Array of unique points?

[thomthom]

When you have an array of arbitrary points - and you want to ensure that array only contains unique points, how do you filter them out?

points.uniq! doesn't seem to work.

Example:

` point1 = Geom::Point3d.new 1,1,1

Point3d(1, 1, 1)
point2 = Geom::Point3d.new 10,10,10
Point3d(10, 10, 10)
point3 = Geom::Point3d.new 10,10,10
Point3d(10, 10, 10)
a = [point1, point2, point3]
[Point3d(1, 1, 1), Point3d(10, 10, 10), Point3d(10, 10, 10)]
a.uniq
[Point3d(1, 1, 1), Point3d(10, 10, 10), Point3d(10, 10, 10)]`

[Chris Fullmer]

Any chance you are getting the points from an array of vertices? Vertices will respond to the uniq(!) methods. I can't think of any time that I actually sorted by Point3d objects. And I tihnk it was because I found it easier to use vertices, which has always worked out ok for what I was writing.

Chris

[thomthom]

No, not vertices. computed intersections.

[thomthom]

atm I got this code:

def self.uniq_points(points)
  old_points = points.clone
  new_points = []
  until old_points.empty?
    point = old_points.shift
    point_exists = false
    new_points.each { |p|
      if p == point
        point_exists = true
        break
      end
    }
    new_points << point unless point_exists
  end
  return new_points
end

but I was wondering if there was a better method....

[Chris Fullmer]

Yeah, as I was thinking - each Point3d object is its own object, and therefore different, even though they might share the same coordinates in space.

You need to compare them as strings I suppose, since I see no quicker comparison method(?). Try this line:

` a = [point1.inspect, point2.inspect, point3.inspect]

a.uniq`

That should work, I don't know how slow it will be if its over zillions of points though,

Chris

[thomthom]

no, not string. you can compare two points - point1 == point2 if return true if they are the same point, withing some tolerance SU has set. But it seems that array.uniq doesn't do this type of comparison...

[TIG]

Point3d's will be uniq!'d if they have the same ID BUT NOT if they have just the same XYZ values [they aren't really equal are they?], but we can write a simple def to sort it out...

def unique(pointsIN = [])
  return pointsIN if pointsIN.to_a[0].class != Geom;;Point3d
  # we'll only process an array of Point3d's ?
  points_a = []; pointsIN.to_a.compact.each{|p| points_a << p.to_a}; pointsa.uniq!
  # we compact to remove any 'nil' entries ?
  pointsOUT = []; points_a.each{|p| pointsOUT << Geom.Point3d.new(p.x, p.y, p.z)}
  return pointsOUT
end#def
# Assuming a list [array] of Point3d's that might contain duplicates called 'points' then...
points = unique points
# will give us a list [array] of unique Point3d's called 'points'...

[TIG]

Alternatively, following TT's point1 == point2 idea

def unique(pointsIN = [])
  pointsOUT=[]
  pointsIN.to_a.each{|p|
    duplicated = false
    pointsOUT.each{|po|
      if po == p
        duplicated = true
        break
      end#if
    }
    pointsOUT << p if not duplicated
  }
  return pointsOUT
end#def
points = points unique

Which keeps the Point3d's IDs unchanged...

[MartinRinehart]

@thomthom said:

But it seems that array.uniq doesn't do this type of comparison...

Have you tried just adding them to a set?

[thomthom]

I was pretty sure I'd tried that! But clearly I haven't!

` point1 = Geom::Point3d.new 1,1,1

Point3d(1, 1, 1)
point2 = Geom::Point3d.new 10,10,10
Point3d(10, 10, 10)
point3 = Geom::Point3d.new 10,10,10
Point3d(10, 10, 10)
s = Set.new
#Set:0xbd7da68
s.insert(point1)
#Set:0xbd7da68
s.insert(point2)
#Set:0xbd7da68
s.insert(point3)
#Set:0xbd7da68
s.to_a
[Point3d(1, 1, 1), Point3d(10, 10, 10)]`

Very interesting that it evaluates differently. It compares the values, not the objects.
Exactly the kind of solution I was hoping for.