appleGuy

02-04-2009, 03:50 PM

Hi,

im having a little trouble with movie the original vertex, based on the algorithm:

http://en.wikipedia.org/wiki/Catmull-Clark_subdivision_surface

Assuming I have a quad of: (-1, -1, -1), (1, -1, 1), (1, 1, -1), (-1, 1, -1)

Now say i want to re-position the top left vertex (-1, 1, -1)

**The centroid of the face is: (0.0, 0.0, -1.0)

**The Valence is 2

**The Average Of mid points connection vertex is: (-0.5, 0.5, -1.0)

If i plug those into the formula i get:

vp = (([0, 0, -1] + (2 * [-0.5, 0.5, -1.0]) + ((2-3) * [-1, 1, -1] ))) / 2

= ([0, 0, -1] + [-1, 1, -2] + [1, -1, 1]) / 2

= [0, 0, -2] / 2

= [0, 0, -1]

This is not the correct position for the original point however.

Please can someone tell me where im going wrong?

Thanks,

im having a little trouble with movie the original vertex, based on the algorithm:

http://en.wikipedia.org/wiki/Catmull-Clark_subdivision_surface

Assuming I have a quad of: (-1, -1, -1), (1, -1, 1), (1, 1, -1), (-1, 1, -1)

Now say i want to re-position the top left vertex (-1, 1, -1)

**The centroid of the face is: (0.0, 0.0, -1.0)

**The Valence is 2

**The Average Of mid points connection vertex is: (-0.5, 0.5, -1.0)

If i plug those into the formula i get:

vp = (([0, 0, -1] + (2 * [-0.5, 0.5, -1.0]) + ((2-3) * [-1, 1, -1] ))) / 2

= ([0, 0, -1] + [-1, 1, -2] + [1, -1, 1]) / 2

= [0, 0, -2] / 2

= [0, 0, -1]

This is not the correct position for the original point however.

Please can someone tell me where im going wrong?

Thanks,