Move movieClip towards rotation angle

[XaeroDegreaz]

Hi, I'm trying to move a movieClip based on it's _rotation property.

I have a little triangle that could represent a spaceship perhaps.

If the triangle is facing up (0 degrees) I want it to move straight up when I press the UP key. If it is facing 45 degrees, I want it to move forward in that direction.

Could someone help me with the math involved in moving a movieClip towards its rotation angle?

Thanks in advance.

[Durnus]

Okay, I'll give this a shot. Pretty simple, I just get my directions messed up a lot

Someone can fix this if they want to, but this is basically it:

//Let's assume your movieclip is called MC, and you changed _rotation to change your object's angle.

//Say, this var represents distance in pixels.
var SPEED = 5;

//It would be one pair of these two lines, I'm not sure which:

MC._x += Math.cos(MC._rotation)*SPEED;
MC._y += Math.sin(MC._rotation)*SPEED;
//or
MC._x += Math.cos(MC._rotation/180*Math.PI)*SPEED;
MC._y += Math.sin(MC._rotation/180*Math.PI)*SPEED;

But, just so you know:
Up is not zero degrees. Right is. I think down is 90, and it goes around that way, but I'm not sure.

I hope my code helped, it probably won't work, but at least it's something.

[XaeroDegreaz]

Yeah, I kinda have something like that.

I can tell it's trying to work, because the triangle does change directions based on angle. However, it doesn't go the correct way

[ASWC]

speedx =Math.sin(this._rotation*(Math.PI/180))*2;
speedy = Math.cos(this._rotation*(Math.PI/180))*2*-1;


this._x+=speedx*speed;
this._y+=speedy*speed;

Use what you want as a "speed" variable.

[XaeroDegreaz]

You the man brotha. That's exactly what I needed!

Thanks a lot

[ASWC]

Hey Durnus, just so you know the _rotation in Flash output values from -180 to 180, instead of from 0 to 360, so when writing function for that you have to translate everything into values you can use.

[Durnus]

I didn't know that, but cos(180+90) would output the same out cos(-90), correct? (Assuming we are using degree mode.) So therefore, how did you know I didn't know it was from -180 to 180? :P

You did catch the - for the y. I didn't get that, I always debug the signs after I write the whole thing. I never get stuff right the first time.

[ASWC]

I just do a lot of stuff like that in Flash. I knew you didn't know since your code couldn't work but was close enough.
In fact if you add 180 then you have a 0 to 360.

[XaeroDegreaz]

Now I need to come up with something clean for acceleration and deceleration.

-_- Man, I hate math.

Most I do in math is count grams and ounces.

[ASWC]

By the way I can tell you are doing a Asteroid clone, am I right?