I am working in cocos2dx game developing and working on circle gesture detection . I would like to ask how can I find angle between two points.How can i find angle between two points A and B.my ccTouchesMoved event as follows.
void HelloWorld::ccTouchesMoved(CCSet *pTouches, CCEvent *pEvent)
{
CCLog("Touches moved");
CCTouch *touch = (CCTouch*)pTouches->anyObject();
location = touch->getLocation();
location=CCDirector::sharedDirector()->convertToGL(location);
prevLocation=CCDirector::sharedDirector()->convertToGL(touch->getPreviousLocationInView());
deltax=prevLocation.x-location.x;//difference of x
deltay=prevLocation.y-location.x;//difference of y
angle=??// i want this angle using deltax and deltay
}
You need to include math header and you can calculate angle in degree using formula:
angle = atan2 (deltay, deltax) * (180 / PI);
Related
Hello I'm trying to make a billiards game using libgdx. I'm using 3d models for the balls and an Orthographic Camera to view them. I am having trouble getting them to roll correctly after rolling on a different axis. Here is a clip of what they look like when they're rolling.
As you can see they appear to be rotating as if they were on their starting axis. Is there any way to rotate it so that it looks like it's actually rolling. I am also not very familiar with transformation matrices or quaternions so im not too sure where to go.
Edit: Updated for clarity
Here is the code I use to update the rotation
public boolean update() {
if (!visible) {
return false;
}
Vector2 vBall = ballBody.getLinearVelocity();
float vAngle = ballBody.getAngularVelocity();
isMoving = true;
float x = ballBody.getPosition().x * SCALE;
float y = ballBody.getPosition().y * SCALE;
Vector2 axisInPlane = new Vector2(y - center.y, x - center.x).rotateRad(Math.PI/2f);
Vector3 axis3D = new Vector3(axisInPlane.x,axisInPlane.y,0f);
ball3D.transform.rotate(axis, (float) Math.toDegrees(dist / RADIUS_PX));
ball3D.transform.setTranslation(mapX(x), mapY(y), 0);
Just to be sure, center is an arbitrary fixed point where there is no rotation and all rotations are derived from this distance/angle as the ball has no slippage.
So you can directly get the axis with
Vector2 axisInPlane = new Vector2(y - center.y, x - center.x).rotateRad(Math.PI/2f);
Vector3 axis3D = new Vector3(axisInPlane.x,axisInPlane.y,0f);
Also Math.toDegree takes radians as an argument, not a float, so dist/RADIUS_PX will be off, you have to supply as a fraction of 2PI (360 degs in radians). Also this should be the circumference of the ball not the radius. I don't know what class ball3D is but I would check that ball3D.transform.rotate does take degrees as an argument and if it does replace that line with
float rotateRadians =(float) Math.toDegrees((dist/CIRCUMFERENCE_PX)*Math.PI*2f);
ball3D.transform.rotate(axis, rotateRadians );
I'm making a top down shooter game. I've got my character moving. All I want to do next is make a bullet shoot from the center of my character to the direction my cursor is at. How would i go about doing this?
I'm really struggling to think of the code i need to make this work.
This will involve simple vector math. There are tons of resources online about this. Here's the basic gist:
1) First, calculate the angle (in radians) between your character and your target (in this case the mouse location). You can use Math.atan2() to perform this calculation.
var angle:Number = Math.atan2(mouseY - playerY, mouseX - playerX);
2) Next, use that angle to create a vector (x,y delta) which represents the direction of travel for your bullet. You use Math.cos() and Math.sin() to compute the x and y value:
var speed:Number = 5;
var vector:Point = new Point(Math.cos(angle) * speed, Math.sin(angle) * speed);
3) Now you can update the bullets position each frame by that vector:
bullet.x += vector.x;
bullet.y += vector.y;
4) And if you want to make your bullet sprite point in the direction of travel, convert that angle to degrees and set the bullet sprite's rotation:
var degrees:Number = angle * (180 / Math.PI);
bullet.rotation = degrees;
Note that for the purpose of the math here, 0 degrees is considered to be right-facing along the x-axis, not up-facing like you might naturally think of 0 degrees (at least I do). What this means is your sprites unrotated orientation should be facing right-ward.
