Problem properly rotating Tank sprite

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Problem properly rotating Tank sprite

(7 posts) (4 voices)

Started 1 year ago by vivas
Latest reply from Benihana

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vivas
Member
Hi,

I am able to rotate and move the body of my tank (have not created the turret yet) using SneakyInput Joystick. The problem that I am having is that I want the front of the tank to face in the direction (degrees) of the joystick. Looking for ideas...

I think I need to rotate first, so that the sprite is facing the correct position ANd then actually move the sprite.

Right now it doesn't look very realistic - there is no way that a real tank could drive the way that it currently does in my game :-)

I have tried manipulating the anchor point but I'm still learning how to control sprite movement. Right now I am simply rotating the sprite like this:
```
if (leftJoystick.isActive) {
		tank.rotation = leftJoystick.degrees-90.0;
	}
```
The reason for the -90.0 is just to have the front of the tank pointing to 90 degrees when the joystick is pushed in that direction. I have looked for posts on the forum and was able to learn from this one: http://www.cocos2d-iphone.org/forum/topic/8156#post-47468

Any suggestions are appreciated.
Posted 1 year ago #
indy2005
Member

http://answers.yahoo.com/question/index?qid=20090221195007AA7bInc

perhaps use one tread or the other as the pivot point for the rotation as a real tank does ;-). If you want to turn right, set the anchor point to the right hand central side of the sprite, and the opposite for left...

Posted 1 year ago #
xcrunner509
Member

@vivas your timing for this question could not have been timed any better for me. I've been searching all weekend on how to use a sneakyjoystick to move a sprite/body. @ould you mind explaining to me how you are able to move the tank using a sneakyjoystick.

Posted 1 year ago #
vivas
Member
@indy2005 Thanks. I didn't know the treads operated like that. I'll try to reposition the anchor point accordingly. The main problem I seem to have is that the tank should:
- step #1 rotate then after the rotation is completed perform step # 2 which is to actually move in that direction.

Currently my tank looks like it is sliding on ice everywhere (ie. moving at a 45 degree angle side ways rather than the front of the tank 'leading' the way. This is how I am moving the tank now:
```
if (leftJoystick.isActive) {

		// Determine angle to face
		float angleDegrees = leftJoystick.degrees-90;
		float cocosAngle = -1 * angleDegrees;
		float rotateDuration = 0.4;
		[tank runAction:[CCSequence actions:
							[CCRotateTo actionWithDuration:rotateDuration angle:cocosAngle],
							nil]];
	}

	[self applyJoystick:leftJoystick toNode:tank forTimeDelta:delta];
```
// so what happens here, unfortunately, is the tank moves in the direction (degrees) of the joystick but it only rotates itself after the touch has ended, thus creating a 'sliding on ice' effect. I'm trying to get it to rotate first, then move.

@xcrunner509 Sure, I'm actually using the xCode project that comes with SneakyInput. Basically I added the following:

1. In HelloWorldScene.m in -(id)init I added this (I kept it simple and use the cocosGuy originally from the samples):
```
cocosGuy = [CCSprite spriteWithFile: @"tank.png"];
   cocosGuy.position = ccp( 200, 100 );
   [self addChild:cocosGuy];
```
2. In HelloWorldScene.m in -(void)tick:(float)delta I added this at the bottom of the method:
[self applyJoystick:leftJoystick toNode:cocosGuy forTimeDelta:delta];

That should create movement in the cocosGuy sprite when you move the left joystick. In order to rotate the sprite I followed the following thread exactly: http://www.cocos2d-iphone.org/forum/topic/8156#post-47468

That's all I have so far.
Posted 1 year ago #
xcrunner509
Member
Oh my god I accidentally had an extra line of code in the sprite part. I've got to remember to tell myself to look for simple mistakes. LOL thanks. Sorry but one more thing, did you figure out how to stop the sprite from going off the screen. Because I'm trying this
```
if(player.position.x > 320) player.position.x = 320;

	if(player.position.x < 0) player.position.x = 0;
```
That usually works for me, although it doesn't seem to be working for this situation, hmmmm....
Posted 1 year ago #
vivas
Member
Okay, In an attempt to control the 'rotate first, move second' logic I am using CCCallFuncND but getting a compile error. There are quite a few posts about CCCallFuncND in the forum but I haven't been able to resolve my problem. Here is the code:
```
id action = [CCCallFuncND actionWithTarget:self selector:@selector(moveTank:data:) data:delta];
		[tank runAction:[CCSequence actions:
							[CCRotateTo actionWithDuration:rotateDuration angle:cocosAngle],
							 action, nil]];
```
The moveTank method looks like this:
```
-(void)moveTank:(id)sender data:(float)pDelta{
	NSLog(@"moveTank method with pDelta: %f",pDelta);
	[self applyJoystick:leftJoystick toNode:tank forTimeDelta:pDelta];
}
```
The line that is giving me the 'incompatible type for argument 3 of 'actionWithTarget:selector:data.' is the line:
```
id action = [CCCallFuncND actionWithTarget:self selector:@selector(moveTank:data:) data:delta];
```
Any ideas?

@xcrunner509 glad you got it sorted out. I haven't gotten to the stage of keeping the tank on the screen just yet.
Posted 1 year ago #
Benihana
Member

The third argument is a pointer, but I'm betting you're trying to pass it a float. I can't tell for certain since you didn't include the delta init.

Posted 1 year ago #

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