Find boundary vertice of 3D volume data

How can I find the boundary vertices of 3D volume data with 2 openings, the desired output should be two sets of boundary vertices. Thanks a lot.

Answer 1

[Image Analyst]

I don't see how you get two sets of coordinates. I'm thinking of a torus with two holes. To get the boundary vertices you can subtract the morphological erosion from the original binary image:

binaryImage = grayImage > someThreshold;
boundary = binaryImage - imerode(binaryImage, true(3,3,3));

or something like that.

[Patrick]

Thank you for your help but seems your codes are for image. Can you refer to the figure I have uploaded again? thanks!