Which are the papers you want and cannot find?
R.E. Boss > -----Original Message----- > From: Chat [mailto:[email protected]] On Behalf Of Raul > Miller > Sent: maandag 24 april 2017 18:51 > To: Chat forum <[email protected]> > Subject: [Jchat] catmull clark > > The catmull-clark surface subdivision algorithm is an issue I have been > neglecting for a few years: > > avg=: +/ % # > havePoints=: e."1/~ i.@# > > catmullclark=:3 :0 > 'mesh points'=. y > face_point=. avg"2 mesh{points > point_face=. |: mesh havePoints points > avg_face_points=. point_face avg@#"1 2 face_point > edges=. ~.,/ meshEdges=. mesh /:~@,"+1|."1 mesh > edge_face=. *./"2 edges e."0 1/ mesh > edge_center=. avg"2 edges{points > edge_point=. (0.5*edge_center) + 0.25 * edge_face +/ .* face_point > point_edge=. |: edges havePoints points > avg_mid_edges=. point_edge avg@#"1 2 edge_center > n=. +/"1 point_edge > 'm3 m2 m1'=. (2,1,:n-3)%"1 n > new_coords=. (m1 * points) + (m2 * avg_face_points) + (m3 * > avg_mid_edges) > pts=. face_point,edge_point,new_coords > c0=. (#edge_point)+ e0=. #face_point > msh=. (,c0+mesh),.(,e0+edges i. > meshEdges),.((#i.)~/$mesh),.,e0+_1|."1 edges i. meshEdges > msh;pts > ) > > Example use: subdividing a cube: > > points=: _1+2*#:i.8 > mesh=: 1 A."1 I.(,1-|.)8&$@#&0 1">4 2 1 > > catmullclark mesh;points > > This all is straight out of the rosettacode implementation > https://rosettacode.org/wiki/Catmull–Clark_subdivision_surface#J > > Now..., reading Ed Catmull's papers (which used to be easy to find > downloadable copies of - catmull had a few websites which are probably still > up, but no longer seem to be findable using search. Now I am getting 404 > results from some of the more plausible seeming leads that I can find using > search, other than http://dl.acm.org/citation.cfm?id=907242), the underlying > concept has to do with a useful analogy between eigenvectors, b-splines and > geometric normals. Sadly, though, I was never able to reproduce his results > following that line of thought - which probably means I lack some relevant > math background. > > So, my question here, is: what kinds of classes am I likely to need to take, > to > reproduce Catmull's thesis work? > > I understand that this is an ill-formed question, so maybe a fallback question > would be: where would I find out about math / computer science topics at > University of Utah professors and curriculum in the early '70s? Who would I > talk to, I suppose might ask? > > Thanks, > > -- > Raul > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