Hello all,
I'm creating a game where some particles are created after a collision between two objects. The particles are then given a random x and y velocity and they shoot out in every direction. I've been trying to alter the way the particles shoot out to resemble Figure 1, where the particles shoot out at a randoom angle between 330 to 30 and 150 to 210 (I wrote the angles in degrees rather than radians for an ease in understanding). The red areas in Figure 1 are where the particles shouldn't shoot out and the blue is where they should. I have not been able to achieve the desired effect however. I was wondering if anyone could assist with a link to helpful reading or an example in code. I have been searching google but cannot find a decent example.
Figure 1
Notes:
- The angles are written in degrees but will need to be changed to radians because Flash uses radians, a simple conversion (Math.pi/180) added to the code should suffice.
- Figure 1 resembles the Cartesian Coordinate system but the y axis is inverted in Flash's coordinate system.
- I would post the code that I have tried but it is so far from what is desired that it would not help.
var speed:Number = minSpeed + Math.random() * (maxSpeed - minSpeed);
var angle:Number = Math.random() * 120 - 30;
if (angle > 30) angle += 120;
angle *= Math.PI/180;
var speedX = Math.cos(angle) * speed;
var speedY = Math.sin(angle) * speed;
I am creating a game in which I draw a series of polygons by creating points around a radius of a cricle.
Later on I rotate the shapes and I need to calculate the new location (X,Y) of the points based on the rotation. I have the Old XY of each point, the XY of the center of the shape, radius of shape and the rotation.
Have a look at my diagram of the problem.
It should be possible to use matrix transformations for this, but you can also do it manually:
http://www.siggraph.org/education/materials/HyperGraph/modeling/mod_tran/2drota.htm
So essentially;
newX = initialX * Math.cos(angle) - initialY * Math.sin(angle);
newY = initialY * Math.cos(angle) + initialX * Math.sin(angle);
//Angle is in radians btw
This assumes that the initialX/Y is relative to the center of rotation, so you would have to subtract the center point before starting, and then add it again after the calculation to place it correctly.
Hope this helps!
For each point do:
alpha = arctan2(x, y)
len = sqrt(x^2 + y^2)
newX = len * cos(alpha + rotation)
newy = len * sin(alpha + rotation)
Original [x,y] and new [newX,newY] coordinates are both relative to the center of your rotation. If your original [x,y] is absolut, you have to calculate relative first:
x = xAbs - xCenter
y = yAbs - yCenter
Make sure your arctan2 function provides a result of PI/2 or -PI/2 if x=0. Primitive arctan functions do not allow x=0.
I'm programming a flash game, I made an array of points (x and y positions) that some movieclips must follow. Those movieclips have a certain speed (they make steps of 5 pixels for now). When I want to move them horizontally or vertically, everything's fine, I have to add or remove 5 pixels of those clips' x or y. But sometimes they have to move diagonally and now that's complicated.
What I'm doing:
var angle:Number = Math.atan2(nextPoint.y - this.y, nextPoint.x - this.x) * 180 / Math.PI;
var xstep:Number = Math.cos(angle) * this.speed;
var ystep:Number = Math.sqrt(Math.pow(this.speed, 2) - Math.pow(xstep, 2));
this.x += xstep;
this.y += ystep;
It's only a fraction of the code, but I think it's all you need.
Basically, this makes my movieclip do a little step (of this.speed (currently set to 5) pixels).
If the current point and the next point have the same y position, it works fine. When they don't, it doesn't work. The angle is right at first but it slowly decreases (while it should stay the same). I don't know if it's the angle that isn't computed the right way or if it's the x and y steps, but it's one of those, I'm sure.
Try this instead:
var angle:Number = Math.atan2(nextPoint.y - this.y, nextPoint.x - this.x);
var xstep:Number = Math.cos(angle) * this.speed;
var ystep:Number = Math.sin(angle) * this.speed;
Because cos operates on angles in radians, you don't need to convert to degrees. Computing the y component of an angle uses sin, so it should be similar to x. I'm not able to test this, but it's possible that ystep will be backwards and may need to be multiplied by -1.