# Preprocessing

Divide each wall into tiles and each edge into segments. Use these tiles and segments to determine the visibility relations between these elements for the propagation paths in the prediction.

- The accuracy of the prediction will increase because the rays are determined more precisely.
- The computation time (of the preprocessing and the prediction) will increase because more visibility relations have to be computed (at preprocessing time) and checked (at prediction time).
- The size of the database file after preprocessing will increase because more visibility relations have to be stored.

You can specify the maximum size of the tiles and the segments. Appropriate values would be 1 – 3 meters for the tiles and 2.5 – 3.5 meters for the segments. The appropriate maximum sizes depend on the structure of the building. The smaller the rooms, the smaller the maximum sizes should be chosen. The size of the segments is less critical than the size of the tiles. If the maximum size of the segments is chosen too large, the effects on the prediction are smaller. Therefore the maximum size of the segments can be chosen higher than that for the tiles.

If a wall is smaller than the chosen maximum tile size or if an edge is smaller than the chosen maximum segment size then the wall or segment is treated as a whole part, but it is not combined with other or edges.

Resolution for the Discretization [m] | Preprocessing Time [s] | Size of the Preprocessed fFle [MB] | Prediction Time [s] |
---|---|---|---|

1 | 7212 | 51.6 | 110 |

1.5 | 1835 | 24.9 | 100 |

2 | 1095 | 12.2 | 67 |

2.5 | 680 | 7.3 | 16 |

3 | 457 | 3.2 | 1 |

Table 1 tabulates the dependencies of the preprocessing time, size of the preprocessing file and the prediction time for different resolution values used for the discretization of the building database shown in Figure 1, thus an extension of the tiles and segments while the resolution of the receiving points remains constant at 1 m.