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MoveTo or JumpTo using update function

pabitrapadhy

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Problem Description
Hi,
I am trying to achieve the same MoveTo action and JumpTo action but without using the Actions in cocos2d-x.

The reason for this is my game has wind effect and I need to alter the end location.

I’ve been through the source code of JumpBy update() and MoveBy update(), but i am not clear how do they do it.

I will give you an instance of what i want –

i know the start point and end point, (say start point contains a sprit and end point is the crosshair where i need to throw the target in trajectory path)

time from the start point to the crosshari is 1 second.

how can I achieve this.. !!
please help me.

Thank you in advance.

Sonar Systems admin

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Have you tried using actions but with easing as that may be able to replicate the wind effect when moving objects.

Kind regards

Sonar Team

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pabitrapadhy

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nope, that’s not what would do.

actually in my game I have a left to right / right to left wind effect with certain velocity

say with wind effect enabled each time the x value will be added with an offset of 1 in the update funciton itself.
I need to understand the logic behind JumpBy update function and how they do it with time.
when I use Jump by – i have the start and endpos so, i can calculate the height and the x difference

when i try it with JumpBy it works fine, but i am failing to understand the logic, that how it works.
could you please help me.. !!

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Sonar Systems admin

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MoveTo is easier to get around but JumpTo has a lot to it.

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pabitrapadhy

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yes.. basically i am trying to understand this piece of code.
in some easier terms

void JumpBy::update(float t)
	{
	// parabolic jump (since v0.8.2)
	if (_target)
	{
	float frac = fmodf( t * _jumps, 1.0f );
	float y = _height * 4 * frac * (1 - frac);
	y += _delta.y * t;

	float x = _delta.x * t;
	#if CC_ENABLE_STACKABLE_ACTIONS
	Vec2 currentPos = _target->getPosition();

	Vec2 diff = currentPos - _previousPos;
	_startPosition = diff + _startPosition;

	Vec2 newPos = _startPosition + Vec2(x,y);
	_target->setPosition(newPos);

	_previousPos = newPos;
	#else
	_target->setPosition(_startPosition + Vec2(x,y));
	#endif // !CC_ENABLE_STACKABLE_ACTIONS
	}
	}

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Sonar Systems admin

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There is a reason it’s done for you as realistic jumping isn’t easy but you may be able to replicate what you want with a mixture of normal actions with easing inside a sequence.

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pabitrapadhy

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Hi

Thank you for your help.
I got a forum reply from @mannewalis

greatly explained by him. Please do refer if anyone is seeking more knoledge. :)
here’s the link – http://discuss.cocos2d-x.org/t/explain-update-of-jumpby/20124/9?u=pabitrapadhy

also.. I want to thank SonarSystem for their quick and helpful response. :)

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Sonar Systems admin

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Your welcome :D

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