You can download the raw 3D models in OBJ format. Besides, you can convert the OBJ files into other formats by using the Offline Format Converter in Altizure Desktop. Please find the tutorial for Format Converter here.

The formats that you can convert the OBJ files into include PLY, OSGB, KML, DAE, STL, orthomap, etc. You can download the free sample assets of obj files, orthomap, elevation map (DSM) and Google Earth 3D model at the bottom of this page.


Summary:

  • Can I download the assets in free projects?
  • There are a lot of OBJ files inside model.zip. Why is that? Which one is my model?
  • How do I determine which part of the model does each OBJ represent?
  • Then what about the files created by using the Merge function in Offline Format Converter?
  • How to view 3D models in OBJ format?
  • How to upload orthomap/dsm to Google Earth?
  • How to import 3D models into Google Earth?
  • The loading speed of KMZ file is very slow in Google Earth. Some tiles are even missing. What happened?
  • Why are my download assets different from the content described on this page?
  • Sample for downloadable assets

Can I download the assets in free projects?

No. However, you can convert a free project into a pro project and download the assets.


There are a lot of OBJ files inside model.zip. Why is that? Which one is my model?

Our 3D reconstruction engine is tuned to generate high quality 3D models from images. However, high quality also means huge data size and this put great pressure on lower end computers and devices when they need to handle one, for example, in transferring over internet, in editing the 3D models or in rendering and etc. To tackle the problem, we have employed a technique called level-of-detail (LOD) to systematically simplify and break down large 3D models into smaller pieces which we call tiles and organize them in a quadtree structure. This technique allows our engine to handle large scale 3D models more conveniently and offers you a greater flexibility in handling the models as you can choose a comfortable level-of-details model to work with according to your constraints and needs.

Quadtree structure:
Altizure_Downloadable_Asset_FAQ_EN.png
Example:
Altizure_Downloadable_Asset_FAQ_EN (1).png
In conclusion, each OBJ file in model.zip represents a particular tile of your model at certain level-of-detail. You can get the complete model after you have loaded all the tiles at the same level together into your software.


How do I determine which part of the model does each OBJ represent?

Every OBJ file is named with 3 numbers. Take the file “tile_1_0_16.obj” as an example. The first number (i.e. 1) represents the level-of-detail (LOD). The smaller the number, the more simplified is the model. The second and third number (i.e. 0, 16) represent its x-y location in the model respectively.

Example:
Altizure_Downloadable_Asset_FAQ_EN (2).png
Since the tiles are organized in quadtree structure, every step up in LOD will bring 4 times more number of tiles. Tile area will also shrink by 4 times and its length will shrink by half accordingly. Therefore, the step interval in second and third number will shrink by half as well. This process repeats until it reaches the highest LOD. By then each tile cannot be further broken down and we define its length as 1 unit.

Take our sample data, HKUST_CYT_Building, as an example. This dataset has highest LOD at level 5. Therefore, it has 2^5 = 32 tiles in both x and y direction at LOD5 and as such we says the model has a size of 32 times 32 unit large.

In LOD level 5, the most detail level is reached and each tile has a length of 1 unit. Therefore:
tile_5_1_0.obj is right next to tile_5_0_0.obj. The x coordinate is jumped by 1 unit.
tile_5_0_1.obj is right above tile_5_0_0.obj. The y coordinate is jumped by 1 unit.

In LOD level 4, each tile has a length of 2 unit. Therefore:
tile_4_2_0.obj is right next to tile_4_0_0.obj. The x coordinate is jumped by 2 unit.
tile_4_0_2.obj is right above tile_5_0_0.obj. The y coordinate is jumped by 2 unit.

In LOD level 3, each tile has a length of 4 unit. Therefore:
tile_3_4_0.obj is right next to tile_3_0_0.obj. The x coordinate is jumped by 4 unit.
tile_3_0_4.obj is right above tile_3_0_0.obj. The y coordinate is jumped by 4 unit.

In LOD level 2, each tile has a length of 8 unit. Therefore:
tile_2_8_0.obj is right next to tile_2_0_0.obj. The x coordinate is jumped by 8 unit.
tile_2_0_8.obj is right above tile_2_0_0.obj. The y coordinate is jumped by 8 unit.

