How to Convert CAD Models for Use in STK

Overview of 3D models

3D models add realism to STK by depicting objects as they truly appear. While AGI has a plethora of models available, many users prefer to place their own CAD-based models in STK. To use your own model in STK, you need to convert the model to a glTF model (*.gltf, *.glb), a COLLADA model (*.dae), or an STK MDL model (*.mdl). If you are using the STK MDL model, you need to convert the CAD model to a LightWave model (*.LWO) first and then to a STK MDL model (*.mdl).

To learn more about the different model formats supported by STK, please see the STK Help for using models. 
 

Converting 3D models

To learn how to convert a model into the COLLADA format for use in STK, please see the attached tutorial. The tutorial utilizes a free 3D modeling program called Blender, which is one of many tools that you could use to convert CAD models for use in STK. 

The attached tutorial provides a walk-through of the following list of materials to convert a satellite model in STL format to COLLADA format with a full set of articulations.
 

1. Blender Fundamentals
   1. Recommended settings and basic controls
   2. Working with primitives
   3. Importing model files
2. Modifying and Preparing Models for Use in STK
   1. Component scaling
   2. Axes alignment
   3. Component alignment
   4. Component parenting
   5. Shading
   6. Solar panel groups
   7. Sensor attach points
3. Materials and Textures
   1. Adding materials and colors
   2. Adding textures with UV mapping
4. Exporting and Articulation File Creation
   1. Exporting COLLADA file
   2. Creating ancillary files
5. Implementation in STK

Every CAD conversion is different and depends on the user's requirements for the geometry and how accurate the materials need to look. Not every step in the tutorial will be necessary for each model. 
 

Best practices

Before importing the CAD model into Blender, there are a few things to consider. The biggest issue is to have the data prepared for export. Here are a few guidelines to consider:

1. Remove spaces from the names of files.
2. Remove any internal geometry; you will not be able to see it.
3. Remove all small parts such as nuts, bolts, washers, bolt holes, and wiring. They unnecessarily add to the polygon count once converted.
4. After the edits, you should save the CAD model in its native file format, using a different name, and then export it to an STL format.
5. For any parts that you plan to articulate in STK, save them as a separate file.

If you don’t have the software, you could send a request back to the CAD engineer and request the edits.

Depending on the detail of the original CAD file, the converted model file could still have so many polygons that it won't load into STK. While there is a no limit to the number of polygons your model can have, other than the hardware of your machine, there is a limit to the number of polygons per Node/Component/Layer. If the exported STL file is larger than 10MB, or roughly 90,000 polygons, then break it up into at least a couple of assemblies or it will not load into STK. The reason for this is that the XML reading library libXML used by the COLLADA DOM has a limit of 10 million characters within any XML tag.

This does not mean that you cannot have any file larger than 10MB. It only means that each component/assembly/node within the COLLADA file cannot be larger than 10MB. You can have as many components/assemblies/nodes as you need.