Java-Gaming.org Hi !
 Featured games (83) games approved by the League of Dukes Games in Showcase (521) Games in Android Showcase (127) games submitted by our members Games in WIP (589) games currently in development
 News: Read the Java Gaming Resources, or peek at the official Java tutorials
Pages: [1]
 ignore  |  Print
 (SOLVED) Problem with perspective  (Read 563 times) 0 Members and 1 Guest are viewing this topic.
SimonH
 « Posted 2012-12-21 19:31:03 »

Hi Folks,

Can anyone help me with a maths problem I've come up against?
I'm drawing a perspective view of an image so I'm converting screen coordinates to a perspective point on a plane, like so;

tx=screen_x-screen_width/2
ty=screen_y-screen_height/2
tz=(ty+250)/zScale
plane_x=tx*(d/tz)
plane_y=ty*(d/tz)

Sort of ray-casting. This works fine.
My problem arises when I want to reverse the process; to find the screen coordinates for any given coordinates on the plane.
I've covered sheets of paper with scribblings but I can't seem to get it right!
Can anyone point me in the right direction?

People make games and games make people
ra4king

JGO Kernel

Medals: 355
Projects: 3
Exp: 5 years

I'm the King!

 « Reply #1 - Posted 2012-12-21 20:13:58 »

So to go from plane_x,plane_y to screen_x,screen_y?

Considering 'd' and 'zscale' are also knowns, then:

screen_y = (d*zscale*(screen_height/2) - plane_y * (screen_height/2) + plane_y * 250) / (d*zscale - plane_y)
screen_x = (plane_x * (screen_y - (screen_height/2) + 250))/(zscale * d) + screen_width/2

EDIT: And the work painstakingly "drawn" in Paint.NET:

SimonH
 « Reply #2 - Posted 2012-12-22 02:04:54 »

I haven't checked this through thoroughly yet but it looks pretty good to me!
Ra4King you are a star! Many thanks!

Edit: Works a treat - hopefully you'll get to see it in action shortly!

People make games and games make people
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.
 xFryIx (58 views) 2014-11-13 12:34:49 digdugdiggy (37 views) 2014-11-12 21:11:50 digdugdiggy (30 views) 2014-11-12 21:10:15 digdugdiggy (24 views) 2014-11-12 21:09:33 kovacsa (48 views) 2014-11-07 19:57:14 TehJavaDev (51 views) 2014-11-03 22:04:50 BurntPizza (51 views) 2014-11-03 18:54:52 moogie (66 views) 2014-11-03 06:22:04 CopyableCougar4 (65 views) 2014-11-01 23:36:41 DarkCart (150 views) 2014-11-01 14:51:03
 theagentd 29x basil_ 27x BurntPizza 23x princec 17x Spasi 17x pitbuller 15x kpars 14x HeroesGraveDev 14x Riven 14x KevinWorkman 13x SHC 11x Grunnt 11x gouessej 10x Nate 9x kevglass 9x Longarmx 9x
 Understanding 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 16:19:50List of Learning Resources2014-07-31 16:29:50List of Learning Resources2014-07-31 16:26:06
 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