bovenvlak

Bovenvlak is a Dutch term used in geometry and related disciplines to denote the upper surface or top plane of a three‑dimensional object. It is defined relative to a chosen reference frame and is often discussed in contrast to ondervlak (the lower surface).

In polyhedral geometry and three‑dimensional modelling, the bovenvlak is typically the face with the greatest altitude in the chosen orientation, or the exterior face that is locally highest when projected onto a base plane. In digital terrain models and architectural modelling, the concept helps describe the upper boundary of a volume, useful for volume calculations, rendering, and simulations.

Because the designation depends on the reference frame, there is no single universal bovenvlak independent of orientation. Materials, geographies, or simulations may label different surfaces as the bovenvlak depending on the direction considered vertical or up.

See also: polyhedron, top face, upper hull, elevation model, terrain modelling. References: Dutch mathematics glossaries and geometry texts often describe upper and lower surfaces using bovenvlak and ondervlak.