Hello, I am making a 3d engine and I absolutely need an “atan2” function. Those anyone know how to make a workaround? (I would like that it returns the answer in degres.)

Discuss below.

arctan2 x: () y: () :: operators reporter

([atan v] of ((x) / (y)))

should work.
EDIT: Never mind, I forgot about negative arctangents.

TheCreatorOfUnTV wrote:

([atan v] of ((x) / (y)))

should work.

Except you need logic to handle different quadrants, and it's a bit of a headache. I think it's a reasonable workaround, though, given the advanced nature of trigonometry

if <(x) = [0]> then
if <(y) > [0]> then
set [atan2 v] to [90]
else
set [atan2 v] to [-90]
end
else
if <(x) > [0]> then
set [atan2 v] to ([atan v] of ((y) / (x)))
else
set [atan2 v] to (([atan v] of ((y) / (x))) + (180))
end
end

To convert the result to a Scratch direction where 0 is up and 90 is right:

point in direction ((90) - (atan2))

It works! In about 10 minutes I finished my 3D engine and it is now available here .

Maximouse wrote:

if <(x) = [0]> then
if <(y) > [0]> then
set [atan2 v] to [90]
else
set [atan2 v] to [-90]
end
else
if <(x) > [0]> then
set [atan2 v] to ([atan v] of ((y) / (x)))
else
set [atan2 v] to (([atan v] of ((y) / (x))) + (180))
end
end

To convert the result to a Scratch direction where 0 is up and 90 is right:

point in direction ((90) - (atan2))

set [atan2 v] to (([atan v] of ((y) / (x))) + ((180) * <(x) < [0]>))

This also works. There is no need for special checks when one of the axes are 0 using it, though if you want Scratch's bearings, subtract it from 90 like how Maximouse shows.

awesome-llama wrote:

This also works. There is no need for special checks when one of the axes are 0 using it, though if you want Scratch's bearings, subtract it from 90 like how Maximouse shows.

Aha… intuitively (and if you're just doing math instead of IEEE 754), you need the x=0 check to avoid zero division (it's in Wikipedia's atan2 definition). But atan is smart enough to know what to do with Infinity and -Infinity.

True. I am using that one for my black hole simulation game

awesome-llama wrote:

set [atan2 v] to (([atan v] of ((y) / (x))) + ((180) * <(x) < [0]>))

This also works. There is no need for special checks when one of the axes are 0 using it, though if you want Scratch's bearings, subtract it from 90 like how Maximouse shows.