Chapter OneFiles and File Types
Chapter 1, "Getting to Know Autodesk Navisworks," introduced you to the basics of the Autodesk Navisworks interface. In this chapter, we'll cover the principles of the various file types and the process of aggregating these disparate files together to create a single whole-project view of your model. By bringing together geometry and data from multidisciplinary teams, you can explore and review complex models in real time.
One of the most important things you can do to become proficient at Navisworks is get a firm grasp on file types and the process of how they are aggregated. File aggregation is one of the core strengths of Navisworks and one that is the foundation for all the features you'll discover in the following chapters. After all, this is how you bring your project together. Spend some time with these concepts and you'll be far more successful!
In this chapter, you'll learn to:
* Understand Navisworks file formats * Open and append various files * Configure object enablers
Navisworks File Types
The power of Navisworks rests in its ability to open files originated from a variety of design and engineering applications and its capacity to then share and coordinate these different file types into a single data-rich intelligent model. The composite model of aggregated files can then be selectively available or viewed by all parties involved to enhance the design review and coordination process. In addition, Navisworks converts and compresses most files up to 80 percent of their original size, so sharing and collaborating is greatly improved. This section will cover the numerous file types and explain the differences. We will also explore some of the standard workflows and provide best practices for file sharing and aggregation.
Native File Formats
Navisworks utilizes three native file formats: NWD, NWC, and NWF. This section will explain the differences and explore some of the various workflows.
NWD File Format
An NWD, or Navisworks Document file, is the basic file format that contains all geometry, relevant object properties, and clash tests, as well as any markup, comments, and viewpoint information. As the project evolves, an NWD can be thought of as a snapshot of the model that captures the current conditions or milestone events. This also includes clash tests and 4D simulations, which will be covered in subsequent chapters. The file size of most NWDs is considerably smaller compared to the corresponding CAD format.
NWC File Format
NWC, or Navisworks Cache files, are generated when CAD files or laser scans are opened, merged, or appended in Navisworks. They can also be created by using a designated file exporter, which we'll cover later in the section "File Exporters." NWC files are read-only files and can be thought of as a transfer mechanism to convert CAD, Autodesk Revit, and other model data into a format that Navisworks recognizes. All geometry, relevant object property information, and display settings from the original source files will carry over with the NWC export. Once the file is opened in Navisworks, any changes made—such as redlines, markups, viewpoints, or display overrides—cannot be saved back to this format.
When the native CAD format file is first brought in, Navisworks creates a file with the same name but with the .nwc file extension in the same directory as the original source file. This is an important concept of a successful Navisworks project, so keep in mind that good model management skills make this process easier.
When NWC files are opened, merged, or appended, Navisworks compares the original data to the newly created NWC file and re-caches the file if data in the original file is newer than the NWC. This ensures that as changes are made to the project design, they are reflected in your Navisworks project. If no changes are detected, Navisworks opens from the original NWC file, resulting in quicker loading. As a best practice, consider standardizing on using the Append command instead of Open. Doing so reinforces this concept of file aggregation, which is an important part of the overall project coordination process.
NWF File Format
NWF files host no 3D geometry but rather contain links to the geometry from the original native source files (see Figure 2.1). Besides the links, NWF files contain such items as markup data, viewpoints, comments, graphical overrides, search/selection sets, TimeLiner, and Clash Detective data. We'll explore these topics in more detail in future chapters.
When working with the NWF file format, you'll notice the file size for NWFs is extremely small as compared to the NWC/NWD formats; however, remember the user must have access to the original source files to view properly. As you work toward mastery of Navisworks, consider using the NWF as the standard file format during your project. While NWD files can be thought of static snapshots that capture specific milestones, using the NWF workflow is dynamic and allows for easy updating of design changes from the original source files. Later in the book, you'll explore clash detection, 4D simulation, and other concepts, so having a good grasp of the file formats is crucial.
