reducepatch function with stl file

How can I use reducepatch function with stl file?? Thank you

Answer 1

[Rahul]

Hi @nourdine ouzoubair,

In order to use 'reducepatch' function with an stl file, consider the following steps:

• Read the stl file using 'stlread' function.
• You would obtain a Triagulation object which would contain 'ConnectivityList' and 'Points'
• Either construct a struct with properties 'faces', 'vertices', where 'faces' would crrespond to 'ConnectivityList' and 'vertices' would correspond to 'Points' of the Triangulation object.
• You can also consider creating a 'patch' object with the 'ConnectivityList' and 'Points' as 'Faces' and 'Vertices'.
• This struct or 'patch' object created can be passed to the 'reducepatch' function with appropriate arguments.

The following MathWorks documentations can be referred:

'stlread': https://www.mathworks.com/help/matlab/ref/stlread.html

'patch': https://www.mathworks.com/help/matlab/ref/patch.html

'reductpatch': https://www.mathworks.com/help/matlab/ref/reducepatch.html

Thanks.

[DGM]

How about an example?

unzip sphere_200.stl.zip % for the forum

% read the file
T = stlread('sphere_200.stl'); % triangulation object

% convert to an FV struct
FV = t2fv(T);
size(FV.faces,1)

ans = 39996

patch(FV,'facecolor',[0.2 0.8 1],'edgecolor','none');
view(3); view(-30,47); camlight; 
axis equal; grid on

% reduce the model to 10% of the facecount
FVr = reducepatch(FV,0.1);
size(FVr.faces,1)

ans = 3998

patch(FVr,'facecolor',[0.2 0.8 1],'edgecolor','none');
view(3); view(-30,47); camlight; 
axis equal; grid on

My use of t2fv() here is both a convenience and an anachronism. In 2016, we wouldn't be reading into triangulation objects. The first-party stlread() didn't exist until late 2018. The available third party decoders would have been returning data as an FV struct, separate F,V lists, or other less useful formats. As a consequence, we would likely need to do nothing extra to obtain the FV struct.