draw arc

Manufraktur

Hi there,
I am not sure if this is the correct category to post this.
I am trying to draw an arc and I cannot find any example or explanation concerning this. In the documentation it says:
arc(center, radius, startAngle, endAngle, clockwise)
but it didn't work.
Assuming the center has two coordinates, I tried:
arc((10, 10), 10, 20, 25, True) and
arc(10, 10, 10, 20, 25, True), both didn't give a result.

There were a few discussions and examples about arcTo(), but that didn't help me as I am trying something like this:

Did anybody try something similar before?
Thank you in advance for your help,
Petra

gferreira

hello @Manufraktur,

here is a simple example using arc() to create a slice of pie:

from math import sin, cos, radians, pi

x0, y0 = 500, 500 # center point (A)
radius = 350
angleStart = 10
angleTotal = 55

# draw circle with radius
fill(0, 1, 0)
oval(x0 - radius, y0 - radius, radius * 2, radius * 2)

# calculate point (B) from angle and radius
angleStartRadians = pi / 2 + radians(angleStart - 90)
x1 = x0 + radius * cos(angleStartRadians)
y1 = y0 + radius * sin(angleStartRadians)

# draw pie slice using arc
B = BezierPath()
B.moveTo((x0, y0))
B.lineTo((x1, y1))
B.arc((x0, y0), radius, angleStart, angleStart + angleTotal, False)
B.closePath()
fill(1, 0, 0)
drawPath(B)

# draw points labels
fill(0, 0, 1)
fontSize(120)
text('A', (x0, y0))
text('B', (x1, y1))

arc() is a bit tricky to use because point B and angleStart need to be kept in synch manually.

notice that, in this script, B is defined with distance & angle in relation to A.

if you prefer to define B by x/y position, as in your example, you’ll need to calculate the angle and distance of B in relation to A:

from math import hypot, atan2, degrees

x0, y0 = 500, 500 # A
x1, y1 = 872, 600 # B 
angleTotal = 55

radius = hypot(x1 - x0, y1 - y0)
angleRadians = atan2(y1 - y0, x1 - x0)
angleStart = degrees(angleRadians)

# ...same as previous example...

hope this makes sense! cheers

Manufraktur

Dear @gferreira,
thanks for your quick reply. It seems like this could solve my problem. I will give it a try tomorrow and let you know.

But thank you already so much for your help!
Petra

Manufraktur

Dear @gferreira,
I tried to use your suggestion it in my exercise and it worked fine. Thank you so much for your help! Amazing.
Thank you and kind regards,
Petra