Points and directionality

[Garry K]

A user clicks on 2 points and I create a door. Unfortunately if the user picks the right corner and drags to the left corner then my door gets created backwards. My problem is to detect which of the 2 points is the most left based on the current view. I have the bottom 2 points but I do not know which is right and which is left.

One strategy that I see is maybe I could use the camera's eye

Sketchup.active_model.active_view.camera.eye

I could create 2 vectors and then get the angle between the vectors.
But will this allow me to determine which is the most left?

[tt_su]

Would you not want to create the door in the direction the user picks the points?

Do you mean left/right in the viewport sense - or left/right in the sense of the 3d model space?

[Garry K]

@tt_su said:

Do you mean left/right in the viewport sense - or left/right in the sense of the 3d model space?

viewport sense - I think that's where the camera might help out.

[TIG]

I assume you are flattening the two points so pt2.z = pt1.z ?
And trapping for pt1.vector_to(pt2).parallel?(Z_AXIS)
And trapping for pt1==pt2 etc...

So now you have two coplanar points pt1 & pt2.

You always take the insertion-point as the left-hand-most-point and then the direction for the door from the vector of that insertion-point to the other-point.
eye = Sketchup.active_model.active_view.camera.eye
Then
ve1 = eye.vector_to(pt1) ve2 = eye.vector_to(pt2)
The check which point is "to the left using"
if ve1.parallel?(ve2) if ve2.length > ve1.length # nearest-point is insertion p1=pt1 p2=pt2 else p1=pt2 p2=pt1 end else # find ordering of points left/right cross = vec1.cross(ve2) if cross.z <= 0 p1=pt1 p2=pt2 elsif cross.z > 0 p1=pt2 p2=pt1 end end
Now use p1 & p2 for you insertion-point and direction calcs...
NOT pt1 & pt2 which might be swapped ??

[Garry K]

Thanks TIG - I'll chew on this for awhile and see where I get.
This line confuses me - I'm thinking a couple of typos??

cross = vec1.cross(ve2)[/ruby

did you mean

cross = ve1.cross(ve2) #ruby

[TIG]

cross = ve1.cross(ve2)

The other bit was a typo edit balls up !
I've removed it from my original text for the avoidance of confusion...

If you 'cross' two vectors you get a vector at right-angles to them.
It points 'up' [>0] or 'down' [<0] depending of the clockwise/ccw order of the vectors.
If you make the two points coplanar, with the same z, then it's either [0,0,-1] or [0,0,1] depending on the 'order' cw/ccw etc...

[Garry K]

TIG,

I didn't need the parallel code. I wanted to return the original pts and the flattened one

      pt1 = @ip1.position
      pt2 = @ip2.position

      p1 = Geom;;Point3d.new(pt1.x, pt1.y, [pt1.z, pt2.z].min)
      p2 = Geom;;Point3d.new(pt2.x, pt2.y, [pt1.z, pt2.z].min)

      eye = Sketchup.active_model.active_view.camera.eye

      ve1 = eye.vector_to(p1)
      ve2 = eye.vector_to(p2)

      return [pt2,pt1,p2] if( ve1.cross(ve2).z > 0 )

      [pt1,pt2,p1]

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