The hull surface must be represented by a sufficient number of quadrilateral and/or triangular panels.

The panel normals must point towards the surrounding fluid field, as discussed in Equation 3–1.

The hull surface, especially the mean wetted hull surface part, must be fully covered by panels without gaps or overlap between panels.

The mean wetted hull surface is required when the source distribution approach is used in a frequency domain analysis. The hull surface above the mean water level may be needed when doing a nonlinear time domain analysis. For such cases, both the mean wetted hull surface and the hull surface above mean water level may be modelled by panels. These panels must not cut the mean water surface. All the panels not involved in Equation 4–24 are referred to as non-diffracting panels.

Each individual panel must satisfy the following requirements:

The panel center must not be too close to the adjacent panel centers:

(4–27)

where is the distance between the center of the m-th panel to the center of the adjacent panel and is the radius of the m-th panel which is defined as

If a fatal error is issued.

The panel shape must be regular. To quantitatively check this requirement, a shape factor for the panel is introduced:

(4–28)

where is the number of panel sides (4 for quadrilateral panels and 3 for triangular panels) and

where are the nodal coordinates of any 3 nodes of the m-th panel in order and is the coordinates of this panel center.

With this definition, it is required that

(4–29)

The panel size should be small relative to the wave length:

(4–30)

The centers of the diffracting panels must be above the seabed to avoid any singularity of the Green's function (given by Equation 4–18):

(4–31)

where is the Z-coordinate of the center of the m-th panel in the fixed reference axes (FRA) and is the panel radius defined in Equation 4–27.