Problem with face.normal directions...help!

[renderiza]

In the graph below I can work out if a face is normal is facing on the direction specified in the first four examples. But I don't know how to evaluate if a face normal is facing giving the directions specified in the last four graph examples. Any help will be Appreciated!

If my problem is not clear please let me know I will try to explain it better...cheers!

[renderiza]

I think this might be it...Sorry not very good at math

Top Right = f1nx > 0 and f1ny > 0

Top Left = f1nx < 0 and f1ny > 0

Button Right = f1nx > 0 and f1ny < 0

Button Left = f1nx < 0 and f1ny < 0

[Chris Fullmer]

I'm not quite sure I understand, but I think I might have something helpful.

Find the dot product of the face's normal and the x_axis. If its a positive number, then the face normal is in the positive x range. Do the same for the y and z (if you need z). Try this code snippet, it will tell you if the face normal is pointing in a positive or negative x,y,z direction. Or it will tell you if the face normal is perpendicular to the model x,y, or z axis.

face=Sketchup.active_model.selection[0]
norm = face.normal
dot_products = {}
dot_products["x"] = norm.dot(X_AXIS)
dot_products["y"] = norm.dot(Y_AXIS)
dot_products["z"] = norm.dot(Z_AXIS)

dot_products.each do |key, value|

case 
  when value < 0
    puts "#{key} direction is a negative direction"
  when value == 0 
    puts "#{key} direction is perpendicular to the #{key} axis"
  when value > 0
    puts "#{key} direction is a positive direction"
 end
end

[renderiza]

Thanks Chris Fullmer your example does the job as well.

Here is another example that will select faces that are pointing to the top right...

model = Sketchup.active_model
sel = model.selection
ents = model.active_entities
faces = ents.grep(Sketchup;;Face)

faces.each do |face|
	f1nx = face.normal.x
	f1ny = face.normal.y
	
	#Face looking top right 
	if f1nx > 0 and f1ny > 0 
		sel.add face
	end
end

[tt_su]

That image in the OP isn't loading for me...

[Rich O Brien]

now?

[Chris Fullmer]

nope, not yet. It never showed for me either, I had to click on it to follow the link.

[TIG]

No.
The image links aren't working...

Above is http://s11.postimg.org/z4m5fepiq/question.jpg NOT these...
http://s11.postimg.org/jj4tvgdki/question.jpg ]
http://s11.postimg.org/ohsc9zhdd/question.jpg

[Rich O Brien]

I see it. NA NA NA-NA NA

[TIG]

Back to the question...
NorthEast Quadrant: normal.y>0 normal.x>0
SouthEast Quadrant: normal.y<0 normal.x>0
SouthWest Quadrant: normal.y<0 normal.x<0
NorthWest Quadrant: normal.y>0 normal.x<0

As you said:
Due North: normal.y==1 normal.x==0
Due East: normal.y==0 normal.x==1
Due South: normal.y==-1 normal.x==0
Due West: normal.y==0 normal.x==-1

Exactly Vertical: normal.z==0
Upwards Facing: normal.z>0
Downwards Facing: normal.z<0
Exactly Up: normal.z==1
Exactly Down: normal.z==-1