Delaunay triangulation implementation in matlab -

-

hello it`s first post here. want write matlab script delaunay triangulation. here script:

clear all;clc %% delaunay x=[ 160.1671 366.9226 430.7894 540.1208 660.2771 508.7287 252.1787]; y=[ 223.9615 259.5000 120.5769 245.5000 283.1923 472.7308 469.5000];  % x=x'; y=y';  %orginal plot dd=delaunay(x,y); dt=trirep(dd,x,y); triplot(dt); z=[x.^2+y.^2] i=1:length(x); ptk=[i' x y] %% main loop l=0; i=1:length(x)-2 j=1+i:length(x)     k=1+i:length(x)         if (j ~= k)             l=l+1;             xn = (y(j)-y(i))*(z(k)-z(i)) - (y(k)-y(i))*(z(j)-z(i));             yn = (x(k)-x(i))*(z(j)-z(i)) - (x(j)-x(i))*(z(k)-z(i));             zn = (x(j)-x(i))*(y(k)-y(i)) - (x(k)-x(i))*(y(j)-y(i));                 if (zn < 0)                     border=zn;                         m=1:length(x)                             border = (border) & ...                                 ((x(m)-x(i))*xn +...                                 (y(m)-y(i))*yn +...                                 (z(m)-z(i))*zn <= 0);                             if (border)                              ii(m)=[i];                             jj(m)=[j];                             kk(m)=[k];                             end                         end                 end         end     end end end wart=[ii' jj' kk'] dd figure(2) triplot(wart,x,y)

this should script. matrix generated delaunay() matlab function:

dd =  6     7     2  7     1     2  4     6     2  1     3     2  4     3     5  6     4     5  2     3     4

this implementation :

wart =  4     7     6  4     7     5  4     7     5  4     7     5  4     7     5  4     6     5  4     6     5

could of tell me wrong ? mistake or guide me?

jils.

the issue in innermost loop, here:

if (zn < 0)                 border=zn;                     m=1:length(x)                         border = (border) & ...                             ((x(m)-x(i))*xn +...                             (y(m)-y(i))*yn +...                             (z(m)-z(i))*zn <= 0);                         if (border)                          ii(m)=[i];                         jj(m)=[j];                         kk(m)=[k];                         end                     end             end

you want check if triangle defined points [i,j,k] valid. if m (no points inside circumcircle) want save 3 points output. currently, if first point check outside circumcircle, 3 points saved no matter what. in addition, since loop on same m each possible triangle, if find correct values you're overwriting them later on. why repeats of same values in output.

in these cases worth stepping through (mentally, manually on command line, or using debug methods) loops see happens. first output 4 7 6 doesn't appear in inbuilt function results. set i,j,k values , see happens in inner loop.

incidentally, don't need loop there. check values @ once doing like:

 border = (x-x(i)).*xn + (y-y(i)).*yn + (z-z(i)).*zn;  if all(border<0)     % store coordinates  end

you can start empty output ([]) , append (using end+1), or calculate max number of triangles , preallocate output size, use counter variable keep track of how many find , put them in right place in output array, , trim output size right @ end. if you're planning have larger input data sets, better preallocate.


Comments

Post a Comment

Popular posts from this blog

C# random value from dictionary and tuple -

-
i have following code, , need random item contains string "region_1" dictionary. public static dictionary<int, tuple<string, int, currencytype>> itemarray = new dictionary<int, tuple<string, int, currencytype>>() { { 0xb3e, new tuple<string, int, currencytype>("region_1", 1500, currencytype.fame) } }; public static int generateitemid(string shopid) { var generateditem = itemarray.elementat(new random().next(0, itemarray.count)).key; } how select this? it's not possible efficiently... first create static random @ class level... prevent non-random behaviour if run query on short period of time... (it's seeded discrete clock) static random rnd = new random(); then: var item = itemarray.values .where(t => t.item1 == shopid) .orderby(_ => rnd.next()) .firstordefault()
Read more

cgi - How do I interpret URLs without extension as files rather than missing directories in nginx? -

-
so i'm trying install zoneminder , have run under nginx, has few compiled files need run using fast-cgi. these files lack extension. if file has extension, there no issue , nginx interprets file , return 404 if can't find it. if has no extension, assume it's directory , return 404 when can't find sort of index page. here have now: # security camera domain. server { listen 888; server_name mydomain.com; root /srv/http/zm; # enable php support. include php.conf; location / { index index.html index.htm index.php; } # enable cgi support. location ~ ^/cgi-bin/(.+)$ { alias /srv/cgi-bin/zm/; fastcgi_pass unix:/run/fcgiwrap.sock; fastcgi_param script_filename $document_root/$1; include fastcgi.conf; } } the idea is, under cgi-bin directory goes through fastcgi pipe. any idea on howi can fix this? upon closer inspection, realized zoneminder has 2 cgi sc...
Read more

.htaccess - htaccess convert request to clean url and add slash at the end of the url -

-
ok , searched more 4 days , more 20 posts here in stach or in websites without kind of success first here htaccess file rewriteengine on rewriterule ^([a-za-z0-9_]+)/?$ index.php?page=$1 [nc] rewriterule ^([a-za-z0-9_]+)\/([a-za-z0-9_]+)\/?$ index.php?page=$1&action=$2 [nc] i tried many codes 1 worked me can call request , works me www.example.com/pagename => www.example.com/index.php?page=pagename here questions , please provide me information "in detail" understand code well 1- how convert request automatically www.example.com/index.php?page=pagename www.example.com/pagename 2- if tried add slash @ end shows me page without images or styling mean www.example.com/pagename => works www.example.com/pagename/ => doesn't work that's :) for first part need 301 rule this: rewritecond %{the_request} /index\.php\?page=([^\s&]+) [nc] rewriterule ^ /%1? [r=301,l] for second part use absolute path in css, js, images files r...
Read more