Using NWF and NWD Formats in a Typical Workflow
Typical Navisworks workflows utilize a combination of NWD, NWC, and NWF files. As a best practice, it's recommended that during an ongoing project the NWF file format be utilized so that the original source files can be updated and re-cached. Remember, the NWF format is strictly a container that links out to the different source files. Graphical overrides such as changing model element colors and transparency are captured and stored in the NWF file. As a result, when updated cache files are loaded, Navisworks will remember your graphical settings and apply them to the updated files. This principle is similar to the concept of external references (Xrefs) in AutoCAD whereas changes made to the original source files will update the NWF file.
Similar to the NWC format, the NWD format includes all geometry and object property data but can save changes and graphical overrides to the model. The primary difference is that NWD files do not update or re-cache if changes have been made to the original source data. Sometimes having a static representation of your model is useful if you need to archive specific milestone events. Also, since this format has all of the geometry "baked" into the file, it is a perfect format to share with other users without worrying about supplying the accompanying source files.
Now that we've covered the basic file formats, let's look at a typical workflow. The project coordinator opens Navisworks and appends the original source 3D data files from the specific trades on the project (e.g., Architecture, MEP, Structure, Civil, or Existing Conditions). Navisworks converts these files to the NWC format and places the NWC files in the same directory as the original source files. Note that certain files types such as Revit (RVT) cannot be appended directly in Navisworks but must be converted to an NWC file first. This concept will be covered in the section "File Exporters" later in this chapter.
When the project coordinator saves the Navisworks session, the project is saved as an NWF format, which captures the link to the saved source and NWC files. In the meantime, the architect, MEP coordinator, structural engineer, and civil engineer all make changes, such as moving objects or adding/removing components, to their original 3D data files. When the project coordinator opens the project saved as an NWF, Navisworks will look for the linked files and do a quick comparison to determine if any of the original 3D data files are newer than the NWC files. In our sample workflow, all of these original data sources were modified, so Navisworks re-caches those files and overwrites the original NWC files with the new data. Periodically the project coordinator will save or publish the model to the NWD file format to archive specific milestone events or share with external users who do not have access to the original source data files (see Figure 2.2).
In the event the original source files are renamed or moved, Navisworks prompts you for their location, as shown in Figure 2.3. If the accompanying NWC files are moved or deleted, Navisworks automatically re-caches the files and creates a new NWC file.
To manually locate the original data source files, click the Browse button and navigate to the new location. When the NWF file is resaved, it will remember the new location for these files. Also, it should be noted that Navisworks uses a relative path structure when saving files. If your project folder contains several subfolders for the various disciplines (Architect, MEP Engineer, Structural Engineer, etc.), you can share this project folder without breaking any of the links.
File readers allow Navisworks to open and append additional file types from a variety of design and engineering applications. When you open a 3D model in Navisworks, the appropriate file reader is loaded automatically and all model geometry and associated metadata is incorporated into your scene.
Navisworks Supported Formats
In addition to the native file formats (NWD, NWC, and NWF), Navisworks can read over 40 different 3D CAD formats, as shown in Table 2.1. Model entities contained in both 2D and 3D geometry and all associated object property data is typically supported. Being able to work with such a wide range of file formats allows Navisworks to accommodate almost every design and engineering application. Having this level of file compatibility in turn allows you to collaborate, coordinate, and communicate effectively. For a complete list of supported formats and applications, see Appendix B.
In addition to the CAD formats, Navisworks is a powerful tool for viewing laser scan files, sometimes referred to as point clouds. These files are made up of millions, even billions of geo-referenced points that typically define the surface of an object. The benefit is that existing conditions such as older building structures or civil site plans can now be captured easily and displayed inside Navisworks to compare against proposed designs. Table 2.2 lists the supported laser scan formats.
