Why is ClimateStudio so fast?

If you are accustomed to legacy lighting simulation tools, such as DIVA-for-Rhino, you may be surprised by ClimateStudio’s speed. Simulations that used to take hours can be completed in ClimateStudio in a matter of seconds. How is this possible?

ClimateStudio simulates the behavior of light using Radiance, an industry-standard, physically-based engine developed and maintained by Lawrence Berkeley National Laboratory. But unlike its predecessors, ClimateStudio implements Radiance in a progressive path tracing mode. That is, rather than tracing all possible light paths before computing a result, ClimateStudio traces a few paths at a time, updating the result as it goes.

This progressive approach lets ClimateStudio gather initial estimates almost immediately, followed by a gradual denoising of the data as light paths accumulate. Although precision increases indefinitely with additional bursts of paths (known as passes), it takes only a few passes for a reliable signal to emerge.

By combining progressive path tracing with hardware acceleration, ClimateStudio can converge on accurate results with remarkable speed. In the example below, ClimateStudio finds the Spatial Daylight Autonomy (sDA) of a sidelit office in about ten seconds. By comparison, Daysim and native Radiance take hours or days, respectively, to reach the same conclusion.

Note that the convergence around a signal is self-evident to an observer of the simulation. That is, once the result stops changing significantly from pass to pass, the observer can stop the simulation with confidence that the value is on target. She can also draw immediate conclusions from early returns. If her goal is 75% sDA, for example, she can easily see after a single pass that her design won’t reach it – and that it’s time to return to the drawing board.