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