Joystick and Jump problem

[rensu]

Hey guys

I need some advice

I have a very basic game in development and I am at the stage where I need to create a UI Joystick to control the main character. My idea is to have a circle for where your thumb will be placed. Around the circle is a small ball which goes around the circumference of the circle. This is to set the angle at which the play will jump. Can some one give me some advice as where to start and what to look into to achieve this .

My second problem is im not too sure how to add gravity to my game .

At the moment i have a collision detection which checks to see if the player is on a platform and if hes not then he continues to fall at a constant rate. WHen the player touches the screen the player needs to jump but at the moment he just teleports 20 pixels up into the air. How can I make it so the players sprite jumps realistically.

im not looking for code more advice and what to research into but any code would be greatly appreciated.

[dany_dev]

Originally Posted by rensu

Hey guys

I need some advice

I have a very basic game in development and I am at the stage where I need to create a UI Joystick to control the main character. My idea is to have a circle for where your thumb will be placed. Around the circle is a small ball which goes around the circumference of the circle. This is to set the angle at which the play will jump. Can some one give me some advice as where to start and what to look into to achieve this .

My second problem is im not too sure how to add gravity to my game .

At the moment i have a collision detection which checks to see if the player is on a platform and if hes not then he continues to fall at a constant rate. WHen the player touches the screen the player needs to jump but at the moment he just teleports 20 pixels up into the air. How can I make it so the players sprite jumps realistically.

im not looking for code more advice and what to research into but any code would be greatly appreciated.

I advice you to use Cocos2d, and for collision\gravity use Chipmunk (or Box2d) that are physics engine
cocos2d for iPhone

I started using it recently and it is awesome, a great framework for 2d game developing on iphone

it include also a template to start using Chipmunk and Box2d. More info on cocos2d's forum and Chipmunk\Box2d 's forum. You can see Documentation and Forum as sources, if you want to support the author and speed up the learning process consider to buy Sapus Tongue Source Code (written by cocos2d's founder), you can see more info in cocos2d's site.

For Joystick you can use it
[joystick] SneakyJoystick 0.1! cocos2d for iPhone
I think that i will replace my own Joystick class with it, it is complete and flexible

Basically for a jump you will apply a force perpendicular to X axis, but it is not usefull that i post code, because you need to start reading about cocos2d and then about chipmunk (Scene, CCLayer, schedule, CCsprite , cpBody, cpShape and other arguments.)

Good Luck!

[Kalimba]

For your virtual joystick, consider what you've got to work with:

• The "joystick" has a (usually fixed) position on screen. Specifically, there is a joystick center at some (Jx, Jy) on the screen
• The user will have her finger/thumb somewhere around the joystick center, at (Tx, Ty), indicating the direction she wishes to move.
• You know the value of (Jx, Jy), and track (Tx, Ty) because you're a good programmer and you know how to listen for touch events in your game.
• You can calculate the vector from the joystick center to the thumb location with a simple calculation Dx = Tx- Jx, Dy = Ty - Jy.
• Once you have (Dx, Dy), obtaining an angle is trivial, using the arctangent function atan2().

[Mr Jack]

Originally Posted by rensu

My second problem is im not too sure how to add gravity to my game .

At the moment i have a collision detection which checks to see if the player is on a platform and if hes not then he continues to fall at a constant rate. WHen the player touches the screen the player needs to jump but at the moment he just teleports 20 pixels up into the air. How can I make it so the players sprite jumps realistically.

Rather than falling at a constant rate, store the fall rate in a variable, let's call it velocityY. Every frame rather than adding your constant value, add velocityY. Then reset velocityY to zero if there's a collision and otherwise take a fixed value to represent gravity off it each frame.

Gravity in the real world produces acceleration rather than a constant movement so this will lend a more realistic effect. It also neatly solves your jump problem, because you can simply set velocityY to a suitable positive value when you press jump and the gravity modification on each frame will produce the correct parabolic jump.