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## Supplemental Information

### Illustration of the voxelization process for a sphere

Illustration of the voxelization of a sphere within coarse mesh elements. The sphere is indicated by the yellow surface while the thick black lines outline the elements of the actual mesh. The voxelization within elements follows the Octree refinement towards the sphere and is indicated by the thinner white lines. Inside the sphere, voxels have been colorized by the flood-fill mechanism with a seed in the center. Flooded elements are shown in red; other elements are blue.

### Illustration of sphere approximations with various accuracy

Illustration of sphere approximations, with increasing accuracy. The sphere is blue, and the isosurface of the color value at 0.5 is yellow. On the left, the sphere is shown in the embedding domain with the 8 elements. Voxelization and integration points increase from left to right.

### Illustration of varying number of integration points for a cube

Representation of the cube in 8 elements with polynomials of degree 15. From left to right an increasing number of integration points is used. The leftmost image shows the cube with the 8 elements of the mesh. The reference geometry is drawn in blue, and the isosurface of the color value 0.5 in yellow. We cut the reference in the middle to enable a better view for the comparison, except for the second image, where it is the other way around, and the isosurface is cut.

### Illustration of varying polynomial degrees in the approximation of a tetrahedron

Approximation of the tetrahedron with an increasing polynomial degree from left to right. Starting on the left with a polynomial degree of 7 and increasing over 15 and 31 to 63 in the rightmost image. Shown is the isosurface of the polynomial at a value of 0.5 in yellow and for comparison the reference geometry cut in half with a blue coloring.

### Example for the application to a complex geometry like a porous medium

Isosurface of a porous medium (yellow) in comparison to the original STL data (blue). The geometry is well recovered; only edges are smoothed out a little.

### Illustration for the use of a generated geometry representation in an electrodynamic wave scattering setup

Scattering of a planar wave at a cylindrical object. The grid lines indicate the mesh of the DGFEM solver. For the numerical solution, a basis with a maximal polynomial degree of 15 is used. On the left, the reference solution is shown. On the right, the difference between the numerical solution and the reference can be seen for a de-aliasing by 32 points. The color scale for the difference is chosen with a range of +/- 10 % of the maximal amplitude in the reference.

### Competing Interests

The authors declare that they have no competing interests.

### Author Contributions

Harald G Klimach wrote the paper, prepared figures and/or tables, performed the computation work, reviewed drafts of the paper.

Jens Zudrop performed the computation work, reviewed drafts of the paper.

Sabine P Roller wrote the paper, reviewed drafts of the paper.

### Data Deposition

The following information was supplied regarding data availability:

https://bitbucket.org/apesteam/seeder

### Funding

The authors received no funding for this work.

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