Talk:Catmull–Clark subdivision surface

What's the input for the function? Example input/output?

typical 3D datas are formated like this: an array of vertex points first (x,y,z) 3D coordinates with type (float, float, float), they are indexed from 0 to (n - 1), then a list (or array) of faces, a triangle face is specified with 3 ints, and a quad face with 4 ints, the ints are the indexes in the first array. This data model is most often used because vertices belongs to several faces, so there are no duplication of the coordinates with this model.

here are below a typical input and output for the Catmull-Clark subdivision surface algorythm, the input is a simple cube:

input_points = [
  (-1.0,  1.0,  1.0);
  (-1.0, -1.0,  1.0);
  ( 1.0, -1.0,  1.0);
  ( 1.0,  1.0,  1.0);
  ( 1.0, -1.0, -1.0);
  ( 1.0,  1.0, -1.0);
  (-1.0, -1.0, -1.0);
  (-1.0,  1.0, -1.0);
]

input_faces = [
  (0, 1, 2, 3);
  (3, 2, 4, 5);
  (5, 4, 6, 7);
  (7, 0, 3, 5);
  (7, 6, 1, 0);
  (6, 1, 2, 4);
]

# below after one iteration:

output_points = [
  (-0.555556,  0.555556,  0.555556);
  (-0.555556, -0.555556,  0.555556);
  ( 0.555556, -0.555556,  0.555556);
  ( 0.555556,  0.555556,  0.555556);
  ( 0.555556, -0.555556, -0.555556);
  ( 0.555556,  0.555556, -0.555556);
  (-0.555556, -0.555556, -0.555556);
  (-0.555556,  0.555556, -0.555556);
  ( 0.000000,  0.000000,  1.000000);
  (-0.666667,  0.000000,  0.666667);
  ( 0.000000, -0.666667,  0.666667);
  ( 0.666667,  0.000000,  0.666667);
  ( 0.000000,  0.666667,  0.666667);
  ( 1.000000,  0.000000,  0.000000);
  ( 0.666667, -0.666667,  0.000000);
  ( 0.666667,  0.000000, -0.666667);
  ( 0.666667,  0.666667,  0.000000);
  ( 0.000000,  0.000000, -1.000000);
  ( 0.000000, -0.666667, -0.666667);
  (-0.666667,  0.000000, -0.666667);
  ( 0.000000,  0.666667, -0.666667);
  ( 0.000000,  1.000000,  0.000000);
  (-0.666667,  0.666667,  0.000000);
  (-1.000000,  0.000000,  0.000000);
  (-0.666667, -0.666667,  0.000000);
  ( 0.000000, -1.000000,  0.000000);
]

output_faces = [
  ( 0,  9,  8, 12);
  ( 1, 10,  8,  9);
  ( 2, 11,  8, 10);
  ( 3, 12,  8, 11);
  ( 3, 11, 13, 16);
  ( 2, 14, 13, 11);
  ( 4, 15, 13, 14);
  ( 5, 16, 13, 15);
  ( 5, 15, 17, 20);
  ( 4, 18, 17, 15);
  ( 6, 19, 17, 18);
  ( 7, 20, 17, 19);
  ( 7, 22, 21, 20);
  ( 0, 12, 21, 22);
  ( 3, 16, 21, 12);
  ( 5, 20, 21, 16);
  ( 7, 19, 23, 22);
  ( 6, 24, 23, 19);
  ( 1,  9, 23, 24);
  ( 0, 22, 23,  9);
  ( 6, 24, 25, 18);
  ( 1, 10, 25, 24);
  ( 2, 14, 25, 10);
  ( 4, 18, 25, 14);
]