System and Method for Approximating Cartographic Projections by Linear Transformation

摘要

A map element parameterized in a two-dimensional (2D) coordinate system is applied to to three-dimensional (3D) geometry, parameterized in a 3D coordinate system, of a geographic area with which the map element is associated. The 3D geometry is rendered according to the selected perspective of a virtual camera. An approximate distance between the virtual camera and the 3D geometry is compared to a threshold value. A position of the map element is determined relative to the 3D geometry using (i) a linear transformation between the 2D coordinate system and the 3D coordinate when the approximate distance is smaller than the threshold value, and (ii) a non-linear transformation between the 2D coordinate system and the 3D coordinate system when the approximate distance is larger than the threshold value.

主权项

1. A method for applying a map element parameterized in a two-dimensional (2D) coordinate system to three-dimensional (3D) geometry of a geographic area with which the map element is associated, wherein the 3D geometry is parameterized in a 3D coordinate system, the method comprising:
rendering the 3D geometry according to a selected perspective of a virtual camera; comparing an approximate distance between the virtual camera and the 3D geometry to a threshold value; determining a position of the map element relative to the 3D geometry using (i) a linear transformation between the 2D coordinate system and the 3D coordinate when the approximate distance is smaller than the threshold value, and (ii) a non-linear transformation between the 2D coordinate system and the 3D coordinate system when the approximate distance is larger than the threshold value.