Hello, I was wondering if there was a way to convert an imported STL file to a 3D point cloud or alpha shape. Thanks
MATLAB: STL to Point cloud or Alpha shape
MATLABMATLAB and Simulink Student Suite
Related Solutions
Perhaps this is what you are trying to do,
[x1,y1,z1] = sphere(24); %Given points (example)
x1 = x1(:); y1 = y1(:); z1 = z1(:);P = [x1 y1 z1];P = unique(P,'rows');shp = alphaShape(P(:,1),P(:,2),P(:,3),1);[F,V]=boundaryFacets(shp);F=F.'; V=V.';Q=mean(reshape(V(:,F),3,3,[]),2);Q=num2cell(reshape(Q,3,[]).',1);[x2,y2,z2]=deal(Q{:}); %"Interpolated" points
hold onplot(shp);hg=scatter3(x1,y1,z1,'SizeData',50,'MarkerFaceColor','red','MarkerEdgeColor','none');hi=scatter3(x2,y2,z2,'SizeData',50,'MarkerFaceColor','blue','MarkerEdgeColor','none');legend([hg,hi],'Given Points','"Interpolated" Points');hold off
Below code is a good example for creating a STL file for 3D geometry, read the STL as traingulation object, save it as bitmap image and calculate the volume:
Script to create a STL file for 3D geometry. eg: cylinder
[X,Y,Z] = cylinder(r,100);DT = delaunayTriangulation(X(:),Y(:),Z(:));TR = triangulation(DT.ConnectivityList,DT.Points);[F,P]=freeBoundary(TR);TR = triangulation(F,P);stlwrite(TR,'stl_test000.stl');Method 1: may not be accurate for complicated shapes
%read the stl as a triangulation
gm = stlread('stl_test000.stl');% use alphashape to create a bounding volume
shp=alphaShape(gm.Points);plot(shp)% If the plot does not look like the shape that you are expecting, change
% the critical radius for the alphashape
shp.Alpha = 5;plot(shp); % this should plot the cylinder. the plot can be saved as a bitmap
% Get the volume value
shp.volumeMethod 2: more accurate. Needs PDE Toolbox
pdem = createpde;importGeometry(pdem,'stl_test000.stl');% plot the geometry (3D)
pdegplot(pdem); % the plot can be saved as a bitmap
% mesh the geometry. For more accuracy, adjust the Hmax
msh = generateMesh(pdem,'Hmax',0.1);% calculate the volume
msh.volume()
Best Answer