In LOD level 1, each tile has a length of 16 unit. Therefore:
tile_1_16_0.obj is right next to tile_1_0_0.obj. The x coordinate is jumped by 16 unit.
tile_1_0_16.obj is right above tile_1_0_0.obj. The y coordinate is jumped by 16 unit.

In LOD level 0, each tile has a length of 32 unit and is as large as the model.
Therefore it has only one tile_0_0_0.obj file.


Then what about the files created by using the Merge function in Offline Format Converter?

You must first understand the quadtree structure and the OBJ file naming principle among model.zip before understanding the file generated by using the Merge function. If you set the block size as 32 (which is the default block size), the Format Converter will merely merge the OBJ files in model.zip for every 32 by 32 unit area, and then generate the merged OBJ files. You can roughly view them as a larger piece of tile. They still maintain LOD but no longer quadtree structure. The purpose of it is to offer users a more handy control over their models as they do not have to import a large number of fragmented pieces into software everytime.
Altizure_Downloadable_Asset_FAQ_EN (3).png
Altizure_Downloadable_Asset_FAQ_EN (3) (1).png
Altizure_Downloadable_Asset_FAQ_EN (5).png


How to view 3D models in OBJ format?

Here is an incomplete list of both free and professional softwares that read OBJ file:

Free:

  1. Autodesk FBX Review: Product Page

Professional:

Adob​​​​e Photoshop: Product Page
Autodesk 3Ds Max: Product Page
Autodesk Maya: Product Page
Blender (opensource): Product Page
Unity: Product Page


How to upload orthomap/dsm to Google Earth?

You can use this feature if you meet the following conditions:

  • the input images contain GPS information
  • the alignment of 3D reconstruction and GPS is successful.
    A step-by-step guide:
  1. Download Google Earth Pro here. Please download the pro version instead of the normal Google Earth. And Google Earth Pro is free at the moment.
  2. Convert your downloaded files to orthomap/dsm by using our Offline Converter in Altizure Desktop.
  3. Open Google Earth Pro.
  4. Go to File -> Import and select the downloaded tif files. Then the viewpoint will fly to the geographical location of your model. Choose scale to upload your orthomap on Google Earth Pro.

How to import 3D models into Google Earth?

You can use this feature if you meet the following conditions:

  • the input images contain GPS information
  • the alignment of 3D reconstruction and GPS is successful.

Please obtain the DAE and KML files by using our Offline Converter in Altizure Desktop. To display your 3D model, you can directly upload these files to Google Earth.

DAE files contain the geometry information of your models. By importing them, Google Earth will place your models in the current viewing location.

KML files contain additional GPS information. By importing them, Google Earth will place your models according to its GPS location.

To import them:

Open Google Earth Pro.
Go to File -> Open and select the downloaded DAE or KML files. In the following example, we imported the level_2_0_0.kml file.
Screenshot from 2016-04-21 16_44_44.png
You may notice that the models sometimes sink below the Google Earth terrain surface. This is due to the lack of altitude information in GPS. You can fix it by manually adjusting the altitude.

To adjust altitude:

  1. Expand the imported KML files in the sidebar (in left-hand side)
  2. Right click on the model icon
  3. Select “Properties” and go to “Altitude” tab
  4. Adjust the altitude to your needs and confirm

Screenshot from 2016-04-21 16_45_40.png
At the moment, we only provide kml and dae output up to level 5 because Google Earth cannot load higher resolution models in one batch.


The loading speed of KMZ file is very slow in Google Earth. Some tiles are even missing. What happened?

KMZ is in fact a zipped format. Therefore Google Earth will have to unzip it on the fly tiles are loaded. We suggest unzipping the KMZ file like a normal .zip file before importing into Google Earth. After unzipping you can import the Project_LOD.kml file.


Why are my download assets different from the content described on this page?

We are constantly improving our engine and providing more and more downloadable assets. If your project is reconstructed in an early time, the download assets in your project may not be up-to-date. In this case, please contact us by clicking the report problem button on the overview pages. We will arrange a free update to you after confirming the problem.


Sample

Below are the sample downloadable assets from Cheng Yu Tung Building and some other file formats that can be generated by Converter. Please feel free to download and test these samples. If you have any question, please contact us in the forum or support@altizure.com.

Online result:

Downloadable Asset: