MedicalVisualization

## Partial Derivatives

For the pixel-based iso-contouring approach we need the partial derivatives of the scalar field.

Either this is available directly by deriving the scalar function along dx and dy, or the scalar function is available as a height field, that is a discrete 2D grid.

In the latter case the partial derivatives cannot be calculated in closed form, but need to be approximated by the so called finite differences method.