Three-dimensional fine monomer modeling scheme?

1. Monomer method for 3D model of oblique photography.

At present, the single modeling method of oblique photography mainly includes the following three categories:

1. 1 vector cutting monomer

Cutting and singulation is to segment the triangular surface of an object, which realizes the model singulation operation in a certain sense, and can also manage and apply the singulated model in the later stage.

However, this editing model produces a large amount of data, which will destroy LOD and the data can only be imported separately. The single model made by this cutting method has poor effect, and there will be obvious sawtooth and irregular shape at the bottom of the edge, which is slightly lacking in later management and application.

1.2 vector superposition monomer

This method is mainly the application of typical GIS software such as SuperMap. In 3D rendering, the corresponding vector plane is dynamically superimposed in the oblique photography model, and the bounding box generated by the vector plane in the direction perpendicular to the ground will not exceed a specific threshold range.

Combined with the judgment of triangulation in the range, through the fitting and triangulation of translucent colors, the complete display of the model is realized visually, and the management of individual operations is realized.

However, this method is actually not about the separation of monomers. Although its surface can achieve the effect of monomer, in fact, it only calls the vector surface of the object contour. From a real point of view, the goal of monomer is not monomer, but separation.

1.3 model reconstruction monomer

Monomorphism of model reconstruction refers to the separation effect on the original scene through model reconstruction based on oblique photogrammetry data, so as to realize the singularity of the model. The model map is automatically collected from the image, and the model map is completed by mapping.

Compared with vector superposition, this method requires more manpower and focuses on the provision of products, which is not suitable for GIS.

Second, the production process of monoclinic photography three-dimensional model

Different monomer methods have different processes. This paper mainly introduces the way of model reconstruction monomer, and takes DP-modeler as an example.

As mentioned above, model reconstruction is based on continuous tilt photogrammetry data, and the model is reconstructed on the basis of the original real three-dimensional model, so as to simplify the models of different objects.

2. 1 is transformed into a three-dimensional model by extrusion operation.

When the building is single, we should choose the polygon drawing tool to extract the top outline of the building from the perspective image.

According to the inclined image, the height of the building is judged, the datum plane is set, and the plane model is transformed into a solid model through extrusion operation.

Stretch the column to a specified height, and then create the three-dimensional surface of the building and the ancillary structures of the building, such as eaves, parapets, unit doors, holes, etc. by using operations such as internal deviation, external expansion and cutting.

2.2 One-key mapping

One-click mapping is carried out on the built monomer model, and the texture features of different levels of the building are collected by oblique images, and the model map is automatically collected from the camera image, and then the monomer model is mapped by one-click.

For some unsuitable faces, you can manually map them by selecting the best image to achieve the best effect required by the 3D model. The model drawings obtained by automatic mapping and manual mapping inevitably have defects. We can modify the texture by calling PS, and the saved map can be directly replaced under DP-modeler without looking for a map.

Three, building contour acquisition technical standards

3. 1 technical requirements for contour acquisition

The collection of building contour lines is the basis of subsequent building 3D models. When collecting contour lines, vector collection shall be carried out according to the following rules.

Flat-topped building, collected along the edge of the building;

For herringbone roofs, collect twice. First, collect the edge lines of the building to make them form a right angle, then collect the ridge lines at the top of the building, pull them up to the actual height and hook out the inclined plane;

For complex structures, it is necessary to collect the closed outer contour line, each ridge line and the contour line of the roof protruding structure with the same height in turn. For a circle or arc, connect five or six points to represent it.

3.2 Data acquisition indicators

(1) Suburb: built on a house, with a height of > 2.5 meters and an area of > 5 square meters; Basic room, height > 2.5 meters, area > 5 square meters. Urban area: built on houses, with a height of > 2.5 meters and an area of > 2 square meters; Basic room, height > 2.5 floor, area > 2 square meters.

(2) Under the condition of maintaining the appearance of the original house, houses with height difference less than 0.5m and horizontal bend less than 0.5m can be appropriately integrated as appropriate.

(3) The building must be carried to the foundation building, and adjacent houses must be adjacent without gaps.

(4) The construction line must be even and orderly.

(5) High-end residential buildings, shopping malls, enterprises, institutions, schools, hospitals and other buildings along the street, where the parapet is more than 0.5 meters and the width is more than 0.5 meters, it shall be indicated separately; High-grade residential buildings are connected with shopping malls, enterprises, institutions, institutions, schools, hospitals and industrial and mining buildings on both sides. Where the parapet height is greater than 1.5 meters (except billboards), the parapet needs to be expressed separately, and the parapet needs to be expressed in the form of buildings on the house.

3.3 Requirements for obtaining models at different levels

(1) The concave and convex parts of government buildings, commercial buildings and public buildings larger than 0.5m shall be collected.

(2) The concave and convex parts of buildings along the street larger than 0.8m need to be collected.

(3) The cornice, decorative wall and other structures of buildings larger than 0.8m should be collected according to the actual size and shape, and the details can be represented by diagrams.

(4) Prominent foyer and entrance doors need to be collected.

(5) The top structure of the building needs to be collected according to the actual situation, and the scale and structural shape cannot be inconsistent with the actual situation.

(6) The parapet of the building needs to be levied according to the actual height and width, except for the houses built by residents.

(7) If the building area along the street is small and there are many areas, such as shutters and railings, it can be made into blocks and the images can be pasted directly.

(8) The decorative column (wall line) on the important surface of the building needs to be collected when the unevenness exceeds one meter.

(9) Building pier: the diameter is greater than 1m and the height is greater than1.5m. ..

(10) The fence needs to be collected.

(1 1) Roof decoration: Geometrical figures with projection surface larger than 4 square meters or longest side larger than 2 meters must be collected.