Mathematical principle of three-dimensional modeling?

1. Three-dimensional modeling

1. Manual modeling

Obtaining data: using GNSS-RTK or total station

modeling software: using traditional three-dimensional modeling software such as 3DSMax, Skyline and SketchUp to manually model.

method principle: a three-dimensional model without texture is established on the basis of plane information. The texture in the model needs to be photographed manually and pasted on the three-dimensional model.

disadvantages of this method: heavy workload, time-consuming and laborious, high production cost and low efficiency.

2. traditional remote sensing technology, satellite and aerial photogrammetry technology

method principle: using fast image matching technology to generate DOM requires manual or semi-automatic collection of artificial ground objects to obtain the building surface texture of the image. Finally, three-dimensional modeling based on high-resolution images is realized.

Advantages of the method: Remote sensing images have wide coverage, low cost and high resolution, so accurate data can be obtained quickly. Disadvantages of this method: there is a serious occlusion problem in 3D modeling, the acquisition cost of building facade texture data is high, and the indoor mapping is time-consuming and laborious.

second, tilt photogrammetry

principle: tilt photogrammetry is to collect image data from vertical, tilt and other angles with a five-lens camera on the same drone to obtain complete and accurate texture data and positioning information.

technical advantages: high resolution, rich texture information of ground objects, efficient and automatic 3D model production, and realistic 3D space scene

Disadvantages: oblique photography technology uses visible light to measure, which requires high weather, and is powerless to the terrain under dense vegetation, and lacks the modeling ability of small objects.

Applicable scene: Tilt photography can obtain 3D data with real texture, which is suitable for large-scale 3D modeling and some 3D engineering survey applications with lower accuracy requirements.

iii. lidar measurement

principle: the lidar system includes a laser and a receiving system. The laser generates and emits a light pulse, which hits the object and reflects back, and is finally received by the receiver.

three-dimensional modeling mainly adopts graphic theories such as ConstructiveSolidGeometry-CSG1 and geometric features of shapes.

CSG is an analysis of the overall formation of an entity, that is, any complex entity can be regarded as a combination of simple units. Similar to the shape analysis method of an assembly in engineering drawing, an object is decomposed into several basic units (that is, units), and this combination is generally realized by Boolean operations (union, difference and intersection).