Grid Overlay: Difference between revisions
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When the calculation is completed, a final result value is stored in the cell. The value stored in the cell itself is a unitless number. The exact meaning of the number is dependent on the overlay which defines the calculation. A calculation for [[Traffic Noise (Overlay)|noise]] will present its result in decibels. A calculation for [[Subsidence (Overlay)|subsidence]] in meters. | When the calculation is completed, a final result value is stored in the cell. The value stored in the cell itself is a unitless number. The exact meaning of the number is dependent on the overlay which defines the calculation. A calculation for [[Traffic Noise (Overlay)|noise]] will present its result in decibels. A calculation for [[Subsidence (Overlay)|subsidence]] in meters. | ||
==Grid size== | |||
The more cells that need to be calculated, the more resources (and in the end: time) it will take to complete the calculation. Depending on the use-case and the calculation being performed, it may be desirable to change the grid size used for the grid overlays. Note that all grid overlays share the same grid size. For performance reasons it is not possible to set overlays to differing grid sizes in the same project. | |||
Revision as of 15:09, 13 September 2018
What is a grid overlay
A grid overlay is a calculated overlay. The calculation divides the entire 3D world up into a grid of cells, with cells ranging from 0.25m² to 100m². This amounts to anywhere from thousands to millions of cells per overlay. For each cell, a calculation is performed, the specifics of which depend on the overlay being calculated.
How are grid calculations performed
Depending on the exact overlay being calculated, the specifics of the calculation may differ, but the general approach is identical for each overlay. Each calculation relies on some data, which may be set as properties or attributes of the overlay, or may be based on the features present in an individual cell. This data is read from their respective locations as input for the calculation. Data from surrounding cells may also be included, in which their distance may also be factored in. With all the data obtained, a new values or set of values is calculated for the cell, and stored as result data for that cell. The calculation may specify this processing repeating a large number of times, for example when iterating through time steps.
When the calculation is completed, a final result value is stored in the cell. The value stored in the cell itself is a unitless number. The exact meaning of the number is dependent on the overlay which defines the calculation. A calculation for noise will present its result in decibels. A calculation for subsidence in meters.
Grid size
The more cells that need to be calculated, the more resources (and in the end: time) it will take to complete the calculation. Depending on the use-case and the calculation being performed, it may be desirable to change the grid size used for the grid overlays. Note that all grid overlays share the same grid size. For performance reasons it is not possible to set overlays to differing grid sizes in the same project.