by gouessej
2018-08-22 08:19:41

Deployment and Packaging
by gouessej
2018-08-22 08:04:08 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!