Doing the Splits Part 2: A Deeper Stretch

September 16, 2020 Scott Henderson

In my previous post we looked at some basic Split options – choosing the correct surfaces, working with a number of surfaces, and making sure that we pick the specific area of the surface that we’d like to keep. This time around, we’ll explore other options in the Split command, see what they’re for, and see why we might use them.

I’ll have one of everything

If you need to keep both sides of a split element, then “Keep both sides” is likely the obvious choice. This’ll do exactly what it sounds like it will: both sides of the split surface are kept.

As a drawback, CATIA will bury one of split objects inside of the other one in the tree.


This can potentially create some unwanted characteristics, though. For example, hiding the main Split object will not hide the sub-element, as typically expected.

Deleting the sub-element here will not work, either.

Instead, you’d have to modify the Split and disable “Keep both sides.” In addition, the sub element cannot be moved from beneath the main Split. If you’d prefer both sides to be completely separate, splitting the surface twice could be an alternative approach.


Intersections Computations

This is a relatively straightforward option that will create a wireframe representation of the split edge. If you are cutting two surfaces, then a curve will be created where those items intersect each other.

Tree-wise, the Intersect will be stored as a sub-feature of the Split.

Keep and Remove

Depending on the shape of the surface that’s being split, there may end up being several resultant surfaces. The Keep and Remove options will let you choose which of those resultant surfaces stay and which do not.

In the images below, there’s a top surface with several “fingers” shooting out the right.

These fingers extend past the pink, vertical surface. In this case, we need to trim down some of those fingers, but not all of them.

A basic trim will keep all of the extended fingers. Generally, “Elements to Remove” and “Elements to Keep” will help us modify only the pieces that we want.


Select the “Elements to Keep” option to pick the portion of the items you’d like to keep. In this case, the goal is to keep three of the fingers to the right side of the pink, vertical surface.


Note that edges are selected here to ensure that CATIA keeps the correct side of the Split. Attempting to pick a side of the top surface is potentially ambiguous, as the fingers exist to both the right and left of the vertical surface. The Split definition box shows that there are three items in selected in “Elements to Keep.”

And here are the results:


On the other hand, “Elements to Remove” is pretty much the inverse. If you’d like to keep a majority if the surfaces, use this to select the surface segments that will be removed.


And Relax

While these options may not be something you have to use every time you perform a split, it’s nice to have them when you need them. If you need to keep both sides or a Split or, just generally, be a little pickier about what you’re keeping, we’ve looked at a few ways to make that happen and a couple of things to watch out for, too.

There’s one last article in our Split series. In the upcoming Part 3, we’ll check out the last few remaining options in our Split commands – extrapolations, ignore elements, and half space.



About the Author

Scott Henderson

Technical Training Engineer<br><br>Scott Henderson is a Dassault Systèmes Certified Instructor. With expertise in CATIA, DELMIA, and ENOVIA, he has been leading training classes and providing on-site customer support since 2006, focusing primarily in the Automotive industry.

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Previous Article
Doing Splits the Easy Way: Splitting Surfaces in CATIA V5
Doing Splits the Easy Way: Splitting Surfaces in CATIA V5

The Split command is an essential tool when working with surface-based models in the Generative Shape Desig...

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Doing The Splits Part 3: The Final Stretch
Doing The Splits Part 3: The Final Stretch