Thread: Drawing lines using angles in Java HELP

Hi All,

Im making a clock in java and i need help drawing the minutes and hours hand. I have done some maths and came up with the following formula

The formula i am using above is x = a + rCos(t)
y = b + rSin(t)
where (x,y) are the points on the circle i am trying to find and (a,b) is the centre of the circle. t is the angle between the x-axis and the line joining (a,b) and (x,y)

My clock is drawing perfectly, only it is 90degrees clockwise, so 12.00 looks like 15.00.
Ive tried to add/subtract degrees to the formula but its not working.

ive only shown the problematic code above, i can show the rest if needed.

Thanks you very much for looking at this,

Shady

I'd suggest throwing together an SSCCE that we can play with. I'm not sure I quite understand all the magic numbers in your code. Also note that the Math class has handy methods for converting between radians and degrees that might clear up some confusion.

Depending on how you're doing it, 6:00 shouldn't be 180 degrees, it's 90 degrees. You're assuming that straight up (12:00) is 0 degrees, but I believe that 0 degrees is heading straight to the right, 90 degrees is going down, 180 is to the left, and 270 is up (12:00). I could be wrong, but it would explain your problem.

Originally Posted by KevinWorkman

Depending on how you're doing it, 6:00 shouldn't be 180 degrees, it's 90 degrees. You're assuming that straight up (12:00) is 0 degrees, but I believe that 0 degrees is heading straight to the right, 90 degrees is going down, 180 is to the left, and 270 is up (12:00). I could be wrong, but it would explain your problem.

Thats one posibility i considered, i tried to add 90degrees to my values but it still doesnt point up
i.e.

But what this does is make 9:00 the new 12:00.
I try 90-h, h-90 etc no matter what values i put in it still does not point up.

Well, you're adding 90 to the hours and minutes and not an angle, which doesn't really make sense to me.

Originally Posted by KevinWorkman

Well, you're adding 90 to the hours and minutes and not an angle, which doesn't really make sense to me.

Oh. How would you suggest i do it then?

Btw i have updated the code, more viewer friendly now: