# Build VTK with external VTK-m

**URL:** https://discourse.vtk.org/t/build-vtk-with-external-vtk-m/15228
**Category:** Support
**Created:** [January 30, 2025, 8:10pm UTC](https://discourse.vtk.org/t/build-vtk-with-external-vtk-m/15228 "2025-01-30T20:10:37Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![Dave-Allured](https://discourse.vtk.org/user_avatar/discourse.vtk.org/dave-allured/32/7698_2.png) [@Dave-Allured](https://discourse.vtk.org/u/Dave-Allured)
#### Post date: [January 30, 2025, 8:10pm UTC](https://discourse.vtk.org/t/build-vtk-with-external-vtk-m/15228/1 "2025-01-30T20:10:37Z")

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What is the correct option to build VTK with an external VTK-m module, rather than the built-in copy? The build options documentation indicates `VTK_MODULE_USE_EXTERNAL_<name>`. I have tried several permutations of `<name>`, also forum and source code searches with no working answer so far. Thank you for any advice.

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### Author: ![ben.boeckel](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/b/ea5d25/32.png) [@ben.boeckel](https://discourse.vtk.org/u/ben.boeckel)
#### Post date: [January 31, 2025, 7:40pm UTC](https://discourse.vtk.org/t/build-vtk-with-external-vtk-m/15228/2 "2025-01-31T19:40:43Z")

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Not all third party packages support that option because they are either “always external” (e.g., Catalyst and MPI) or are always internal (VTK-m being one of them). I’m interested in support an external build, but it hasn’t been done yet.

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### Author: ![Dave-Allured](https://discourse.vtk.org/user_avatar/discourse.vtk.org/dave-allured/32/7698_2.png) [@Dave-Allured](https://discourse.vtk.org/u/Dave-Allured)
#### Post date: [January 31, 2025, 9:03pm UTC](https://discourse.vtk.org/t/build-vtk-with-external-vtk-m/15228/3 "2025-01-31T21:03:43Z")

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Ben, thanks for that info. I look forward to external build whenever it will be available. I am trying to improve support for MacPorts, and I prefer to break up very large builds into modules, when possible.