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What is a 2D Grid? A 2D grid is a regular spatial discretization of an area into equally sized cells.
Each cell represents a spatial unit for which values (e.g. elevation, thickness, parameters) are defined. A crucial aspect of a grid definition is how the position of each cell is referenced.

Grid Cells vs. Grid Points A common source of confusion is the distinction between:

Grid cells (areas)

Grid points (coordinates) In GeoScene3D, grid-based data are internally defined using grid points, not full polygons.

Grid Origin in GeoScene3D GeoScene3D defines the grid origin (null point) at the lower-left corner of the grid. This means:

The grid coordinates start in the lower-left corner

Cell spacing is applied in positive x- and y-directions from this point This definition is consistent with many numerical and interpolation-based grid formats.

Cell Reference Point: Center of the Cell Although the grid origin is located at the lower-left corner, GeoScene3D defines grid values at the CKGE_TMP_i center CKGE_TMP_i of each cell. In practice, this means:

The first grid value is located half a cell size away from the lower-left corner

Each grid point represents the center of a grid cell, not its corner This is the key point that often causes confusion.

Effect on Visualization Because grid values are defined at cell centers, the visualization behaves as follows:

The first cell is centered around its grid point

At the grid boundary, only half of the first cell lies inside the grid extent As a result:

The first grid cell appears visually as a quarter cell in the lower-left corner This is not an error, but a direct consequence of:

the grid origin being defined at the corner, and

the grid values being defined at cell centers.

Illustration The figure below illustrates this behavior:

Grid points are located at the centers of the cells

The grid origin is at the lower-left corner

The first visible cell is therefore only partially shown This visual effect helps explain why the grid may appear “cut” at the edges.