Gui Arrow Guide.

#1 It all depends if you want to do it in 2D or 3D.

A quick way: You can (on server side), take the position of the player and position of the next checkpoint. Then you can compute the angle between the forward vector of your player and the vector form by the two previous position (used dot vector product with normalized vector and you will get the cos of the angle). It should work ok.

#2 Bit over my head that.. :+}
By forward vector do you mean the transform of the car?.
I have tried but couldn't get it to work correctly.
Maybe its becouse you don't mean the transform of the car?.
How do I get the forward vector of the car?.

#3 Ok, I see it now. Dough!.
%car.getForwardVector();
That would return the forward vector and would then work fine.
I have spent two days trying to get this to work and it would seem I was barking up the wrong tree with transform. The fromFwd is what got me thinking its was the transform that was needed. I guess you learn something new every day (Or two in my case :+} ).

#4 Almost forgot to say thankyou Frank Bignone, for writing the "FuelOMeter, SpeedOMeter like control" resource, updating the guimeterctrl and for helping with this problem.
Many thanks again.
:+}

#5 You're welcome.

#6 I have this sort of working with the following.

function getAngle(%itemPos, %playerFwd, %playerPos){
  %itemFwd = VectorSub(%playerPos, %itemPos);
  %myAngle = mRadToDeg(mAcos(VectorDot(VectorNormalize(%itemFwd), VectorNormalize(%playerFwd))));
}

Only problem is that when the car is pointing towards the object it returns 180 degrees and not 0. Also there is no -180 degrees.

What I need is when facing towards an object, it returns 0 degrees.
When turned to one side it returns 90 degrees.
When turned to the other side it returns -90 degrees.
I need this for every degree from -180 (Facing away) through to 0 (Facing towards) through to 180 (Facing away again).

Anyone got any idea where this is going wrong?.

#7 I have managed to get this working a lot better but its not totaly accurate.
I don't pretend to understand all the math and have done this by reading other posts and resources and with help form other people like Frank Bignone and my brother in law who has an eng background.

Here is the code to return the angle to an object. Again note that the angle returned is not totaly accurate. :+O

function getAngleFromVectors(%itemPos, %playerFwd, %playerPos){
	//Work out the forward vector between the two position vectors.
	%itemFwd = VectorSub(%playerPos, %itemPos);
	
	//Work out the angle the object is from the player fwd vector. This will always be an angle >= 0.
	%myAngle = mRadToDeg(mAcos(VectorDot(VectorNormalize(%itemFwd), VectorNormalize(%playerFwd))));
	//%myAngle is the oposite 180 of the angle we require. If %myAngle is 10 Degrees then its actualy 170 degrees. 20=160, 30=150, 40=140 etc.
	%myAngle = 180 - %myAngle;

	//Make the angle sloppy by 10 degree's, 5 either side of 0 to counter act the needle jumping when passing the object up close.
	%myAngle = %myAngle - 5;
	if (%myAngle < 0 ){
		%myAngle = 0;
	}
	
	//Work out the side the object is on from the players forward vector. + left or - Right.
	%crossProduct = VectorCross(VectorNormalize(%itemFwd), VectorNormalize(%playerFwd));
	%rotation = GetWord(%crossProduct, 2);
	if (%rotation < 0 ) {
		//Angle needs to be a negative angle of the same amount as its on the right.
		%myAngle = %myAngle - (%myAngle * 2);
	}
	
	//Return the angle.
	return %myAngle;
}

Example of how to use this function

%angleToObject = getAngleFromVectors(obj.position, localclientconnection.car.getForwardVector(), localclientconnection.car.position);

The angle returned in %angleToObject is the angle from the car's forward vector in + or - 0 to 180 degrees.
Degrees above 0 are to the left and degrees below 0 are to the Right.


If anyone can improve on this please post below.

Below are the problems the function has that seem to effect the accuracy of the angle returned.
The angle returned by the following line of code it the oposite of the 180 angle and I don't understand why.

%myAngle = mRadToDeg(mAcos(VectorDot(VectorNormalize(%itemFwd), VectorNormalize(%playerFwd))));

Because I couldn't fix the above problem, I worked with it and used the following code to reverse the andle.

%myAngle = 180 - %myAngle;

I have spent a long time trying to get this to work and this works well enough for now, but it would be great to get it to work with more accuracy.

#8 There are some screenshots on our forum if anyone is interested.
www.uklanparty.net/modules.php?name=Forums&file=viewtopic&t=545