SIX DEGREES OF SIMULATION.(Technology Information)

ARCHITECTS AND ENGINEERS TURN TO VISUALIZATION TO PREDICT SIX KEY ASPECTS OF BUILDING BEHAVIOR

In architecture, engineering, and construction (AEC), every building is its own prototype, a one-off, an original. This approach places high value on analytical tools that enable designers to simulate and visualize the behavior of a proposed structure under varying conditions. Prescriptive building codes provide static formulas that regulate passive aspects of building performance, such as structural "dead loads" or thermal insulation values. However, descriptive aspects of dynamic building behavior--from lighting and acoustics to seismic and wind loads to fire resistance and escape routes--require correspondingly dynamic mathematical simulations that can best be understood through visualization.

The underlying computational techniques share several broad characteristics. Whether using radiosity (for lighting), finite element analysis (for earthquakes and vibration), or computational fluid dynamics (for smoke and flame spread), a typical analysis begins with dividing the building's surfaces, volumes, or components into small cells (squares or cubes). The analysis also assumes a uniform initial state across all divisions (for example, they are all dark, all at rest, or all at the same temperature).

Purely numerical representations of physical change can be hard to comprehend. As change is introduced into the system (light, a tremor, or heat), the effect is calculated in each immediately affected cell. Over subsequent intervals, the analysis calculates the spreading impact on adjoining cells (in the form of reflected or diffracted light, transferred structural moment, or increased temperature). A complete analysis includes not only the effects of initial cells on adjoining cells, but also the effects of those subsequent cells reflecting and affecting the previous cells.

Because the results are so difficult to interpret from numerical answers alone, architects and engineers increasingly turn to visualizations. Whether in 2D or 3D, still images or animation, such visualizations play an increasingly important role in helping to predict, identify, and correct potential trouble spots in building performance prior to construction. Indeed, as new material technologies and economic demands drive the creation of buildings that are bigger, taller, and more complex than anything contemplated by the static approach of traditional building codes, designers are growing more dependent on simulation and visualization to help ensure that their designs are safe, comfortable, and enjoyable for future inhabitants.

Seeing the Light

Architecture has been described as the manipulation of forms in light. Long before CAD models were available, architecture students and practicing professionals alike studied lighting effects by squinting at small-scale cardboard models while moving their Luxo lamps in imaginary solar arcs across a scale-model sky. Developments in computer graphics at places such as Cornell and the University of Utah allowed ever more realistic lighting and shading algorithms--from Phong to Gouraud to raytracing to radiosity--to be applied to CAD geometry. Advanced lighting simulation work at the Lawrence Berkeley National Laboratory produced Radiance, a collection of Unix routines that yields, in the hands of a skilled operator with boundless computing resources, photometrically accurate simulations of any light source in any space.