# Parent map domain for FreeFem

**URL:** <https://community.freefem.org/t/parent-map-domain-for-freefem/2713>\
**Category:** General Discussion\
**Created:** [September 19, 2023, 9:40am UTC](https://community.freefem.org/t/parent-map-domain-for-freefem/2713 "2023-09-19T09:40:28Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Erika](https://avatars.discourse-cdn.com/v4/letter/e/47e85d/32.png) [@Erika](https://community.freefem.org/u/Erika)\
**Post date:** [September 19, 2023, 9:40am UTC](https://community.freefem.org/t/parent-map-domain-for-freefem/2713/1 "2023-09-19T09:40:28Z")

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Hi,

I need to implement a definition where the map from parent to physical domain is required. How can I find the parent domain? There is anyone who has already implemented a map from parent to physical domain in FreeFem? How can I compute it?

Thanks,

Erika

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**Author:** ![marchywka](https://avatars.discourse-cdn.com/v4/letter/m/ee59a6/32.png) [@marchywka](https://community.freefem.org/u/marchywka)\
**Post date:** [September 20, 2023, 3:07pm UTC](https://community.freefem.org/t/parent-map-domain-for-freefem/2713/2 "2023-09-20T15:07:18Z")

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Do you have a specific example or citation/link to further explanation?

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**Author:** ![Erika](https://avatars.discourse-cdn.com/v4/letter/e/47e85d/32.png) [@Erika](https://community.freefem.org/u/Erika)\
**Post date:** [September 25, 2023, 8:43am UTC](https://community.freefem.org/t/parent-map-domain-for-freefem/2713/3 "2023-09-25T08:43:52Z")

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The article reads as:

_[…] G is the inverse Jacobian of the element mapping between the parent and the physical domain […]_

I thought that it is the map between the reference element and the physical one. However, I am not sure about what is the reference element on FreeFem. I made the hypothesis of a reference isotropic triangle, but if someone can confirm my hypothesis, it would be better.

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**Author:** ![marchywka](https://avatars.discourse-cdn.com/v4/letter/m/ee59a6/32.png) [@marchywka](https://community.freefem.org/u/marchywka)\
**Post date:** [September 25, 2023, 10:48am UTC](https://community.freefem.org/t/parent-map-domain-for-freefem/2713/4 "2023-09-25T10:48:56Z")

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Can you post more context? It may be obvious to someone with more FEM  
experience but I’m not sure what you are after. AFAICT FreeFem elements  
are triangles and tetrahedrons in 3D with a variety of test functions.