Fitting a cilinder to 3D vertices

I am having problems fitting a cylinder to a point cloud. Trying to use "pcfitcylinder", an error saying 'the value of 'ptCloud' is invalid. Expected ptCloud to be a pointCloud object' while the pointcloud is a nx3 created from the vertices of an .stl file. The code is:

Bone_model=stlread(fullfile(Bone_path,Bone_file));

maxDistance=.5
cilinder = pcfitcylinder(Bone_model.vertices,maxDistance);

pcshow (Bone_model.vertices);hold on;
plot(cilinder)

Is there anything i'm doing wrong?

[KSSV]

It is expecting a different input.....read the documentation.

Answer 1

[Walter Roberson]

stlread() appears to be one of the functions from the File Exchange, probably https://www.mathworks.com/matlabcentral/fileexchange/22409-stl-file-reader

The vertices returned by that stlread() function are configured for use by patch(). pcfitcylinder() requires that a pointcloud object be passed in.

You might be able to use

pc = pointcloud(Bone_model.vertices);
[cilinder,inlierIndices] = pcfitcylinder(pc, maxDistance);
cylpc = select(cilinder, inlierIndices);
pcshow(cylpc)

Note that pcfitcylinder attempts to find a subset of the pointcloud that is in the form of an cylinder.

[Daniel Devaprakash]

Hi Walter,

I used the syntax specified in your answer to fit a cylinder to a bone, and I get the following error message:

             No appropriate method, property, or field 'Normal' for class 'pointCloud'.
             Error in pcfitcylinder (line 118)
             if isempty(ptCloud.Normal)

I tried to write include the normal values using the following syntax:

                 TalusPtCloud = pointCloud(Talus.solidVertices{1,1}, 'Normal', Talus.solidNormals{1,1});

I see the following error message:

                Error using pointCloud (line 171)
'Normal' is not a recognized parameter. For a list of valid name-value pair arguments, see the documentation for this function.

Could you please provide any advice on how to solve this issue? Thank you for your time.

Cheers,

Danny

[Walter Roberson]

Which MATLAB version are you using?

[Daniel Devaprakash]

Hi Walter,

I am using 2017b.

Cheers,

Danny

[Walter Roberson]

I suspect that you are getting some other pointCloud() routine. 'Normal' has been supported for a number of releases

https://www.mathworks.com/help/releases/R2017b/vision/ref/pointcloud-class.html

What shows up for

which -all pointCloud

? You should expect something like

toolbox/vision/vision/pointCloud.m

In your release, line 171 of pointCloud (the line number giving the error in your error message) is in the middle of a block of comments.

[Daniel Devaprakash]

Hi Walter,

Thank you very much for your help. Yes, I had two files named as pointCloud.m (second one downloaded from MATLAB central).

Thanks again for your help.

Cheers,

Danny

[M.S. Khan]

Hi Danny,

could you please explain the coding to me. i also want to apply it on my problem.

Warm regards,

[Walter Roberson]

M.S. Khan, which coding are you referring to? The only line of code that Daniel posted was

                 TalusPtCloud = pointCloud(Talus.solidVertices{1,1}, 'Normal', Talus.solidNormals{1,1});