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OGC 3DTiles
Open OGC 3DTiles Resource
To open an OGC 3DTiles resource, drag and drop the root file .json, which describes the structure of the tiles, or create the Orbit .3dtiles resource reference file, an empty ascii file having the same name as the .json root file (e.g. tileset.json, tilset.3dtiles).
OGC 3DTiles can be visualized by Orbit 3DM Viewer and the desktop “Map 3D (GL)”.
3DTiles Resource Configurations
Upon first opening Orbit, a <root file name>.ini and <root file name>.ord file will be created next to the <root file name>.3dtiles resource reference file.
Scaling and Translation
this <root file name>.ini file enables configuration of scaling and translation. The scale is by default set to 1 and translation is set to 0 in all three directions (x,y and z).
Geometric error
A 3D Tiles dataset consists of multiple nodes (data groups) organized into a 3D spatial tree structure. The root node of this tree defines the top level entry point for visualizing the tile dataset. When zooming in, the root node is checked to see if it needs to split to increase the level of detail shown on screen. This check is delicate: split a node too late and you see low quality data on screen. But split a node too soon and you spend too much time loading data that has no visual impact. It is a classic speed versus quality problem.
The parameter that controls the splitting of a node is called the “geometric error” and each node in the tree has a specific value for it. If the geometric error is large the node splits early, even from far away. The most detailed nodes (leaves) of the tree have a very small geometric error, the root node has the largest one.
Each vender of software products that create 3D Tile resources has their own way to calculate the geometric error. Some prefer rather large values, some rather low. To adjust for this variation of values the 3D Tile renderer can scale the geometric error of the nodes. Finding the right scale factor requires some experience. One way to avoid loading too much data is starting with a low scale factor (like 0.5) that avoids splitting and increasing it to add more visual quality as needed (to 1.5 for example). Avoid the temptation for perfection: going from good to excellent quality can easily double the amount of data streaming.
The value of the scale factor can be set in the <root file name>.ini file.
Open the ini file and add (or update) the following line:
geometric.error.scale.factor=0.50
The default value of the scale factor is 1.0.
For example, some scale factors and the effect on the data streaming (megabytes) for a certain view (GenMap,20200117)
| Scale Factor | Render Datasize (MB) | Download Datasize (MB) | Quality |
|---|---|---|---|
| 0.10 | 8.0 | 22.3 | poor |
| 0.25 | 24.7 | 54.9 | good |
| 0.30 | 37.4 | 71.9 | good |
| 0.40 | 45.8 | 109.0 | very good |
| 0.50 | 51.2 | 141.1 | very good |
| 1.00 | 60.3 | 218.0 | excellent |
The chosen scale factor was 0.40 for this dataset.
One approach might be to open the 3D tiles dataset with the desktop viewer and zoom to a specific position. Then drag-and-drop the tileset while changing the scale factor using notepad. Write down the render and load data sizes for each setting.