[Podunk]

I'm trying to figure out a way to calculate an angle.

The angle is derived from 2 sets 2 dimensional vector coordinates



I want to draw a line from point A to point B


example:
[point A]
(X,Y)
|
|
|
[point B]
(X,Y)


the angle origin is [horizontal left]:


<---- 0 degrees
^
|
| 90 degrees

---> 180 degrees

|
| 270 degrees
V

In the example the angle would be 270 degrees.


My second problem is a programming one.

I'm working with a 2D plane, and I have 32 objects which move freely around on the plane.

The program has a "ticker" that fires about 12 times a second. - I'll use this to move the objects around each tick.
I need to figure out how to smoothly move all of the objects to their destinations each "tick".

Each object has individual destinations and speeds of travel which makes this fuzzy

[TheNewt]

so create arrays like this
objLoc[32][2]
objVel[32][2]

The first array will store the object's location and the second will store how quickly the objects move in what direction.

so object 1's X location would be objLoc[0][0] and the same object's Y location is objLoc[0][1].

I'd probably write a loop that would just tell each object to update

public static void main(String[] args) {
	loop();
}

loop() {
	while(true) {
		//You could write something here to change the object's velocity.
		update();
	}
}

update() {
	for(int i = 0; i<32; i++) {
		objLoc[i][0] += objVel[i][0];
		objLoc[i][1] += objVel[i][1];
	}
}

That'd be one way to

[_Master_]

And now for the bomb: COLLISIONS.

[TheNewt]

LOL

[Podunk]

Thanks Mystic, but that would only work if the ticker was exactly 12 times a second. The ticker is variable and could fire 1-12 times a second so I have to use time to move the objects.

[OneEyed]

First Problem:

Length = sqrt( x*x + y*y )
Normal = ( x/length , y/length )
DOT Product = (x1*x2 + y1*y2) //Use normalized points

Angle Between 2 Vectors = acos( point1 DOT point2 )

acos can be arccos, cosarc, icos, invcos, cosinv, whatever the language your using made it.

In PAWN code.

new Float:a[2] = { 1.0, 5.0 };
new Float:b[2] = { -3.0, 2.0 };

new Float:lenA = floatsqrt( (a[0]*a[0]) + (a[1]*a[1]) );
new Float:lenB = floatsqrt( (b[0]*b[0]) + (b[1]*b[1]) );

a[0] /= lenA; 
a[1] /= lenA;
b[0] /= lenB;
b[1] /= lenB;

new Float:dotprod = ( (a[0]*b[0]) + (a[1]*b[1]) );

//If you want radians change "degrees" to "radians". 
new Float:angle = floatacos( dotprod, degrees);

Second Problem:
To move gradually along a line, you'll need to adjust your direction (IE. Velocity) to size up to the distance to be traveled in one second. Then to make your object gradually move across the direction. Divide it up by how many ticks you run a second. The higher # of ticks the smoother it'll look.

Pseudo Code Example:

//Runs 12 times a second.
GameFrame()
{
    float rate = 12.0;
    Vector velocity;
    velocity.x = 3.0;
    velocity.y = 5.0;

    ObjectOrigin.x += velocity.x / rate;
    ObjectOrigin.y += velocity.y / rate;
}

That there will move your object's origin up 3 units and across 5 units every second.

[_Master_]

Unless your objects are insolid, you seem to be missing the point. Making an object "move" in real-phisics is the easy part. How to avoid objects is hell, and I'm fairly sure a little AI is added into it.

As a side-note: check "line" algorithms (from C/C++/JAVA/etc.) for incremental x, y calculations. You can assume x,y to be the next step and the increment as velocity. WAY faster to compute.

[Podunk]

very nice info thanks a lot guys!

[Podunk]

Originally Posted by OneEyed First Problem: Length = sqrt( x*x + y*y ) Normal = ( x/length , y/length ) DOT Product = (x1*x2 + y1*y2) //Use normalized points Angle Between 2 Vectors = acos( point1 DOT point2 )

Say I wanted to move from

1,1
to
13,15

Length = sqrt(1*1+13*15) = 14
Normal1 = (1*14,1*14) = (14,14)
Normal2 = (13*14,15*14) = (182,210)
DOT Product = (1*13+1*15) = 28
angle = acos((14,14)28(182,210)) = what?

I totally get lost around Normal1.