Java-Gaming.org Hi !
 Featured games (90) games approved by the League of Dukes Games in Showcase (767) Games in Android Showcase (230) games submitted by our members Games in WIP (854) games currently in development
 News: Read the Java Gaming Resources, or peek at the official Java tutorials
Pages: [1]
 ignore  |  Print
 Scan if unit is visible to an other unit  (Read 2407 times) 0 Members and 1 Guest are viewing this topic.
P0jahn

Senior Devvie

Medals: 1
Projects: 3

 « Posted 2012-12-05 11:28:17 »

In my 2D game, the stage is an 2d char array.The values of the array is either 0, for solid(wall), or 1, for hollow.
So if unit stands on x:150 y:200, I want to check if he can "see" an other unit that stands on for example x: 450 y:300.
By "see" I mean there is not a wall(solid space) between them.

Any tips?
Varkas
 « Reply #1 - Posted 2012-12-05 11:44:44 »

Try a line algorithm, like Bresenhams, or just this:

http://en.wikipedia.org/wiki/Line_drawing_algorithm

Check if no square on the line is blocked. Then the units can see each other. Some line algorithms are unsymmetric, in that case you need to check both directions (lines from->to and to->from)

if (error) throw new Brick(); // Blog (german): http://gedankenweber.wordpress.com
saifix

Senior Newbie

Medals: 1

 « Reply #2 - Posted 2012-12-05 11:46:22 »

There are several examples of how to do this on: http://roguebasin.roguelikedevelopment.org/index.php?title=Field_of_Vision

You can use this code to check if a wall is in a units line of sight.
 1  2  3  4  5  6  7  8  9  10 `Unit u = ...;Vec2 direction = new Vec2(1, 0); // whatever direction the unit is facing, 1,0 = along the X axisVec2 searchPosition = u.position().clone();for(int i = 0; i < u.searchDistance /* how far should we cast a ray*/; i++) {     if(map[searchPosition.x][searchPosition.y] == 0) {         return true;     }     searchPosition.add(direction);}return false;`

If a wall is in the way this code will return true, if not it will return the opposite. With a few modifications you can make it check for another unit.
Orangy Tang

JGO Kernel

Medals: 57
Projects: 11

 « Reply #3 - Posted 2012-12-05 12:32:31 »

Try a line algorithm, like Bresenhams, or just this:

http://en.wikipedia.org/wiki/Line_drawing_algorithm

Check if no square on the line is blocked. Then the units can see each other. Some line algorithms are unsymmetric, in that case you need to check both directions (lines from->to and to->from)
Bresenhams is not really appropriate since it may jump over solid cells or around corners. A specific visibility algorithm (like the ones saifix linked to) give much better results.

I ended up adapting the Wolf3d cell scanning algorithm.

[ TriangularPixels.com - Play Growth Spurt, Rescue Squad and Snowman Village ] [ Rebirth - game resource library ]
P0jahn

Senior Devvie

Medals: 1
Projects: 3

 « Reply #4 - Posted 2012-12-05 16:09:52 »

Thanks for the code saifix. I will try to understand the code instead of just copy and paste.
Could you please give a more detailed explanation of the code? For instance, what is Vec2? The arg to direction, is that X Y coordinates to an object?

Also, your code just check a straight line, right?
saifix

Senior Newbie

Medals: 1

 « Reply #5 - Posted 2012-12-05 23:11:45 »

Thanks for the code saifix. I will try to understand the code instead of just copy and paste.
Could you please give a more detailed explanation of the code? For instance, what is Vec2? The arg to direction, is that X Y coordinates to an object?

Also, your code just check a straight line, right?

Vec2 is a vector made up of 2 components, x & y. The arguments are the direction which the casted ray is traveling in, if it were (-1, 0) it'd test a straight line starting going to the left of the unit and if it were (0, 1) it'd test a line traveling up from the unit.

Yes, it only checks a straight line.
Pages: [1]
 ignore  |  Print

 EgonOlsen (1278 views) 2018-06-10 19:43:48 EgonOlsen (1147 views) 2018-06-10 19:43:44 EgonOlsen (881 views) 2018-06-10 19:43:20 DesertCoockie (1291 views) 2018-05-13 18:23:11 nelsongames (1106 views) 2018-04-24 18:15:36 nelsongames (1337 views) 2018-04-24 18:14:32 ivj94 (2077 views) 2018-03-24 14:47:39 ivj94 (1230 views) 2018-03-24 14:46:31 ivj94 (2188 views) 2018-03-24 14:43:53 Solater (798 views) 2018-03-17 05:04:08
 Deployment and Packagingby mudlee2018-08-22 18:09:50Java Gaming Resourcesby gouessej2018-08-22 08:19:41Deployment and Packagingby gouessej2018-08-22 08:04:08Deployment and Packagingby gouessej2018-08-22 08:03:45Deployment and Packagingby philfrei2018-08-20 02:33:38Deployment and Packagingby philfrei2018-08-20 02:29:55Deployment and Packagingby philfrei2018-08-19 23:56:20Deployment and Packagingby philfrei2018-08-19 23:54:46
 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