Throw ball using cocos2d but without any physic engine - iphone

Question

I want to throw a ball with swipe speed but do not want to use any physic engine. so please can any one suggest me how i do this.
thanks

Answer 1

A simple yet effective approach without having to explicitly use any physics engine is to step the velocity and position of the ball sprite manually in your update loop, Euler-style.
In the typical case (with downward gravity), you will have non-constant velocity in the y-direction and constant velocity in the x-direction, hence the following code:
-(void) update: (ccTime) dt
{
// Step only the y-velocity
velocity_y += GRAVITY * dt;
// Step the position values and update the ball sprite position accordingly
ball.position.x += velocity_x * dt;
ball.position.y += velocity_y * dt;
}
Then when a swipe event is detected,
Capture the swipe velocity (you will have to compute the change in position of the finger touch in the current and last frame)
Multiply the velocity with a scaling factor if necessary.
Set *velocity_x* and *velocity_y* to these initial values.

Answer 2

I am using projectile motion formulas to do this, http://en.wikipedia.org/wiki/Projectile_motion, along with cocos actions. Here you have a possible approach:
First
Implement a CCActionInterval subclass that receives the projectile formula parameters and updates the projectile position. In this case, ProjectileAction. These are the key methods you need to over-ride:
-(void) startWithTarget:(id)target
{
self.initialPosition = [target position];
self.elapsedTime = 0;
[super startWithTarget:target];
}
-(void) update: (ccTime) tt
{
self.elapsedTime += tt;
float t = self.elapsedTime;
float theta = CC_DEGREES_TO_RADIANS(self.angle);
float v0 = self.velocity;
float g = self.gravitationalAcceleration;
double x = v0 * cos(theta) * t;
double y = v0 * sin(theta) * t - 0.5 * g * t * t ;
[self.target setPosition: ccp(self.initialPosition.x + (float)x, self.initialPosition.y + (float)y)];
}
Second
Use your swipe gesture to recognize the speed, that will translate to the ball's initial velocity in the equation above and to the theVelocity parameter bellow. I leave that part to you.
Third
Run the action. i.e.
ProjectileLaunch* action = [ProjectileLaunch actionWithDuration:10
angle:45
initialVelocity:theVelocity
g:9.8];
[sprite runAction:action];
I hope this helps you.
Regards.