Delayed rotation

[_Tumppu_]

Hi there all

This is my first post and don't care about my spelling, English is not my native
language .

So I'm creating just a little tank game, everything is fine, tank is moving and cannon turning.

The problem is

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public void setDirection(float x, float y) { // parametres are mouse x,y          float rx = x - this.getX();    float ry = y - this.getY();    this.angle = (float)Math.atan2(ry, rx); // cannon angle }

This rotates the cannon okay, but, I would like to have some kind of delay to that turning (I mean, now
it's instant.
How is such a thing even possible? Somehow with delta time? I suck at math and physics sooo.

Well, if someone could help, I would really appreciate that!

Thanks in advance

edit. I try to explain better...

The cannon is now facing direction x,y
When I move the mouse, the facing direction changes of course to nx,ny.
I want it to be so that cannon slowly rotates to the new facing direction...

[Tjstretchalot]

Note I am not talking about experience here - have yet to succesfully build a game that lets you change angles =(

However, I do know a little bit about interpolation and extrapolation, which you probably need to former here if my knowledge is correct, or a form of it at least.

Save those variables as currentX, currentY and have it move some percent or absolute amount max at a time toward the current x/y and you have done it. Note that if this is an FPS of some sort or requires 'twitch' responses, this should be configurable, because it will give the user a different response then what he does, which will annoy them if it's twitch.

Here's some code

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protected static final float MAX_X_CHANGE = 10; // Random number protected static final float MAX_Y_CHANGE = 10; // will need testing protected float currentDesiredX; protected float currentDesiredY; protected float actualX; protected float actualY; protected void interpolateDirection() {   float diffX = currentDesiredX - actualX;   float diffY = currentDesiredY - actualY;   if(Math.abs(diffX) <= MAX_X_CHANGE) {     actualX = currentDesiredX;   }else {     actualX += Math.signum(diffX) * MAX_X_CHANGE;   }     if(Math.abs(diffY) <= MAX_Y_CHANGE) {     actualY = currentDesiredY;   }else {     actualY += Math.signum(diffY) * MAX_Y_CHANGE;   } }

EDIT - noticed it's just rotation, in which you can just modify the code appropriately. The variable names can be improved =P

[_Tumppu_]

Well thanks , I will take a look at it

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[_Tumppu_]

Ugh, dunno how to implement this....

[RobinB]

Haha

Well you have this.angle.
You could make another variable this.currentangle

then use something like this:

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float diff = this.angle - this.currentangle; if(diff < 0){ diff += (float)Math.PI * 2; } if(diff < Math.PI){     this.currentangle += 0.01f; }else{     this.currentangle -= 0.01f; }

You check the diffrence between the current and the destination angle.
If its close to the right, move right, else move left.

I always mess up + and - so you might need to switch the variables

[_Tumppu_]

Haha

Well you have this.angle.
You could make another variable this.currentangle

then use something like this:

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float diff = this.angle - this.currentangle; if(diff < 0){ diff += (float)Math.PI * 2; } if(diff < Math.PI){     this.currentangle += 0.01f; }else{     this.currentangle -= 0.01f; }

You check the diffrence between the current and the destination angle.
If its close to the right, move right, else move left.

I always mess up + and - so you might need to switch the variables

Heh okay thx. That's seems easier

[_Tumppu_]

Haha

Well you have this.angle.
You could make another variable this.currentangle

then use something like this:

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float diff = this.angle - this.currentangle; if(diff < 0){ diff += (float)Math.PI * 2; } if(diff < Math.PI){     this.currentangle += 0.01f; }else{     this.currentangle -= 0.01f; }

You check the diffrence between the current and the destination angle.
If its close to the right, move right, else move left.

I always mess up + and - so you might need to switch the variables

Thanks dude! That works veeery nicely!

[RobinB]

No problem, i remember i have had this problem once to.
The only problem you could have is; the cannon will be switching between 2 values all the time, with a greater movement rate you can spot this better.
Its easy to fix this problem anyway, didnt want to type to many code

[_Tumppu_]

Yeh, I noticed that little bug . Gonna try and fix it by myself . Thank you very much again