Using AutoDesk Design Review

For Round Tripping Geotechnical 3D Models in Distributed Work Groups

This article highlights, from an applied geologist’s point of view, some benefits of using Design Review in multidisciplinary (geo*) projects, where this software can be used as an efficient tool for communicating, reviewing and fine tuning geological and geotechnical 3D models.

By Robert Marschallinger

Figure 1. 3D model of building project with prognosed geology, planned geotechnical
measures and subsurface infrastructure.

In talking about computer processing of geological and geotechnical data, the focus is on 3D models. In geotechnical projects, the goal is to design and link 3D models of geological objects (e.g., rock bodies, sediment beds etc.) and existing or planned man-made objects (e.g., galleries, caverns). Typical geotechnical projects are multidisciplinary. Just consider a traffic infrastructure building project: to support cost-efficient construction, surveyors, geologists, civil engineers, landscape planners and the contractor must cooperate closely. Minimizing the time spent in lengthy, and sometimes inefficient, team meetings, data round tripping is a widespread tool for continuously keeping track of a project. Involved data is inherently 3D-georeferenced, with CAD a key technology and AutoDesk’s dwg format a quasi standard. As the disciplines noted above work increasingly with solid models, involved data amounts tend to get huge. Even with steadily rising internet bandwidths, some handy data format which supports communicating the 3D models of surveyors, geologists and tunnel designers among all project partners is wanted. At this point, the drawing web format (DWF) and Design Review (ADR), both by AutoDesk, come in. On the one hand, DWF files, which can be easily exported from most AutoDesk software, are highly compressed containers for 2D drawings, 3D designs and related redlining information. Design Review, on the other hand, provides tools to view, review, print, and republish DWF files without the need for a CAD system.

Figure 2. Geological 3D model – partially exploded view with rock bodies
and hazardous fault system.

Since ADR strives to serve as a general DWF reviewing tool for 2D and 3D designs, a wide range of user demands has to be met. Clearly, reviewing and data round trip processes in mechanical design are different from those in architectural or civil engineering design. To prevent an associated excessive look-and-feel to the ADR user interface, only a subset of control elements is available at a time, reflecting the specific features of the DWF authoring software. For example, different user interface elements are activated depending on whether the DWF file has been output from AutoCAD (general CAD design), AutoDesk Inventor (mechanical design) or AutoDesk Map3D (CAD/GIS integration).

Here, I will briefly outline some of the ADR user interface components which will be touched on in the discussion which follows. Besides the Menu, ADR has three major window elements: the Canvas Pane – pink outline in Figure 1; the Navigator Pane – green outline; and the Toolbar Area – light blue outline. The Canvas Pane displays 2D and 3D designs, images, and animations. The Navigator Pane lets you locate related data, such as Markups, published or saved Views, Animations, Cross Sections, Layers, and Properties. Information in the Navigator Pane is grouped in Palettes. Palette entries are synchronized with the design on the Canvas Pane, i.e., selecting objects in the Canvas Pane will highlight the corresponding Palette entries and vice versa. Once objects are selected (highlighted), ADR operations can be performed on them, e.g., hiding, moving, slicing objects or editing Markups. The Model Palette gives you feedback concerning the graphical status of all objects in the 3D model: in Figure 1, several objects are switched off or rendered transparently. Since the corresponding Model Palette entry icons are presented in different colors, even the status of objects which are currently invisible on the Canvas Pane is indicated. This is helpful when navigating in more complex 3D models with many objects. Overlaid on the Canvas pane, the Steering Wheel (yellow outline in Figure 1) is a novel graphical interface that bundles the most important viewing and 3D navigating functions in the form of a transparent control area that follows the mouse pointer on the Canvas Pane. Different flavors of Steering Wheel are available from the Menu, tailored to the demands of several user groups. The Axis Tripod (Figure 2) is an interactive 3D position handler which is aimed at the rapid definition of cross sections and at the creation of exploded views of complex 3D assemblies. When such an operation is engaged, the Axis Tripod icon is overlaid on the selected object. It acts as an intelligent sensor providing intuitive object translation and rotation in 3D space.

Viewing, Viewing, Viewing …

Reviewing 3D design data critically depends on an efficient visual interface that permits, on a 2D screen, intuitive navigation in virtual 3D worlds -- in fact, the human visual cortex is the most effective interface to 3D computer modeling. This is especially true for 3D models comprising geological objects like folded or faulted strata and associated technical objects like galleries or caverns (there’s a myth that the best geologist is the one who’s seen most …). Besides viewing 3D models from standard positions (like top, front, …) or from positions exported from the DWF authoring software, ADR enables reviewers to have an interactive look from any position. The related Pan, Zoom, Orbit and Turntable functions are available from the Menu, from the Standard Toolbar, from the Context Menu and … from the Steering Wheel (hey - what’s that?). To be honest, it took me a little while to become familiar with this new feature -- I’m kind of a veteran AutoCAD user -- but applying the Steering Wheel really pays off in terms of reviewing efficiency. Much like AutoCAD’s dynamic input feature which enables on-cursor data input, working with the Steering Wheel minimizes mouse movements since options are available in place and need not be selected from the Menu or from the Toolbar. (Your boss will really be pleased to see you working even faster …). ADR allows you to save viewing configurations in the View Palette for later use.