Configuring File Readers
Configuring file readers is mostly automatic, but there are times when you need to adjust settings depending on the file type. Navisworks provides a full menu for each native file reader. Options vary depending on the file utilized, but the more common file types (DWG/DXF and DGN) have a robust menu with options to configure visibility settings. Here are the basic steps:
1. To access the native file reader's menu, navigate to Global Options > File Readers. 2. In the Options Editor, expand the File Readers hierarchy on the left, as shown in Figure 2.4. 3. Select the appropriate file reader and modify the settings as necessary. 4. Click OK to return to the main Navisworks application.
Since the DWG file format is one of the most recognized file reader formats in Navisworks, let's investigate these options in greater detail. The DWG/DXF file reader uses Autodesk's ObjectDBX technology, which is guaranteed to read all object geometry and information from all applications that utilize this framework. A partial snapshot of the supported object entities includes the following:
* All 2D and 3D geometry * Points and snap points * Named views * Layers * Colors * Blocks, groups, and Xrefs * Text * Attributes * Object properties
Looking at the DWG/DXG file reader, you can see a number of options that allow you to configure the settings of this file reader. Let's take a deeper look at these options:
Faceting Factor This option allows you to control the level of faceting. The default value is 1. Greater values produce smoother results, but add additional polygons and increase the file size. Max Facet Deviation This option controls the maximum distance between the facet and the actual geometry. If the distance is greater than the specified value, Navisworks adds more facets to meet this value. If the value is set to 0, this function is ignored. Split By Color Certain compound objects are displayed as one entity in Navisworks. Checking this box will split these compound objects into individual components based on their color. Examples include a door assembly that can be split into the individual door frame and door. Default Decimal Units This option specifies the type of units used to open the DWG/ DXF file.
Merge 3D Faces Occasionally some 3D models will have adjoining faces that consist of the same color, layer, and parent. This option allows Navisworks to interpret those faces as a single object. Line Processing When converting lines and polylines, Navisworks provides three options for processing them: Merge Lines By Color Navisworks will merge any lines on the same layer or proxy entity that contain the same color. This option is useful as it helps speed up navigation and overall conversion. This option is checked by default. As Provided With this option, no additional conversion takes place. All lines and polyline elements are displayed as they are specified in their native DWG file. Separate All Lines Use this option if you want to split all line elements into their respective nodes for each segment of the line. Convert Off This option allows Navisworks to convert certain layers that are switched off in the DWG file. When checked, any file that contains hidden layers will be marked as hidden in Navisworks. Convert Frozen Keeping this option checked will convert layers that are frozen in the DWG file. Any file that contains frozen layers will be marked as hidden in Navisworks when open or appended. Convert Entity Handles Keeping entity handles is an important aspect of object selection. This option will attach entity handle information to the object properties in your Navisworks model. Convert Groups This option allows you to retain your group settings in the DWG file. Files that have this option enabled gain an additional selection level in the selection tree. Convert Xrefs For those who want a seamless opening/appending of their DWG file with all Xrefs, this feature allows you to convert all reference files automatically. If left unchecked, you need to append the files manually. Merge Xrefs Layers This option allows you to merge the layers in an Xref file with the main DWG file in the selection tree. Convert Views Keep this option checked if you want to convert your named views in AutoCAD to viewpoints in Navisworks. Convert Points This option will convert all points in your DWG file. Convert Lines Select this option to convert lines and arcs in your DWG file. Convert Snap Points This option will convert snap points in your DWG file. Convert Text As its name implies, this option will convert text in your DWG file. Default Font This option allows you to define which font you want to use for the converted text. There is no predefined list for this option; rather, you need to type in the name of the font you wish to use. Convert Point Clouds DWG files that have embedded point clouds entities will only display if this box is checked. This option is separate from the laser scan/point cloud readers.
Point Cloud Detail This option allows you to specify the density of the point cloud. Values are between 1 and 100, where 100 is the maximum density. To assist with performance issues when working with larger point clouds, you might want to reduce this value to speed the conversion process.