# Is there any methods (like circularity) to decide if the 3D construction close to sphere?

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Dongyu Liang on 31 Jan 2021
Commented: Dongyu Liang on 4 Feb 2021
Hi,
I have got many 3D particles from 2D images and want to get a value to decide if this 3D particles close to perfect sphere. For a 2D shape, I know there is a way to calculate circularity, but is there a similar way for 3D constructions?
Thanks!
Dongyu Liang on 4 Feb 2021
They are some mineral particles scaned by micro CT, so the inputs are set of 2D images in TiF to generate 3D structure. There are only particles which have been burned before scanning. So there are voids inside the particle to become like hollow sphere. To classify the particles, I want to know if there is any concepts to describe how the shape of those particles close to hollow sphere.
Thank you.

Shubham Rawat on 3 Feb 2021
Hi,
When finding sphericity for a single particle or object, you can define sphericity as the ratio of surface area of a sphere that has the same volume as the particle or object to the surface area of the particle itself.
Put into mathematical terms, the sphericity given by ​Ψ ("psi") is:
for the volume of the particle or object ​​ and surface area of the particle or object ​​. You can see why this is the case through a few mathematical steps to derive this formula.
Hope this Helps!​
Dongyu Liang on 3 Feb 2021
Hi,
Thank you for the help.
I just realized the particles are not solid inside. Therefore, the sphericity may not be good for this. So, I am wondering is there any concepts to describe how the shape of an object close to hollow sphere?
Thanks!