I want to be able to assign a shape a random direction to go in at a regular speed.
I tried assigning a random number to the x and y values of a translation but that caused the shape to sometimes move way too fast or just blip off the screen.
Is there a way to choose a random direction for a shape to move in without rotating the shape (at least as far as the user can tell)?
Also is there a way of re-genereating the random number when an event is called (ie: button click) which would allow a change in direction?
EDIT: Just checked. Using the rotate function with a random angle will shoot the square off in a random direction, but still is there a way to do this without altering the orientation of the shape?
Ok, so you want a shape to move in either the postive or negative x, y or z directions?
If you want this to be random then use the Random class. From this you can use Random.nextInt(1) which will either be 0 or 1, if the result is 0 then set the value to be -1.
The +1 or -1 is now used for your direction.
Now you know which way the object travels you can simply multiply this by the speed of your object
Here is some rough code
Random rand = new Random(); int direction = rand.nextInt(1);
if(direction == 0) direction = -1;
Shape theShape.position.x += direction * theShape.speed
This may not be how your interface is setup (such as theShape.position or theShape.speed) but the idea is the same
After reading this again I think you are trying to rotate your shape lol, rotation is not just adding to the x and y values. Do you use matrices in your application? If not your should use trig to figure out what the x and y values will be after a rotation of x degrees
Related
I'm trying to make a small circle move in another bigger circle as a ball moving in circle relative to Android phone tilting. I'm doing this in Godot but I think the principle is the same in all game engines probably. I make a scene in Godot and add two sprites as the two circles as the following picture. I get the accelerometer 3D vector, use x and y values and calculate the angle in x and y plate (relative to y axis i.e Vector2(0, 1) ) and rotate the mentioned scene to that degree using an animation, using this code
func _process(delta: float) -> void:
var vec3 = Input.get_accelerometer()
accelVec = Vector2(-stepify(vec3.x, 0.1), -stepify(vec3.y, 0.1))
var angle = accelVec.angle_to(Vector2(0, 1))
rotateTween.interpolate_property(self, "rotation", rotation, angle, 0.2,
Tween.TRANS_LINEAR)
rotateTween.start()
return
But the problem lies in here that when the x value of accelerometer 3D vector changes from a positive to negative value i.e when the ball is at top of the circle and is going to go to the other half of the circle, it actually moves from bottom of the circle to the desired point rather than from top of the circle.
I hope I explained the problem well, though I doubt it.
I added the Gif that shows actual test on an android phone here Testing in Android.
Any idea how to solve this problem?
Thanks in advance.
This is because Tween is interpolating linear values. It doesn't know it's working with angles, or that they should wrap around.
So when you're at -179 degrees and you tween to 179--a difference of 2 degrees--Tween just sees -179 -> 179 and goes through the whole circle.
You probably don't need a Tween here at all because _process() happens every frame.
I would like to detect collisions between shapes dynamically drawn on a canvas (SurfaceView) for an Android game.
I can easily use intersect method of Rect or RectF objects but the result is not very good (see picture below where I have a "false" detection).
I don't want to use Bitmap so it's impossible to use the "pixel perfect" method.
Do you know a way to do this for circle, rect, triangle and other basic shapes intersection ?
Thx for help ;)
For a good collision detection you have to create your own models behind. In those models you specify the conditions that two objects colide.
For example, a circle is described by the center position and by the radius. A square is described by the left down corner and by the edge length.
You don' t have to describe all possible poligons, you can use the so called bounding boxes, meaning that, for a complex random poligon you can use a square or whathever shape fits it best(also you can use multiple shapes for a single object).
After you have the objects in mind you compute the condition that each one of them will colide with all other shapes including itself.
In your example The sphere and the square colides if the distance between any corner of the square is greater than the circle's radius.
Here you can read more http://devmag.org.za/2009/04/13/basic-collision-detection-in-2d-part-1/
This problem can get very complex, keep it simple if you want something simple.
Here is a directly applicable method I use in my own game to detect circle and rectangle intersection. It takes the ball (which is a view in this case) and the rectangle (also a view) to be checked for collision with the ball as parameters. You can put the method in a Timer and set the interval you want the circle and rectangle to be checked for collision.
