## OpenGL "Coordinates"

Tutorials concerning the OpenGL® ES cross-platform API for full-function 2D and 3D graphics on the Google-Android platform.

### OpenGL "Coordinates"

Hey all,

I've been developing for android for a couple of weeks now, creating some simple apps using menus and buttons etc. That is getting quite boring without any inspiration, so I thought I'd give OpenGL a go.

The plan is to create a digital version of a quite entertaining game we play at school when there's nothing else to do, the goal is to capture as many squares. Just click the link below to see what I mean.
http://blogsimages.skynet.be/images_v2/ ... 074dd8.gif

I've managed to render a couple of cubes that I will eventually use to create a grid, I chose cubes as I thought I'd be able to create some nice effects with them. A game field would consist of 100 cubes to form a grid.

The problem is the coordinate system, I developed for the NDS (in C). There I would simply put a cube at (0, 0) and another one at (5, 0) etc. (0, 0) being the top left of the screen.

It's probably my logic, but I can't figure it out. Please point me in the right direction

Quipeace
Quipeace
Developer

Posts: 27
Joined: Tue Feb 23, 2010 4:00 pm

Unless you want to implement some 3d animations, I would recommend using android 2d graphics - painting on a canvas - for your game (create some "fake" 3d effect if you want)

For the following reasons :
- you dont need the speed of openGL
- its way easier to code
- you will probably get into troubles with picking. (i assume you want the border pieces to be clickable)

On a 2d canvas your 0,0 coordinates will be your top left corner.

As far as openGl is concerned the coords will depend on where you place the camera. In most examples and tutorials 0,0 will be the center of the screen.

just my 2 cents

Paul
pmws
Developer

Posts: 37
Joined: Thu Sep 24, 2009 12:23 pm

Yeah, I suppose 2d would work well, if not better. Just thought it would be a good project to get started with 3d programming .

I'll look into 2d first, see if I can figure that out first. I can always come back later.

Thanks

EDIT: NVM
Last edited by Quipeace on Wed Mar 10, 2010 6:34 pm, edited 1 time in total.
Quipeace
Developer

Posts: 27
Joined: Tue Feb 23, 2010 4:00 pm

Quipeace
Developer

Posts: 27
Joined: Tue Feb 23, 2010 4:00 pm

2D OpenGL, Match screen coordinates to world coordinates:

http://www.anddev.org/opengl_2d_match_o ... t8840.html
Skywhy
Developer

Posts: 35
Joined: Tue Oct 20, 2009 7:55 pm

That was what I was looking for, I'm too busy with school to actively develop at the moment, but it will certainly come in handy later.

Thanks
Quipeace
Developer

Posts: 27
Joined: Tue Feb 23, 2010 4:00 pm

You are quite welcome, happy to help if I can.
Skywhy
Developer

Posts: 35
Joined: Tue Oct 20, 2009 7:55 pm