Virtual Prototyping of Automotive Interiors

During the design of an automobile, detailed mockups of the interior are being built to study the design and evaluate human factors and ergonomic issues. These physical prototypes are expensive, time consuming, and difficult to modify.

Immersive virtual reality (VR) provides an effective alternative. A virtual prototype can replace a physical mockup for the analysis of design aspects like: layout and packaging efficiency; visibility of instruments, controls and mirrors; reachability and accessibility; clearances and collisions; human performance; aesthetics and appeal; and more. A person, placed in a seating buck, is immersed in the virtual interior and can study the design and interact with the virtual car.

A seating buck is used for immersive viewing and interactions:

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In an 1993-95 project sponsored by Chrysler Corporation, we studied the process of "Virtual Prototyping", i.e., the many steps required for the creation of a virtual representation from a CAD/CAM model and for the subsequent use of the prototype in immersive VR. We implemented a systematic approach and developed a suit of interactive tools, automatic algorithms, and data formats that cover the entire process.

The time required for the creation of a virtual prototype was reduced from several weeks or months to a few hours. This significant step towards the goal of "Rapid Virtual Prototyping" proved that the application of VR can shorten the design cycle time, reduce costs, and allow for improved market response with products that have been optimized through the study of a larger number of "virtual" design alternatives.

The steps of the virtual prototyping process can be summarized as follows:
In the following, some of these steps are briefly explained and illustrated. For additional background information refer to Virtual Reality: A Short Introduction.


The geometry of automotive interiors consists almost exclusively of curved surfaces. The given CAD/CAM model uses a mathematical representation for these free-form shapes (e.g., B-splines, NURBS, etc.). The virtual prototype, however, has to present the geometry via computer graphics primitives like points, lines, or polygons. Curved surfaces have to be approximated by polygon meshes using tessellation algorithms. Typically, large numbers of polygons are created (several millions for an interior). Decimation algorithms reduce the polygon count to a level that allows for realtime rendering response at a desired rate of 20 to 30 frames/second during immersive viewing.

Initial tessellation of a dashboard and result of polygon decimation:

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The CAD/CAM model of a surface typically consist of several trimmed surface patches that are connected along common boundaries. Tessellation and decimation of individual patches create gaps or overlaps between these patches. A stitching algorithm "sews" the disconnected patches together and creates a uniform polygon mesh with shared vertices at the patch boundaries.

Stitching along the common boundary of two surface patches:

left: common boundary - center: tessellation - right: stitching
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The modeling of elements with complex details like instruments, radio, or air-outlets requires large numbers of polygons. Texture maps are an excellent tool to reduce geometric complexity. Computer renderings or photographs of these elements are converted into bitmaps and a cut-out of the image is pasted precisely at the correct location within the virtual prototype.

A photo is converted into a texture map and placed at the correct location:

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Use of textures for other elements and for external surroundings:

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To place a person properly inside the virtual automotive interior and to allow for realistic (haptic) interactions with essential elements, a physical seating buck is used in this application. The buck consists of seat, steering wheel, foot pedals, and stick shift. The virtual interior is presented via a stereoscopic display device. A precise calibration of the virtual display with the physical elements of the seating buck is instrumental for the usefulness of the virtual prototype. When the user grabs the virtual steering wheel with the data glove controlled virtual hand, he or she must feel the physical steering wheel at the very same location.

The seating buck provides the essential physical elements, an immersive display device presents the virtual interior at a calibrated location:

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For the final use of the virtual prototype, interactions with the interior need to be defined by specifying the prototype's response to operations by the user. Functionality and behavior of the prototype is scripted in the form of event-action relations. For example, if the user touches a radio button with the data glove (event), sound will be generated (action). Touching another control may start or stop the windshield wiper. Virtual pop-up menus can be called up for the modification of interior colors, lighting environment, and other settings.

Changing the light settings via a virtual pop-up menu:

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K.-P. Beier, "Virtual Reality in Automotive Design and Manufacturing," Proceedings , Convergence '94, International Congress on Transportation Electronics, SAE (Society of Automotive Engineers), Dearborn, Michigan, October 1994.

K.-P. Beier, "Virtual Reality - Advanced Design and Manufacturing," ESD Technology , Volume 56, No. 1, pp 22-28, January 1995.

Last Update: December 7, 2002, kpb
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