Actually, it turns out I was not looking for Ed Catmull's papers, but Jos Stam's papers:
http://www.dgp.toronto.edu/people/stam/reality/Research/pub.html My mistake. Thanks, -- Raul On Mon, Apr 24, 2017 at 4:15 PM, R.E. Boss <[email protected]> wrote: > 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 ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
