This question already has answers here:
Calculating the position of points in a circle
(13 answers)
Closed 9 years ago.
I want to place some menu icons on a circle so that it almost looks like a clock. Depending on the amount of icons, the space between them may vary. Whats the best way to put each of these icons in the form of a circle?
Mathematics.
If you know how many items you have then you can find the angle between them because you know there are 360 degrees (2pi radians) in a circle. Choose a start point and then use
x = centerX + r * cos(angle)
y = centerY + r * sin(angle)
Using the center point of the circle, the radius and the angle (in radians), increasing the angle for each item.
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Althougth i have read many articles on internet regarding it, i m unable to solve my issue.
There is a 2D plan where x, y is the top left point of the screen.
I have a point from which i know the position x, y, the direction (0 to 360 degrees) and a speed (in pixel per step ).
According to what i have read, if i want to calculate the next position of the point after one step i use the following code:
self.px.X := round(self.px.X + self.speed * cos(direction));
self.px.Y := round(self.px.Y + Self.speed * sin(direction));
For testing purpose i use a speed value of 10 and a direction of 90.
Normally, the point should move horizontally (or even vertically would be a progress), but it is moving in a diagonal movement, not even something like 45°.
Anyone knows what i'm doing wrong ?
As said by Andreas Rejbrand (but i don't know how to turn a comment into an answer, sorry Andreas), the solution was to use radians number by simply calling degToRad function:
self.px.X := round(self.px.X + self.speed * cos(DegToRad(direction)));
self.px.Y := round(self.px.Y + Self.speed * sin(DegToRad(direction)));
I am trying to achieve a view in which Images will placed on edge of circle.I tried to make it with CAShapeLayer and added UIImageViews but I want to create it dynamically. Any help will be appreciated.I am adding one image for example.
I would suggest you to refer this answer given by #rob_mayoff
You should create a circular bezier path with the image you want to display.Please not that this method only works if you want to have same image distributed evenly on the circle.If you want to have different image distributed evenly on circle, then you should do put more effort .
You can try in two ways:
Draw every circular bezier path by calculating their centers . And arrange them in a circular manner. You should do a little math. Please note that you have the center point (x,y) for the main circle, and place the sub circles around the center point (x,y) in such a way that distance from each sub circle center to main circle center should be same. To get the exact coordinates of lines which divide the circle , please refer to the answer. Once you get the exact coordinate, you can place the subcircle at these positions.
I will try to give a rough idea about doing this:
Consider you have a main circle whose center is at (x0,y0). And you wish to place images on this circle by dividing the circle into 'n' parts. so that you can place 'n' number of imageViews on this main circle. The 'n' parts are denoted by green lines in the below picture.
The angle between each of the green lines is 360deg/n
No we need the end point of the each green line. Which can be obtained from:
sub.x = x0 + r * cos(angle);
sub.y = y0 + r * sin(angle);
where r is the radius of main circle.
This is for one sub circle. In yoour case you have 'n' number of sub circles, so let's do a loop to get all sub circle centerpoints:
for(i = 1 to n)
{
angle = i * (360/n);
sub.x = x0 + r * cos(angle);
sub.y = y0 + r * sin(angle);
}
Now you can draw a circular bezier path at each of the 'n' sub (x,y) points
using the addArcWithCenter:center where center would be the calculated sub (x,y)
I think 1 is again the best way if you want to do everything dynamically.
This question already has answers here:
Value of sine 180 is coming out as 1.22465e-16
(4 answers)
Closed 7 years ago.
I'm beginner developer for iOS. I use some online tutorials to learn Swift and now I'm trying to develop my own calculator. There is task to down "sin" and "cos" buttons by my own, which would return sine or cosine function for entered value.
Of course, there is sin() and cos() functions in the Swift, but I've found, that it returns values in radians, not degrees. I did search and found code, smth like that
func sind(degrees: Double) -> Double {
return sin(degrees * M_PI / 180.0)
}
which I implemented in my code. Now everything looks fine, buttons returns correct values. But there is sine of 180 degrees is 0 and when I enter 180 in my calculator and press "sin" button it returns another value. Same for cosine of 90 degrees, should be 0 but returns another value.
