Can you please explain why norm of Line is 90 CCW from it vector?

[redexp]

Hello, I'm trying to figure out why Flatten.Line has norm vector which is 90 CCW from original vector? It was surprise for me that to build vertical line code should be NOT

new Line(new Point(10, 10), new Vector(0, 1))

it should be

new Line(new Point(10, 10), new Vector(-1, 0))

instead. In docs it says just norm - normal vector to a line, nothing about 90 CCW.

Thanks great lib.

[alexbol99]

Hello, @redexp Sergii

I don't understand what do you mean by "original vector", but both options are valid.
Both options give same vertical line that passes through the point (10,10)
What kind of problem you have with this definition?

Best regards,
Alex

[redexp]

@alexbol99 as for me, first one should be vertical line, but it is horizontal line. To build vertical line I need to pass horizontal vector, why?

[redexp]

This is vertical vector new Vector(0, 1) right? and with it we should build vertical line like this new Line(new Point(10, 10), new Vector(0, 1)), right?

[alexbol99]

My answer was quick and incomplete.
Constructing of the line with normal vector (n) and point (pt0) means definition of the line equation in vector form :

 n * p = 0

where
norm - normal (ortogonal) vector to a line
p = pt - pt0 - vector from a point p0 that line passes through to an arbitrary point on a line
and '*'' is a scalar product

So, in order to construct vertical line you need to create horizontal vector, and both

new Line(new Point(10, 10), new Vector(-1, 0))

and

new Line(new Point(10, 10), new Vector(1, 0))

are constructors for same vertical line.

You also have an option to construct line that pass through two points, like this:

new Line(new Point(10, 10), new Point(10,20))

[redexp]

Thank you for explanation