Oups! you're right. that's the problem!
I am trying to make a dragon curve.

Well, i tried but it seems that doesn't work...
And i don't understand why not.
Here is my complete script (with nbit correction)

lg = 1.m
nbit = 5
point1 = [0,0,0]
point2 = [lg,0,0]
point3 = [lg,lg,0]
norm = [0,0,1]
group0 = Sketchup.active_model.entities.add_group
line = group0.entities.add_line point1,point2
line = group0.entities.add_line point2,point3
pivotpt = point3

nbit.times{
  t = Geom;;Transformation.rotation(pivotpt, norm, 90.degrees)
  group1 = group0.copy
  group1.transform!(t)
  group0 = group0.parent.entities.add_group([group0, group1])
  pivotpt.transform!(t)
}

Maybe i may transform the coordinates system instead. Or do you know another trick like using an indexed variable name for t?

As said in the subject, i would like to know if it's possible to reset a transformation in loop.
example :

x=0
while x < nbit
  t = Geom;;Transformation.rotation(pivotpt, norm, 90.degrees)
  group1 = group0.copy
  group1.transform!(t)
  group0 = group0.parent.entities.add_group([group0, group1])
  pivotpt.transform!(t)
  x += 1
end

I found the correction myself.
And I use:

group1.transform!(t0)

instead of:

group1.transformation = t0

But if someone can explain to me why this works with transform! but not with .transformation
i would be thankful.

Hello, i would like to script a dragon curve so i first wrote this :

` mod = Sketchup.active_model # Open model
ent = mod.entities # All entities in model
sel = mod.selection # Current selection
point1 = [0,0,0]
point2 = [1,0,0]
point3 = [1,1,0]
group0 = Sketchup.active_model.entities.add_group
line = group0.entities.add_line point1,point2
line = group0.entities.add_line point2,point3

t0 = Geom::Transformation.rotation( [1, 1, 0], [0,0,1], 90.degrees)
group1 = group0.copy
group1.transformation = t0

group2=group0.parent.entities.add_group([group0, group1])

t1 = Geom::Transformation.rotation( [2, 0, 0], [0,0,1], 90.degrees)
group3 = group2.copy
group3.transformation = t1

group4=group2.parent.entities.add_group([group2, group3])

t2 = Geom::Transformation.rotation( [2,-2,0], [0,0,1], 90.degrees)
group5 = group4.copy
group5.transformation = t2`

But the thrird rotation gave me unexepected result. It seems to be a rotation and a translation.
Why?