Could you please explain how possible to fix it? Full code at github: https://github.com/senator14/firstcalculator.git
The problem with sine and cosine functions is that M_PI is an irrational number is approximately defined as 3.14159265358979323846264338327950288 which means that it has some error.
One possible solutions to your problem is having the ranges of input form -PI/2 to PI/2. This reduces the error of approximation. The following changes your range to -90 to 90 degrees.
sin(((fmod($0, 360) > 270 ? fmod($0, 360) - 270 : ((fmod($0, 360) > 90) ? 180 - fmod($0, 360) : fmod($0, 360))) * M_PI / 180.00)) }
Reference from here
I have a physics body, and I want it to move forward in the direction that it is facing. I'm only thirteen which I hope explains why I'm so bad at trigonometry. Can anyone tell me how to do this in Corona?
I'm gonna assume you want to push your object with a force. Either way we'll need to get an x and y component of the direction your body is facing. Here's how to get the x and y from the rotation angle:
-- body is your physics body
local angle = math.rad(body.rotation) -- we need angle in radians
local xComp = math.cos(angle) -- the x component
local yComp = -math.sin(angle) -- the y component is negative because
-- "up" the screen is negative
(note: if this doesn't give the facing direction, you may need to add 90, 180, or 270 degrees to your angle, for example: math.rad(body.rotation+90) )
The above code will give you the x and y components of the unit vector in the direction of the rotation. You'll probably also need some multiplier to get the magnitude of force you want.
local forceMag = 0.5 -- change this value to apply more or less force
-- now apply the force
body:applyLinearImpulse(forceMag*xComp, forceMag*yComp, body.x, body.y)
Here's where I got the math: http://www.mathopenref.com/trigprobslantangle.html. Using a unit vector simplifies the math because the hypotenuse is always 1
How about making your own character moving towards an angle before using the confusing physics?
angle = math.rad(Insert the angle you want here)
character.x = character.x - math.sin(angle)
character.y = character.y + math.cos(angle)
Er. You don't need Trigonometry just to move the object.
Add
object:translate(distanceToMoveInXAxis,distanceToMoveInYAxis)
Or if you want to perform a transition,
transition.to(object,{x=object.x + distanceToMoveInXAxis,y=object.y + distanceToMoveInYAxis})
How to get Random Geo-points[ lat/long in decimal], placed anywhere inside a 100 meter radius circle? The center of the circle is another reference GeoPoint.
Is there any Function/Formulae that implements this?
Basically I am reading the GPS input of my android device and need to generate random Geo-Points around the device [In a circle of radius 100 meters centered at my device].
Please note : There are no Geo-Points pre-stored in Database. I need to create all the Geo-points on the fly as mentioned above.
I just wrote a a Ruby method which extends Random to provide this.
Caveat: The points all lay within a box, not a circle.
class Random
def location(lat, lng, max_dist_meters)
This is called with Random.new.location(mid_lat, mid_lng, dist). It will return a point which is probably within max_dist_meters of a the mid point.
max_radius = Math.sqrt((max_dist_meters ** 2) / 2.0)
Without adjusting to max_radius we'd get points inside a square outside the circle (i.e. in the corners), where the distance would be greater than max_dist_meters. This constrains us to a square inside the circle which is probably more what you want.
lat_offset = rand(10 ** (Math.log10(max_radius / 1.11)-5))
lng_offset = rand(10 ** (Math.log10(max_radius / 1.11)-5))
The 1.11 and 5 come from here.
lat += [1,-1].sample * lat_offset
lng += [1,-1].sample * lng_offset
lat = [[-90, lat].max, 90].min
lng = [[-180, lng].max, 180].min
We should probably wrap around here instead of just clamping the value, fixes welcome.
[lat, lng]
end
end
Comments / clean up welcome!
Sample output here which you can see nicely if you paste the lat/lngs here.
Pick random points on a square (i.e. pairs of uniform random numbers), then discard any that don't lie within a circle inscribed in that square. Given (x,y) pairs, a point is within your circle if:
(x - c_x)^2 + (y - c_y)^2 < r,
where (c_x, c_y) is the centre of your circle and r is its radius.
Start here: Generate a random point within a circle (uniformly). Then figure out how to center that circle at the reference lat/long. Then figure out how to map the randomly generated points to lat/long values. Hint: you want to add the individual components (say, x and y on your circle) to the circle's center.