Surface normal and tangent directions

VisualFEA uses surface normal directions for various purposes including model rendering, force assignment, local coordinates of a shell element and so on. The normal direction at a specific point on a surface mesh is determined by the element containing the point. It is related to the node numbering within the element. The tangent directions are especially important for a shell element with its local coordinates based on the surface normal and tangent directions. They are defined by the surface normal and the global coordinate axes. You can identify the surface normal and tangent directions, and reverse the directions if necessary.

<Node numbering and normal direction on an element>

> Displaying the surface normal direction

To display the surface normal, select surface meshes whose normal directions are to be displayed. And choose the "Normal" item of submenu. Then, a surface normal vector is drawn at the center of each element constituting the surface meshes.

<Example of reversing surface normal direction>

> Displaying surface tangent directions

There are two tangent directions which makes 3 orthogonal axes along with the surface normal. The tangent directions are also the local coordinates axes used in shell elements. To display the directions tangent to the surface, select surface meshes whose tangent directions are to be displayed. And choose the "Tangent (Local x)" or "Tangent (Local y)" item of submenu. The local x direction of a shell element is displayed by selecting "Tangent (Local x)" item, and the local y direction by "Tangent (Local y)".

> Reversing surface normal directions

The surface normal directions can be reversed by selecting surface meshes and choosing "Reverse" item of submenu. Reversion of a normal vector on an element results in reversing the node numbering within the element.