Here is the method:
public boolean intersects(BallView ball, Rectangle rect) {
boolean intersects = false;
if (ball.getX() + ball.getR() >= rect.getTheLeft() &&
ball.getX() - ball.getR() <= rect.getTheRight() &&
ball.getY() + ball.getR() <= rect.getTheBottom() &&
ball.getY() - ball.getR() >= rect.getTheTop())
{
intersects = true;
}
return intersects;
}
getR() gets the circle's radius
getX() gets the center of the circle's X position value
getTheLeft() gets the rectangle's left X value
getTheRight() gets the rectangle's right X value
getTheTop() gets the rectangle's top Y value
getTheBottom() gets the rectangle's bottom Y value
If you can't directly use this method in your code you can still conjecture the logic it entails to implement it where it would work for you. It detects all collisions without using pseudo-collision detection like a collision box for the circle.
Good luck! And if you have any questions feel free to ask, I'm here to help!
To know if a polygon in 2d is colliding with a circle, you can test, for each of its lines, where is the point on the line that is closest to the center of the circle (this might help).
Then, check if the point you found is between to two corners that make the line - that is, that the point is actually on the line, and not just on its continuation - and if the distance of that point to the center of the circle is smaller or equal to the radius of the circle. If both are true for any of the lines of the polygon, you have a collusion. You also have to check for the edge cases where the corners of the polygon might be in, or touching the circle.
For two circles, this is easier. Check the distance between the centers, and compare it to the sum of their radiuses. If the distance is smaller or equal to the sum, you have a collusion.
I will have an oval in the plane.The x and y co-ordinates of the center of oval and radius of the oval is known.Using a particle to move around the plane,have to verify whether the oval is circled(by moving the particle through all the sides of the oval).
How can I verify whether the oval is circled by the particle?
Consider centre of oval is (0, 0deg) in polar coordinates.
I am assuming your particle doesn't go inside the boundary of oval(from your words side of oval).
Minimize min and max with start position(atan(yParticle-yOvalCentre, xParticle-xOvalCentre)) of particles. Everytime particles goes towards min update min angle and similar for max. Once max - min > 360, you have completed the circle.
When you decided to start painting oval around circle, you created the starting vector from circle center to point (let's call it mouse point).
(mouseX-circleX, mouseY-circleY) = start vector
So, initial angle between current and starting vector will be 0 (until you move your mouse).
Mohit suggested you to check whether your current vector achieved some delta (359 deg is enough) between minimal and maximal angle value (angle can vary between -180 .. 180).
I'm not sure about his formula, though. I think it's better to find angle between starting vector (ax,ay) and current (bx,by) using the fact that
[a,b] = |a|*|b|*sin(alpha) = ax*by - ay*bx
(a,b) = |a|*|b|*cos(alpha) = ax*bx + ay*by
atan( [a,b] / (a,b) ) = atan(tan(alpha)) = alpha
So, calculate current angle on every mouse move and update min/max values, until max-min < 359
If you want to check it simultaneously for several circles, do it simultaneously for array of starting vectors and min/max values)
UPD I've noted big problem here, after painting 180 degrees around circle you'll achive -180 point immediately. So I think the best thing to do is to accumulate some summary value of signed delta angles between current and prevous "MouseMove" callback. So, when summary value will become 359 or -359 that mean you maked valid clock or counter-clockwise rotation.
Ohh.. damm Math !! once again stuck. It seems to be easy but i think its not that easy,
Problem Statement: I want to rotate the 3 fixed points which lies on a fixed circle.
1.when 1 point is selected remaining 2 points should be static mode and only selected point should move/rotate on circumference of circle.
2.And all 3 points are connected via 3 lines as shown in images..when we select a point and rotate it,connected lines also increase and decrease..
I already tried to solve this problem finding angle at each instant after touch.but its not quite working as per my need..
something like this
I hope the following explanation enable you to put the steps into your coding language.
Presumption is that the vertex to be moved has already selected and so the calculation of (xcnd,ycnd) as defined below is used to set the selected vertex of the triangle.
Let the constraining circle have centre at (cx,cy) and radius r.
Let the coordinates of where the screen is touched be (xtch,ytch)
Let the coordinates of where the screen is touched relative to the centre be (xrel,yrel)
then xrel = xtch - cx and yrel = ytch - cy
Let the coordinates of the point on the constraining circle when the screen is touched at (xtch,ytch) be (xcnd,ycnd).
xcndrel = xcnd - cx, and ycndrel = ycnd - cy give the coordinates on the constraining circle relative to its centre,
Note that
xrel and xcndrel will have the same signs (ie both positive or both negative)
and yrel and ycndrel will also have the same signs.
