Hi !
Featured games (85)
games approved by the League of Dukes
Games in Showcase (636)
Games in Android Showcase (178)
games submitted by our members
Games in WIP (685)
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  
  Moving from point A to B - Shooting and movement  (Read 843 times)
0 Members and 1 Guest are viewing this topic.
Offline SauronWatchesYou

JGO Knight

Medals: 29
Projects: 4
Exp: 7-9 months

Hi there! :)

« Posted 2014-07-06 07:57:54 »

Hi guys so i'm looking into making my enemy get the position of the player and then fire a bullet towards the previous location and was wondering what the best way to do this was. (My game is a 2D vertical scrolling game and the enemy shoots down towards the player)

I've searched online but i'm a little confused right now. People seem to suggest using trig and was wondering if anyone could point me in the right direction? A common piece of code I found was this:

double dx = player.x - enemy.x, dy = player.y - enemy.y;
double distance = Math.sqrt(dx*dx + dy*dy);

double multiplier = moveSpeedOfEnemy / distance;

double velocityX = dx * multiplier, velocityY = dy * multiplier;

I'll likely have to brush up my maths as this is confusing me but if anyone can explain exactly what I should do and any useful resources then it would be great! Smiley

Sorry if the question is a little vague but just ask if you need more info etc Cheesy

Thank you

Hey, you! Back to work
Offline PandaMoniumHUN

JGO Coder

Medals: 32
Exp: 3 years

White-bearded OGL wizard

« Reply #1 - Posted 2014-07-06 09:24:59 »

That's actually a pretty good code snippet you found there. Cheesy

To be honest you don't even need trigonometry for this, just the very basics of linear algebra, mostly vectors.
You can create a vector that points from point A to point B by subtracting all of A's components from all of B's components.
That's what
are in your code.
is just the distance formula to calculate the distance between the player and the enemy, and the
is there to make the projectile go faster as it gets closer to it's target. However, it's a really bad way of achieving acceleration and I wouldn't use that.

To make your enemies fire a bullet at your player's current position you should save the player's actual position (by value and not by reference) and calculate against that like so:
Vector2f direction = new Vector2f(target.x-position.x, target.y-position.y);
position.x += direction.x*speed*delta;
position.y += direction.y*speed*delta;

is just a Vector2f that contains your projectile's current position and
is a Vector2f too which contains the projectile's target location.
should be the speed of the projectile.

This is just the basics and the first thing that I would change on this code as soon as you understand what's going on is to add some kind of time based (and definitely not distance based) acceleration. Smiley

My Blog | Jumpbutton Studio - INOP Programmer
Can't stress enough: Don't start game development until you haven't got the basics of programming down! Pointing
Offline SauronWatchesYou

JGO Knight

Medals: 29
Projects: 4
Exp: 7-9 months

Hi there! :)

« Reply #2 - Posted 2014-07-07 07:27:05 »

Thanks Panda! Smiley I really appreciate the detailed response about what each thing is doing. I'm going to go over it a few more times just to make sure I understand it and then will mess around with the code Tongue

Hey, you! Back to work
Pages: [1]
  ignore  |  Print  
You cannot reply to this message, because it is very, very old.

Dwinin (58 views)
2015-11-07 13:29:08

Rems19 (72 views)
2015-10-31 01:36:56

Rems19 (63 views)
2015-10-31 01:32:37

williamwoles (101 views)
2015-10-23 10:42:59

williamwoles (87 views)
2015-10-23 10:42:45

Jervac_ (102 views)
2015-10-18 23:29:12

DarkCart (128 views)
2015-10-16 00:58:11

KaiHH (112 views)
2015-10-11 14:10:14

KaiHH (148 views)
2015-10-11 13:26:18

BurntPizza (162 views)
2015-10-08 03:11:46
Rendering resources
by Roquen
2015-11-13 14:37:59

Rendering resources
by Roquen
2015-11-13 14:36:58

Math: Resources
by Roquen
2015-10-22 07:46:10

Networking Resources
by Roquen
2015-10-16 07:12:30

Rendering resources
by Roquen
2015-10-15 07:40:48

Math: Inequality properties
by Roquen
2015-10-01 13:30:46

Math: Inequality properties
by Roquen
2015-09-30 16:06:05

HotSpot Options
by Roquen
2015-08-29 11:33:11 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!