Navigation Device 3D Map Visibility Prediction
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Solution Overview
Problem
The process of rendering 3D electronic map views in navigation devices requires significant computational resources, limiting performance due to the need for large computational efforts in calculating screen-space errors for triangular faces, which also demands substantial memory and processing power.
Innovation Solution
A navigation device with a database storing control information for nested bounding spheres of triangular faces, calculated at compile time, allows for predicting visibility based on viewing angles and camera positions, reducing the need for real-time calculations and memory usage by selectively loading only visible tiles into working memory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If rendering is performed for all triangular faces in the TIN, then complete 3D terrain representation is achieved, but computational resources and processing time are excessively consumed
Solution Approach 1:
The patent pre-calculates and stores bounding sphere information for each triangular face during the compile time phase. This preliminary preparation enables rapid visibility determination during runtime without performing complex geometric calculations, thus resolving the contradiction between complete terrain representation and rendering performance by preparing data in advance.
Solution Approach 2:
The patent extracts only the essential bounding sphere information from each triangular face and stores it in a compact form. This extraction allows the system to determine visibility with minimal data, avoiding the need to process complete triangular face geometry during rendering, thereby improving performance while maintaining terrain representation quality.
2Measurement precision
If screen-space error calculation is performed for each triangular face to determine visibility, then rendering accuracy is improved, but computational resources are significantly consumed
Solution Approach 1:
The patent replaces expensive screen-space error calculations with a simple bounding sphere containment test. This cheaper alternative uses pre-computed sphere data to quickly determine visibility without requiring complex real-time calculations, significantly reducing computational resource consumption while maintaining adequate visibility determination accuracy.
Solution Approach 2:
The bounding sphere parameters are pre-calculated and stored during compile time, transforming the expensive runtime calculation problem into a simple data lookup operation. This preliminary preparation eliminates the need for complex computations during rendering, resolving the contradiction between accuracy and computational cost.
3Measurement precision
If high resolution TIN is used for all tiles, then terrain detail quality is maximized, but memory requirements and processing load increase
Solution Approach 1:
The patent applies different resolution levels to different spatial regions based on their importance. Tiles closer to the camera or containing important features use higher resolution TINs, while distant or less important tiles use lower resolution. This local differentiation maintains terrain detail quality where needed while reducing overall memory usage and processing load.
Solution Approach 2:
Instead of applying uniform high resolution to all tiles, the patent applies high resolution only partially to the most critical regions. This partial action approach provides sufficient terrain detail quality for important areas while avoiding the excessive memory and processing requirements of universal high-resolution rendering.
Data Source
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AI summary
A navigation device (1) for a vehicle (8) comprises a database (2a, 2b) storing, for a plurality of tiles of a tiling, at least one triangulated irregular network, TIN, defining a three-dimensional surface, and, for a plurality of triangular faces of the at least one TIN, control information defining a nested bounding sphere for the respective triangular faces. The navigation device (1) comprises further a processor (3) coupled to said database (2a, 2b), configured to calculate a screen-space error for the plurality of triangular faces based on the respective control information (16) and based on at least one of the following: a viewing angle of an electronic map view, a virtual camera position of the electronic map view. The processor is configured to predict whether a triangular face is visible in the electronic map view based on the calculated screen-space error.