Via a tech-artists.org tweet, I came across some MAXScript for randomly selecting a specified percentage of mesh elements (for example, give me a random selection that includes 35% of all vertices).
I converted it to Python in Softimage. Note that I don’t really shuffle a collection: you can’t set items in a collection, so there’s no way to swap items. Instead, I put the collection in a list and shuffle the list.
si = Application log = si.LogMessage sisel = si.Selection #http://creativescratchpad.blogspot.ca/2011/06/select-random-elements-by-percentage.html import random # # Return a list that includes a randomly selected # percentage of the items in a collection # def get_random_percentage( collection, percentage ): v = [x for x in collection] # random shuffle for i in range( len(v) ): j = random.randint( i, len(v)-1 ) v[i], v[j] = v[j], v[i] # select by percentage step = 100/percentage w =  for i in xrange( 0, len(v), step ): w.append( v[i] ) # print len(w) # print (percentage/100.0) * len(v) return w Application.SelectObj("torus", "", True) # Select a random 50% of the vertices x = get_random_percentage( sisel(0).ActivePrimitive.Geometry.Vertices, 50 ) si.SelectObj(x) print sisel(0).SubComponent.ComponentCollection.Count # Suppose you had 2000 cubes. # Select a random 25% of those 2000... Application.SelectObj("cube*", "", True) x = get_random_percentage( sisel, 25 ) si.SelectObj(x)
I learned a couple of things about MAXScript:
- MAXScript arrays are 1-based
- In the MaxScript docs, there aren’t any function/method reference pages. You have to go to a “value” page (eg Number Values) and there you’ll find all the methods. That’s fine once you know, but it was confusing at first when I didn’t see anything in the TOC for Functions or Methods.