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Daylight performance predictions
Published in Jan L.M. Hensen, Roberto Lamberts, Building Performance Simulation for Design and Operation, 2019
In order to accomplish both, the ability to continuously explore a scene and to get physically accurate results for a variety of materials, Nathaniel Jones tested an alternative global illumination method to analyze daylit scenes, called path tracing (Jones and Reinhart 2016). Same as light backwards raytracing, path tracing follows rays from an observer’s viewpoint backwards towards potential light sources. However, only a single ray is followed from each intersection before creating a scene visualization. The process is repeated iteratively and thus yields a succession of increasingly refined scene visualizations (Lafortune and Willems 1993). Initial results indicated that glare or daylight availability metrics derived from these intermediate images oftentimes converge quickly, providing designers with nearly immediate design feedback (Jones and Reinhart 2016).
HDR Pipeline
Published in Francesco Banterle, Alessandro Artusi, Kurt Debattista, Alan Chalmers, Advanced High Dynamic Range Imaging, 2017
Francesco Banterle, Alessandro Artusi, Kurt Debattista, Alan Chalmers
Ray tracing. Ray tracing [417] models the geometric properties of light by calculating the interactions of groups of photons, termed rays, with geometry. This technique can reproduce complex visual effects. Rays are shot from the virtual camera and traverse the scene until the closest object is hit; see Figure 2.13(a). Here the material properties of the object at that point are used to calculate the illumination, and a ray is shot toward any light sources to account for shadow visibility. The material properties at the intersection point further dictate in which direction reflected/transmitted rays need to be shot; the process is computed recursively. Due to its recursive nature, ray tracing and extensions of the basic algorithm, such as path tracing and distributed ray tracing, are naturally suited to solving the rendering equation [186], which describes the transport of light within an environment. Ray tracing methods can thus simulate effects such as shadows, reflections, refractions, indirect lighting, subsurface scattering, caustics, motion blur, indirect lighting, and others in a straightforward manner. While ray tracing is computationally expensive, recent algorithmic and hardware advances are making it possible to compute it at interactive rates for dynamic scenes [54,300].
P
Published in Phillip A. Laplante, Dictionary of Computer Science, Engineering, and Technology, 2017
path tracing an improvement on general ray-tracing techniques. Normal ray-tracing uses a constant factor to estimate the contribution of ambient light at a given surface point, but path tracing estimates the global illumination using, for example, Monte Carlo techniques. Images are thus generated using many paths through each pixel. Note that a degree of oversampling is always necessary, so this technique is computationally expensive.
Achieving realtime daylight factor computation for modular buildings in generative design
Published in Journal of Building Performance Simulation, 2022
Until ten years ago, daylighting simulations could only be fully realized on CPUs (Woop, Schmittler, and Slusallek 2005), even if functional prototypes on GPUs already existed in graphics research laboratories. The last few years have seen the democratization of deep GPU programming with architectures more adapted to ray tracing and path tracing, notably from Nvidia (CUDA-based Optix (Parker et al. 2010), RTX cards since 2019). By means of a new expertise in programming these processors, researchers have been able to obtain significant acceleration of the calculation times of many luminous quantities. It is certain that obtaining on recent GPUs computations in interactive time (currently a bit less than half a second per evaluation) opens the door to interactivity in a large number of numerical design applications, without however being considered fully as real time computation.
Effects of real-time simulation feedback on design for visual comfort
Published in Journal of Building Performance Simulation, 2019
Nathaniel L. Jones, Christoph F. Reinhart
Accelerad is a Radiance derivative created by the authors that achieves faster computational performance by running simulations in parallel on the graphics processing unit (GPU) instead of using a single central processing unit (CPU) thread (Jones and Reinhart 2014; Jones and Reinhart 2015; Jones and Reinhart 2017a). This strategy allows hours-long Radiance simulations to run in minutes through the OptiX™ ray-tracing engine (Parker et al. 2010). AcceleradRT modifies Radiance still further by using progressive path tracing (Lafortune and Willems 1993) instead of light-backwards distribution ray tracing (Cook, Porter, and Carpenter 1984). Progressive path tracing makes images at intermediate stages of rendering immediately available, reducing SRT to fractions of a second. We have previously demonstrated that progressive path tracing produces coherence in contrast ratio and DGP calculations over time, and that these results may be used with some degree of certainty starting early in the rendering process (Jones and Reinhart 2016).