MATLAB: Calculate volume under of 3D isosurface plot

3d visualisationdata analysisimage processingisosurfaceMATLABvolume calculationvolume visalisation

I have a 3D matrix data V(201,101,101). I want to calculate the isosurface volume for a particular isovalue.
How to calculate the volume.
I used following code to generate isosurface.
figure;
p = patch(isosurface(x,y,z,V,-2));
isonormals(x,y,z,V,p);
cdata = smooth3(rand(size(V)),'box',7);
isocolors(x,y,z,cdata,p)
p.Facecolor = 'interp';
p.Edgecolor = 'none';

Best Answer

What isosurface and isovalue are doing are generating a surface around those points that are above a certain value. All code you showed is good for visualising, but what you really want here is not a visual display but a number of the volume.
If you want the volume that is the same as how many points satisfy your condition of voxel intensity > value, so what you have to do is the following:
volumeOfInterest = (V >-2 );
That will generate a matrix of same dimensions as V with 1 for those points above the isovalue and 0 below, then simply sum those values
volume = sum (volumeOfInterest(:));
And then, if needed you will need to callibrate that value to the physical quantity of your interest (say mm^3) with a conversion between voxels and that quantity.
Hope that helps
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