[Req] Check for N-Gons

Khai

would it be possible to write a Ruby (or Tig, for you to add this to Manifold...!) that checks a mesh for N-Gons? (N-Gon face that is greater than 4 sides)

remus

Your wish is my command. Give me 5 mins...

Version 3:
works over the entire model (in groups and components), thanks to TIGs handy little snippet.
Adds all N-gons to a new selection
Tells you how many N-Gons there are in the model
Added a Tri check which can be accessed by typing tri_check() in to the ruby console

ngon_check.rb

remus

Here you go, copy and paste this in to jims/alexs web console and click run.

model = Sketchup.active_model
entities = model.entities
selection = model.selection

n = 0

entities.each{|e|
  if e.is_a? Sketchup;;Face
    if e.edges.length > 4
      n += 1
    end      
  end
}

if n > 0
  UI.messagebox("Contains N-Gons (Faces with >4 sides)")
else
  UI.messagebox("N-gon free!")
end

remus

...or just install this script as usual.

ngon_check.rb

Khai

thanks I owe you one

Khai

oops.... it's not working... everythings coming up as N-Gon free....

jeff hammond

khai, i'm pretty sure it's not looking inside groups/components otherwise it appears to be working.

Khai

aah explode it first... I tried with just groups and selecting the group... did'nt think to explode it first..

remus

Sorry i didnt reply, internet cut out.

As jeff pointed out its not gong through faces that are within groups/components for some reason. This version will go through all the faces in the current context, so a slight improvement but not much better. Not sure why it doesnt work on all the faces in the model straight off

ngon_check.rb

TIG

Remus
Your current script finds all faces in the the active_entities - those in the current 'edit' session.
Perhaps do that if selection.length==0, but do it on selection if >0 ?
You could also do it on entities which would be all faces in the base model.
To get absolutely all faces in the model and its definitions [components and groups] use


faces=[]
model=Sketchup.active_model
model.entities.each{|e|faces<< e if e.class==Sketchup;;Face}
model definitions.each{|d|d.entities.each{|e|faces<< e if e.class==Sketchup;;Face}}
### then test 'faces' array for 4-sidedness ones...

It depends which faces you want to list - i.e. all or all-active or all-selected ???

solo

Wondering out aloud.... so what then? you find the N-gons what do you do with them? divide them into triangles?

TIG

@solo said:

Wondering out aloud.... so what then? you find the N-gons what do you do with them? divide them into triangles?

My triangulateFaces or triangulateQuads already does that ?
I expect he wants to find un-triangulated faces > quads for some other esoteric processing .................

Khai

actually to divide them into Quads (preferred) or Tris - I use Sketchup as a modeler for other programs you see, they prefer no N-Gons... (Mainly poser content)

remus

TIG, i realise the current script only works in the current context (in a group etc.), it was on purpose as i thought it was more useful than only being able to check the faces in the highest context.

On another note, does entities not include faces, edges etc. that are within components? If so that would explain why khai was having trouble with it...

TIG

@remus said:

TIG, i realise the current script only works in the current context (in a group etc.), it was on purpose as i thought it was more useful than only being able to check the faces in the highest context.

On another note, does entities not include faces, edges etc. that are within components? If so that would explain why khai was having trouble with it...

active_entities is everything in the current edit session - i.e. in the model or a group or component being edited.
entities is everything in the model - as in model.entities but stops short of nested stuff so it lists all geometry, groups, instances etc.
You also use entities for other containers like groups or component_definitions - e.g. group.entities and definition.entities. again these stop short of listing nested stuff.
To find ALL entities you need to do my trick of iterating through the model.definitions and going through the entities of each definition...
Remember too that if you are changing entities always use an array as in ents.to_a - changing entities as you ' each' loop through them leads to unpredictable results as the entities list constantly changes and so it becomes confused...

remus

Cheers for the explanation

Khai

presto reserectus!

http://forums.sketchucation.com/viewtopic.php?f=169&t=24681&p=247955#p247955

I'm wondering if this can be expanded now to highlight the Ngons? we're finding with Sculptis it rejects any faces with more than 4 faces....

remus

Try this in the webconsole. To be honest your probably better off using TIGs triangulate faces ruby, though...

model = Sketchup.active_model
entities = model.active_entities
selection = model.selection

n = 0

entities.each{|e|
  if e.is_a? Sketchup;;Face
    if e.edges.length > 4
      n += 1
      selection.add(e)
    end      
  end
}

if n > 0
  UI.messagebox("Contains N-Gons (Faces with >4 sides)")
else
  UI.messagebox("N-gon free!")
end

Khai

webconsole?

and I explained back in this thread.. I can't tri the mesh. I'm moving from here (I love the modeler!) to app that don't like things being totally tri's... so that ruby's no good to me.

remus

Webconsole is a handy little ruby that lets you run bits of ruby in SU without having to package it as a separate file. You can find it here: http://sketchuptips.blogspot.com/2007/08/plugin-webconsolerb.html

Just install it as usual, open SU, hit the appropriate menu item, copy and paste the code in and click run.

I'll get going on a normal version, but no promises. Its been a while since ive written a ruby.