Landscape impact of a planned quarry.

Access Granted

Apart from selective object hiding and transparency, ADR provides access to the internal geometry of complex 3D models via interactive slicing and exploded views (in DR terminology, the ‘Create Cross Section of Model’ and ‘Move and Rotate Model Parts’ buttons of the Toolbar Area). ADR Cross Sections initially parallel either the XY, XZ and YZ planes or any 3D object facet. In a next step, a Cross Section can be freely repositioned in 3D space using the Axis Tripod (Figure 2). As long as interactive re-positioning of the Cross Section plane is engaged, sliced solid objects are shown in boundary representation style, i.e., they are hollow and objects inside are visible. After the profile plane has been positioned, profiled solid objects are automatically capped, i.e., closed. Here, it is worth mentioning that ADR does not support 3Dsolids as native objects – when a DWF is exported from the authoring application, just the hulls of solid objects are transferred. A 3D model can be sliced by many Cross Sections simultaneously, and each Cross Section’s geometry is stored in the Views Palette for later re-use. While Cross Sections act upon the complete 3D model, Move and Rotate Model Parts refers to individual objects, which can be moved and rotated in 3D using the Axis Tripod. Working with geological or geotechnical 3D models, this ADR feature allows for rapid inspection of complex geological arrangements and their mutual relationships to geotechnical constructions. Figure 2 shows a geological 3D model, in which a formation has been interactively pulled out to visualize its 3D geometry. When pulling apart a 3D assembly, each step can be individually undone, or the complete sequence of object movements and rotations can be reset by selecting View>GO>Home from the menu or by pressing CTRL+G.

 
Speaker’s Corner

As outlined above, the efficiency of a data round trip to review and fine-tune 3D models critically depends on interactive tools to navigate the virtual 3D worlds. A further important component of each review process is text: feedback in a work group includes comments, questions, hints and so forth. Clearly, texts can be communicated separately from a 3D model. But enabling interactive 3D models to present textual information in place is more efficient, because a reviewer’s attention can be drawn immediately to the 3D objects of interest. Indeed, this is a specific need of computerized 3D models which has no manual counterpart! Such integrated text is called Markup in ADR. Markups consist of a text area which automatically turns to face the viewer (like a billboard node in a VRML world), and a leader line which extends from the label area to the 3D object of interest. Markups never get hidden by neighboring objects, support versioning and can be assigned predefined states in the reviewing work flow, e.g., remark, question, done. Different Markup status is indicated by colors in the Canvas Pane (see Figure 3). Besides the text, the Markup Palette in the Navigator Pane displays each Markup’s versioning data like author and date. Thus, in a round trip process, all reviewing information can be traced. Available from the Toolbar, point locations and distance measurements are stored as Markups, too. Coordinates are expressed as XYZ triples in world coordinate system units; it’s worth mentioning that the orientation of the ADR world coordinate system follows the AutoDesk Inventor convention, where Y and Z axes are exchanged with respect to the AutoCAD world coordinate system, which is standard Euclidean geometry.

Presentation

The human perception of  computerized 3D models generally increases in this order: wireframe – hidden lines – flat shaded presentation. But even with more sophisticated smooth shading algorithms, the resulting 3D models still look very technical. Of course, that’s not a problem when co-operating with trained personnel. However, laypersons and decision makers often have problems understanding these ‘compu­terized-looking’ models. Here, photorealistic rendering comes in: bitmaps - mostly photos taken from real objects - are draped over the 3D objects to make them look quasi-realistic. Texture mapping and more sophisticated methods of photorealistic visualization are meanwhile state-of-the-art in architectural design; presumably, interactive architectural walkthroughs are the main motivation for ADR to support real-time rendering of texture mapped 3D objects.

In applied geology, photorealistic rendering is widely used to communicate the impact of associa­ted landscape planning measures. When color aerial imagery is draped over triangulated digital terrain models, the landscape can be presented in a quasi-natural manner. Consider the quarry project shown in Figure 3: a solid model of the planned quarry geometry is the basis for quantitatively analyzing rock masses, tracing profile sections, communicating the 3D model to slope stability programs. Fine-tuning the 3D model can be achieved efficiently by an ADR-based round trip involving a geologist, a civil engineer, a landscape planner and the contractor. Here, in the planning group, shaded 3D models will do their job in getting various aspects and ideas across. However, that’s just one side of the coin! Convincing involved neighbors and authority representatives raising visibility and remediation issues is another problem. In such contexts, ADR excels as a flexible presentation tool. Even voluminous geological and geotechnical 3D models with texture mappings can be interactively presented to satisfy laypersons as well as decision makers.

WishList (Xmas Approaching …)

I’d be pleased to see cross sectioning of closed objects produce cappings in object color, not just in grey – this would help me to understand cross-sections easier. Hyperlinks in 3D (with the option of switching hyperink texts on/off) are a desirable feature as well as the ADR world coordinate system with axes parallel to the world coordinate system of the authoring application.

Robert Marschallinger (robert.marschallinger@oeaw.ac.at), geologist and geoinformatics consultant, is a senior scientist at the Austrian Academy of Sciences GIScience research facility in Salzburg, Austria www.oeaw-giscience.org. For more about DWF & Design Review: www.autodesk.com/dwf , www.autodesk.com/designreview.