How to assess the value at Mesh Vertices and convert them to Numpy Array

Hi Guys,

I would like to ask a simple question as I am quite new to the software.

Referring to: GridFunction to numpy array to new GridFunction - Kunena,

I am currently developing the rate determination scheme for the Convection-Diffusion-Reaction model, which requires the inputs as a numpy array of the values of the mesh points to the scheme for every time step. My understanding is that I cannot use the result from the GridFunction as Alex explained that “its components were the coefficients for the interpolating polynomials rather than the values at the points”.

I then found the topic (How to assess CoefficientFunction at Mesh Vertices - Kunena) which Joachim explained the approach of using IntegrationRule to get the vertices. I think that I can apply the same approach, but I am not sure that what should be the code inside IntegrationRule(…) if I would like to get all the vertices in the 3d- geometric space? Do I need the 8 corner points instead of 4 points? Can you also help me explain what the irrelevant weight is?

Thank you,