the function abs(x) = x if x>=0 and -x if x<0 should be available in whatever language you are using
the function sign(x) may or may not be available, sign(x) =1 if x>0 and -1 if x<0 and undefined for x=0
If not available then sign(x)=x/abs(x)
Check if xrel=0
if xrel=0 xcndrel=0, ycndrel=r*sign(yrel)
Otherwise work in first quadrant ie where x>0 and y>0 using abs(xrel) and abs(yrel)
find angle where screen is touched relative to centre of circle using
theta=arctan(abs(yrel)/abs(xrel))
find the coordinates (xcndrel, ycndrel) by using theta in the first quadrant and then placing in the correct quadrant using the signs of xrel and yrel
xcndrel = sign(xrel)*r*COS(theta)
ycndrel = sign(yrel)*r*SIN(theta)
Screen coordinates can now be found
xcnd = xcndrel +cx
ycnd = ycndrel + cy
I have a custom drawn rectangle which i want to move in a circular path based on touch events.
It follows the direction of the touch for clockwise or anticlockwise movement but basically move in circular motion, as if moving on the edge of the circle.
My current thought process is as follows:
Based on the users current and previous x,y i shall find the angle in degrees and then move this rectangle by the same angle by re-drawing in the new position, just making sure that it moves on the edge of a circle.
But this leads to some confusion on the following:
1. how do i decide whether angle movement is clockwise or anti-clockwise.
2. I am not being able to figure out the math for this properly.
Would this be the best approach or is there a better idea for doing this?
Also, if this is the best approach, could someone please tell me the formula for calculating the angle by which i should move it while taking care of the clocking and anticlockwise ?
could someone please help?
please let me know if any more details are required.
Thanks
Steps
Here are a few steps in order to move your rectangle along a circle's rim when the user taps and holds to the side of the circle:
1. Obtain direction desired.
2. Obtain angle from current x and y coordinates.
3. Add direction (+1 if counterclockwise, -1 if clockwise) to angle.
4. Calculate new x and y coordinates.
5. Update/display rectangle.
Details
1. In pseudocode, direction = sign(Rectangle1.x - UsersFingerPosition.x). Here sign is a function returning -1 if the number was negative, 0 if it is 0, and 1 if it is positive. Note that sign(0) will only result when the user is on the exact x and y of your rectangle's location. In that case, the rectangle would not move (which should be good). In Java, the sign function is Math.signum().
2. To obtain the current angle use the following java code:
double angle = Math.toDegrees(Math.atan2(Circle.y-Rectangle1.y, Rectangle1.x-Circle.x));
Note the order of Circle.y-Rectangle.y and Rectangle.x...Circle.x. This is a result of the coordinate (0, 0) being in the top left corner instead of the center of the screen.
3. Simple enough, just add direction to angle. If desired, do something like
angle += direction*2; //So it will move more quickly
4. To get the new x and y coordinates of your rectangle, use the trigonometric functions sine and cosine:
Rectangle1.x = Math.cos(Math.toRadians(angle))*Circle.radius + Circle.x - Rectangle1.width;
Rectangle1.y = Math.sin(Math.toRadians(angle))*Circle.radius + Circle.y - Rectangle1.height;
(where Circle.x and Circle.y are the coordinates of the center of your circle and Circle.radius is naturally it's radius).
5. This one you'll have to take care of (or have already) :)!
Hope this helps you!
Steps
Here are a few steps in order to move your rectangle along a circle's rim:
1. Obtain finger position/Check that it's still dragging the rectangle.
2. Obtain angle from current x and y coordinates.
3. Calculate new x and y coordinates.
4. Update/display rectangle.
Details
1. This one is probably specific to your code, however, make sure that when the user starts dragging the rectangle, you set a variable like rectangleDragging to true. Before you run the next steps (in the code), check that rectangleDragging == true. Set it to false once the user lets go.
2. To obtain the current angle use the following java code:
double angle = Math.toDegrees(Math.atan2(Circle.y-Finger.y, Finger.x-Circle.x));
Note the order of Circle.y-Finger.y and Finger.x...Circle.x. This is a result of the coordinate (0, 0) being in the top left corner instead of the center of the screen.
3. To get the new x and y coordinates of your rectangle, use the trigonometric functions sine and cosine:
Rectangle1.x = Math.cos(Math.toRadians(angle))*Circle.radius + Circle.x - Rectangle1.width;
Rectangle1.y = Math.sin(Math.toRadians(angle))*Circle.radius + Circle.y - Rectangle1.height;
(where Circle.x and Circle.y are the coordinates of the center of your circle and Circle.radius is naturally it's radius). Subtracting the width and height of the rectangle should center it on the circle's border instead of placing the left, upper corner on the circle.
4. This one you'll have to take care of (or have already) :)!
Hope this helps you!