How to subtract Point3D.Z value with a variable

[bakbek]

seems simple but i can't make this thing work

this is form Robin Hills HeightTool.rb

def onLButtonUp(flags, x, y, view) #called when left mouse button released
txt='Height: '+@pt[2].to_s
model=Sketchup.active_model
e=model.entities
t=e.add_text txt,@pt,@vec
end

what i want to do is make this tool work relative to a set zero level... not the files axis zero. i get the user set level with the same method as in the drop ruby script so now i have a @@level=The user set value

but performing
txt='Height: '+(@pt[2]-@@level).to_s

doesn't show the right value
@@level.to_s alone works well but the subtraction doesn't

what am i doing wrong here

[todd burch]

@bakbek said:

txt='Height: '+(@pt[2]-@@level).to_s

doesn't show the right value

@@level.to_s alone works well but the subtraction doesn't

what am i doing wrong here

What value is displayed?

What is @@level prior to the subtract? What is its class?
What is @pt[2] prior to the subtract? What is its class?
What is the class after you do the subtract?

[todd burch]

As we can see from this prior reference:

t=e.add_text txt,@pt,@vec

@pt is a Point3D. Therefore, @pt[2] would be the z value.

Personally, I would have coded

@pt.z

but to each his own.

[AlexMozg]

I think that all is far simpler...

txt='Height; '+(@pt[2].z - @@level.to_l).to_s
...
or
For example;
@@level = 100.mm
txt='Height; '+(@pt[2].z - @@level).to_s

[bakbek]

Hi Todd & Alex, thanks for your assistance.

I've attached a screen capture for you to see what I'm trying to achieve here... it's not working yet.

using the context menu when clicking on a surface i can assign the surface height to the @@level variable, it is suppose to be a number or length class as far as i can say. when i assign it directly to txt i get proper values... it is the math with the @pt (point3d class) that gets odd values as you can see in the image

the proper height should have been 120cm at the note but it is 47.244094488189

i guess i either mix up classes or units or something else i don't know about

---

[a4chitect]

try converting your results to the metric system, you are probably getting sketchup internal imperial units.

[bakbek]

how to? this is what i can't seem to get right

[GreyHead]

Google says 120 centimeters = 47.2440945 inches

Bob