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Document HDA:

Typically the starting point for Onshape access. Collects all available documents by Folder, by Team or by indiviual Onshape URL. Below shows some of the attributes that are stored per pdg.WorkItem that reprent the document as well as the HDA interface.

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Expand Elements HDA:

Documents are just containers which house assembly, partstudio and blob elements. The Expand Elements HDA takes in attributes from upstream document data, gathers and breaks out all of the elements associated with the document into seperate data streams. As you can see from the below attributes list, we are building a data story by joining assembly element data with the document owner of the element.

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Get Assembly BOM & Get Assembly Definition HDAs:

Assemblies are the meat and potatoes of Onshape CAD. In order to support assembly processing in downstream applications, additional definition details are required. Both the Assembly BOM & Assembly Definition HDAs collect a large amount of definition data for the specified assembly. There is little value in showing you a brick of data visually here. I will state that the Assembly Definition data is extremely important in rebuilding the hierarchy of the CAD assembly with appropriate positionings (transformations) of all the components. The collected data is serialized as a large json string.

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Get Part Studio Body Details HDA:

Another utility HDA that retrieves a large block of detail defining a Part Studio element in Onshape. Typically, assemblies are the focus, but when the need arises to tap into a Part Studio, this utility HDA can become useful. The collected data is serialized as a large json string.

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Download Element HDA:

Handles downloading either Assembly, Part Studio or Blob elements to disk. The HDA allows for CAD to be downloaded as Parasolid or STEP while the Blob elements retain their original file extension (.pdf, .jpg, etc..).

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This suite of HDAs allows for Onshape => Houdini integration and provide excellent pipeline utility in an Onshape-centic environment. Each tool builds off the last and together they allow for great flexibility and modularity in pipeline design. The HDAs in this section are not intended to be user-facing, but used in a backend data pipeline.

LOD Profiling:

Generating LODs directly from CAD, as opposed to decimating or remodeling, achieves higher mesh integrity, saves time and increases surface accuracy. By "mixing" LODs together, I am able to get an acceptable level of optimization for real-time applications (WebGL Demo).

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Persistent Attributes:

Maintaining a close relationship between mesh LODs and the source CAD can be leveraged to make attributes persistent across LODs, as well as provide handy selection sets driven by CAD surface patch data. Assigned materials or decals to one LOD can be propogated to all other LODs.

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Non-Destructive & Pipeline Capable:

The translation workflow is very Houdini-centric, as opposed to doing heavy processing in various other upstream solutions. This is intentional as it allows Houdini access to the raw translated mesh data. By consolidating a majority of the post-translation work to Houdini, dependencies can be better managed and pipelines can be streamlined.