Chipmunk Physics

Code: Select all

- (void) calculateShotForTarget:(CGPoint)target from:(CGPoint)launchPos
{
	float x = target.x = launchPos.x;
	float y = target.y = launchPos.y;
	float g = 9.8;
	float v = 100; // this will be picked at random from a range
	float angle1, angle2;
	
	float tmp = pow(v, 4) - g * (g * pow(x, 2) + 2 * y * pow(v, 2));
	
	if(tmp < 0){
		NSLog(@"No Firing Solution");
	}else{
		angle1 = atan2(pow(v, 2) + sqrt(tmp), g * x);
		angle2 = atan2(pow(v, 2) - sqrt(tmp), g * x);
	}
	
	// Does anyone know what this does? I thought it may be the answer.
	//cpVect angleCPV = cpvforangle(angle1);
	
	angle1 = angle1 * (180 / M_PI);
	angle2 = angle2 * (180 / M_PI);
		
	// Get the horizontal and vertical velocities
	float vVel = v * sin(angle2);
	
	float hVel = v / tan(angle2);
	
	CGPoint force = cpv(hVel, vVel);
	
        // LaunchData is a convenience class for passing CGPoints around. 
	LaunchData *shot = [[[LaunchData alloc] initWithForce:force andPosition:launchPos] autorelease];
	[[NSNotificationCenter defaultCenter] postNotificationName:PlayerDidFinishAiming object:shot];

	
}

Code: Select all

// The X velocity is a fixed value
l_vel.x = m_rockVel.x;
// - Get gravity
getPhysicalWorld()->getGravity(l_gx,l_gy);

// Calc time in the air based on traveling to the player
// at the ROCKVEL_X speed and accounting for gravity (which
// may have a horizontal component
//
// s = ut + 1/2at^2
// s = distance to player (l_playerPos[0])
// u = horizontal vel (l_v.x)
// a = horizontal gravity (l_gx)
// t = time in air => at^2 + 2ut -2s = 0
// Solve the quadratic
// => t = ( -2u +- sqrt(4u^2 + 8as) ) / 2a

float l_bSqrMinus4ac = 4*l_v.X*l_v.X + 8*l_gx*l_playerPos[0];
float l_minus2u = -2*l_v.x;
float l_timeInAir = (l_gx) ? (l_minus2u + sqrt(l_bSqrMinus4ac)) / (2*l_gx) : l_playerPos[0]/l_v.x;

// Calc vertical speed so that for given time in air it will reach the player
//
// s = ut + 1/2at^2
// s = 0 (player is at same Y, so distance travel up == distance travel down => distance change = 0)
// u = vertical vel to calculate
// a = vertical gravity (l_gy)
// t = time in air (calculated above)
// => u = (0 - 1/2at^2)/t
l_v.y = (0 - 0.5*l_gy*l_timeInAir*l_timeInAir) / l_timeInAir;