Lifting a Triangulation<2> to Triangulation<2,3>

[jaosch]

Hello,

I am new to deal.ii and try to create a simple 2D mesh that lives in 3D space.

My starting point is the following code:

Triangulation<2> my_triangulation;

GridGenerator::hyper_ball(my_triangulation);

Is there a built-in function to convert my_triangulation to type Triangulation<2,3> so I end up with a 2D surface in 3D space?

Best regards

Jasper

[Bruno Turcksin]

Jasper,

You don't want to use GridGenerator::hyper_ball. Instead try:

Triangulation<2,3> my_triangulation;

GridGenerator::hyper_shell(my_triangulation);

Note that you need to use a triangulation where dim is different than spacedim.

Best,

Bruno

[Wolfgang Bangerth]

On 8/19/24 03:46, jaosch wrote:
>
> My starting point is the following code:
>
> Triangulation<2> my_triangulation;
> GridGenerator::hyper_ball(my_triangulation);
>
> Is there a built-in function to convert my_triangulation to type
> Triangulation<2,3> so I end up with a 2D surface in 3D space?

For some of the other functions in namespace GridGenerator, if you
declare the triangulation as
Triangulation<2,3> my_triangulation;
then everything just magically works. I recognize that
GridGenerator::hyper_ball() is one of those functions that do not take a
second template argument for spacedim!=dim.

Rather than think about how to work around this limitation, would you
perhaps be interested in simply adding the spacedim argument to the
implementation of this function and create a pull request that adds this
functionality? In the end, all that needs to happen is that the last
component of all vertex locations needs to be set to zero. We would, of
course, be quite happy to walk you through the process of creating a
pull request!

Best
Wolfgang

[jaosch]

Hi Bruno, hi Wolfgang,

thank you for the replies.

Unfortunately, using GridGenerator::hyper_shell() is not an option, as it does not allow

the inner radius to be zero. Adding spacedim != dim to GridGenerator::hyper_ball() is

a good I idea and something I might consider doing in a couple of months, once I have

gained a better understanding of the more fundamental parts of deal.ii.

Best regards

Jasper

[Wolfgang Bangerth]

On 9/10/24 01:00, jaosch wrote:
>
> Unfortunately, using GridGenerator::hyper_shell() is not an option, as it
> does not allow the inner radius to be zero. Adding spacedim != dim to
> GridGenerator::hyper_ball() is a good I idea and something I might consider
> doing in a couple of months, once I have gained a better understanding of
> the more fundamental parts of deal.ii.

Sounds good. Let us know if you have questions!

Best
W.
--
------------------------------------------------------------------------
Wolfgang Bangerth email: bang...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/