Fruit Ninja Swipe

Question

I now have nearly completed a Cut The Rope type game. I need only a swipe mechanic to cut the rope, both the logic and the visual effect. Suggestions would be most welcome.

I only need a concept for what to do in this situation. I tried doing it in two ways already, but I don't satisfied with it.

1. I used a particle system, but I get random points on the screen. So the effect does not convey its meaning. I have following link in which I have implemented a line drawing algorithm with particle system. https://stackoverflow.com/questions/10702328/drawing-line-effect-on-touch-like-fruit-ninja-or-veggie-samurai-in-and-engine

2. I used a simple and single sprite, and perform scale, transformation, and rotation but I don't get desire effect that looks perfect for rope cutting.

I have knowledge about CCBlade class in cocos2d but I found it difficult to convert it into Java.

Any help is greatly appreciated.

Answer 1

Here in the following link I post my code that I used to create ninja swipe effect.

http://www.andengine.org/forums/gles1/draw-gl10-gl-triangle-strip-fruit-ninja-swipe-effect-t7257.html

This link contains whole discussion about this topic but at last I post my code and image so any user can immediately create this effect.

Answer 2

For the cutting-line drawing, I could think of a simple logic that tracks user input with a short interval and draws lines from the tracked points like this ->

If the user is cutting ( touching the screen / mouse down + move ) you could check the cursor position point in a desired interval, and draw a line from the last point to the current point until user stops cutting ( mouse up ).

While cutting ( mouse move ), vou could apply a simple particle system where the emitter is following the input position. play with some values in the particle system to make sure that the spawning point is just in place, by applying a force ( gravity ) you can make the particles fall down. Play with the lifetime value.

To animate the "rope" that is been cut, you could define a "force" value to the rope. By detecting if the rope and the cutting-line are overlapping, you can define the cutting point, where the animation starts, the upper end of the rope is just pushed up a little bit ( defined by the force of the rope ) and the lower end is just falling down.

I think you'll find some good techniques on "chain animation" or something. This would be a little bit of work to the physics engine.

Well, this is just my theory. I have never done this kind of game before.

I hope this idea helps you find your solution.

Answer 3

I might do it this way... I wrote a game that had a throwing mechanic using the mouse, and its similar. I'm also assuming you are using touch primarily.

Get the time when your finger touches the screen. On the touch move callback, see how much time has passed and how far you have gone from the original point. You can get the distance using Pythagoreaus' theorem (sqrt(x^2 + y^2)). Set a threshold for the swipe to trigger. If the distance traveled / time taken >= threshold, trigger the swipe functionality. It's a basic software accelerometer, but should be effective.

I might also have a stop time condition because you don't want your slash to go on forever.