[Bf-python] Most efficient way to copy faces

[Toni Alatalo]

Toni Alatalo kirjoitti:
>> Well, is there a more efficient way to create the big list than 
>> iterating over all potato.faces checking iteratively their verts if they are the same 
>>     
> also a list comprehension might serve well there,
> f = [f for f in mesh.faces if inside(x, f)] #or something like that
> don't know about the efficiency but i suspect it's good for the case 
>   

looked a bit into the performance and reportedly it is good - with list 
comprehensions the iteration is done in c, without returning to the py 
interpreter in every place.there's an article referring to the docs and 
with a similar example, finding neighbours of every vertex, 
http://techorama.comyr.com/tag/list-comprehension/

i do recall Campbell reporting that a straight for loop in py can be 
more efficient if you are just doing something for a collection of 
things, as the list comprehension has the overhead of making the list, 
but in your case when you exactly making a list it should be good.

>> Lynx
>>     
> ~Toni
>   

again.

>>> mesh.faces.extend().  Not sure how you handle UVs and the like though,
>>> it's kindof a pain, I think.
>>>
>>> Joe
>>>
>>> On Sun, May 24, 2009 at 12:41 PM,  <lynx.abraxas at freenet.de> wrote:
>>>       
>>>> Hello,
>>>>
>>>>
>>>>
>>>> Next question: What is the most efficient way to copy faces from 
>>>> another mesh?
>>>> I have now the verts that lie within an ellipsoid and now I'd like 
>>>> to copy the
>>>> faces that belong to these verts. I'm doing it currently like this:
>>>>
>>>>
>>>>
>>>> if len(vin.verts) > 2: # we need at least one face => three verts 
>>>> minimum
>>>>      #find inside faces in potato to copy
>>>>      for i in range(0, len(potmesh.faces)): #check all potato faces
>>>>         nvi= 0
>>>>         f= []
>>>>         for j in range(0, len(potmesh.faces[i].verts)): #if all 
>>>> verts of a face
>>>>            for k in vin.verts: #are in the list of the inside verts
>>>>               if k.co == potmesh.faces[i].verts[j].co:
>>>>               #if k in potmesh.faces[i].verts:#this does not work! 
>>>> why?
>>>>                  nvi+= 1
>>>>                  f.append(k)#create face with vin.verts indices!
>>>>         if nvi == len(potmesh.faces[i].verts): #if all verts of a 
>>>> potato face are in the inside verts list
>>>>            vin.faces.extend(f) #add it to the list of insede faces
>>>>         elif nvi > len(potmesh.faces[i].verts):
>>>>            print "Potato mesh contains double verts!"
>>>>            #vin.faces.extend(f) #only possible for 2 to 4 verts!
>>>>         #else:
>>>>         #   print "Face not completly inside ellipsoid."
>>>>
>>>>
>>>> This  is  taking  a  long time for my big "potato" (3 million verts, 
>>>> 1 million
>>>> faces). Is there a better way to do this?
>>>>
>>>> Many thanks for any help or hints
>>>> Lynx
>>>>
>>>>
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