# How does catia do it?

#### Lili2606

##### New member
Hi everyone,

I am writing a final year paper about Centre of Gravity and Inertia measurements, and I am trying to find some sort of information on how does Catia (V5) calculate CoG and inertia values for parts. I would be happy with equations, but if all I get to know is that it uses density and volume to figure it out somehow is also perfectly fine, as long as I can cite it.. but I just can not find any research or information paper or article or stuff about this. Does anyone know how the magic happens or knows how can I access information about it?

Thank you very much!

#### MrCATIA

##### Super Moderator
Most software developers are very protective of the proprietary algorithms they use, so it will be very difficult to learn how Dassault Systemes calculates the mass properties with CATIA. I'm sure they use the same formulas that are found in any engineering textbook (based on the material density and 3D volume), but I can only guess at how they calculate the volume to begin with.

#### Micho

##### New member
Every surface Catia uses can be depicted as a function. Then if You have the functions You can calculate double/triple integral to get volume of a solid limited with the surfaces (this is geometric interpretation, I don't remember how to do this, but there are many sources in the internet). Then if You have volume and density (which is established for a certain kind of material) You can calculate mass easly by multiplying. I guess that calculating CoG is approximated. They cut solids into volumes as small as possible and then multiply their mass and position. Later they add all this 'multiplies' up and divide into total mass of the elements. First along one direction, later along others. Then they get CoG along each direction and create a triangle with corners in this points. Then they link all the corners with opposite sides of the triangle and get total CoG at the intersection point. Feel free to quote me xD

#### Micho

##### New member
Only my guess #### Micho

##### New member
of course there is no problem to calculate Inertia then