Some understandings of 3dfiles

Because of the need of work , Need to put OSGB The file is converted to 3D Tiles, For network transmission and Web Display of platform, etc .OSGB Mainly from tilt photogrammetry , It can be done by smart3D（ Old name ） Three dimensional modeling results ;3D Tiles For streaming 3D Content , Including buildings 、 tree 、 Point cloud and vector data . At present, from the experience of the project , It's only used. OSGB Image data is converted to 3D Tiles The situation of . Because it's Xiaobai , Learn from the beginning , First of all, we need to understand the organizational format of various documents , Such as osgb file 、tileset.json file , Now let's introduce it according to our own understanding Tileset The format of , First, deepen your understanding , Second, I hope it will be helpful to students who are just beginning to learn like me .Tileset With an example .

From the root directory , There are three properties ,“asset”、“geometricError”、“root” Three attributes , Let's talk about .

1.asset 

asset Including the whole tileSet Metadata , Include “version” Defined 3D Tiles Version of , This version number specifies tileSet Of JSON Patterns and basic tileSet Format ."gltfUpAxis" Definition gltf The axis above the file .

2.geometricError

geometricError To determine the tile The resolution of the , Calculate the screen error through this set error , determine tileSet Whether to render .

3.root

root What's in store is tileset The content of , Let's expand root Field content of , Detailed introduction root Medium Content .

3.1 boundingVolume

boundingVolume To determine the tileset The bounding box of .

“box” share 12 Parameters , According to my understanding , Can be divided into four groups , That is, they represent vertices 、x The vector in the axial direction 、y The vector in the axial direction 、z The vector in the axial direction .

3.2 Children

That is root tileset A subdirectory , Contains a series of side-by-side subdirectories , Explain one of them carefully .

You can see that the subdirectory contains “boundingVolumn”、“content"、“geometricError” attribute , among “boundingVolumn”、“geometricError” I've said that before ,“content” Represents a subdirectory json Relative paths .

3.3 “transform”

Express tileset The transformation matrix of , common 16 Parameters , representative 4*4 matrix , Row vectors are preferred , Execute by right multiplication .