# Add flow extension proportionnal to inlet/outlet diameter

**URL:** <https://discourse.slicer.org/t/add-flow-extension-proportionnal-to-inlet-outlet-diameter/44744>\
**Category:** Support\
**Created:** [October 13, 2025, 2:13pm UTC](https://discourse.slicer.org/t/add-flow-extension-proportionnal-to-inlet-outlet-diameter/44744 "2025-10-13T14:13:11Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![gred](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/gred/32/81172_2.png) [@gred](https://discourse.slicer.org/u/gred)\
**Post date:** [October 13, 2025, 2:13pm UTC](https://discourse.slicer.org/t/add-flow-extension-proportionnal-to-inlet-outlet-diameter/44744/1 "2025-10-13T14:13:11Z")

</div>

Dear all,

Is there an obvious way to add flow domain extensions using the Clip Vessel module proportional to the diameter of the inlet and outlet in question according to the centerline quantification table?

Best,

Gred

---

<div class="post-metadata">

**Author:** ![gred](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/gred/32/81172_2.png) [@gred](https://discourse.slicer.org/u/gred)\
**Post date:** [October 14, 2025, 1:33pm UTC](https://discourse.slicer.org/t/add-flow-extension-proportionnal-to-inlet-outlet-diameter/44744/2 "2025-10-14T13:33:27Z")

</div>

My initial question was: how, from the branch clipper module, can I apply a domain extension with a different length for each inlet/outlet?

For example:  
Inlet 1 : L = 5x diameter  
Inlet 2 : L = 6x diameter  
Outlet 1: L = 3x diameter  
Outlet 2: L = 4x diameter  
…  
etc.

Since the branch clipper module applies the same extension length to all inlets and outlets, I solved the issue by using PypePad VMTK and looping the vmtkflowextensions script as many times as there were different lengths to apply.

I hope this helps others.

Best,

Gred