Interactive Ray-Traced Area Lighting with Adaptive Polynomial Filtering

Area lighting computation is a key component for synthesizing photorealistic rendered images, and it simulates plausible soft shadows by considering geometric relationships between area lights and three-dimensional scenes, in some cases even accounting for physically-based material properties [2]. In rendering, computing visibility on a surface point can be naturally performed by a ray casting process, e.g,. processing shadow rays. However, this process typically requires a large number of shadow rays to accurately simulate penumbra regions. Otherwise, the rendered shadows can be often corrupted by a high variance, i.e., noise. This makes fully ray traced approaches non-practical under real-time constraint scenarios [1]. To tackle this problem, while achieving high-quality shadows interactively, we propose a filtering based visibility computation framework. Our method employs ray casting to accurately compute the visibility value of each sample, but we use only small sample counts to lower the sampling time required. This visibility image, generated by a small number of samples, is corrupted by high-frequency noise especially in penumbra areas. Instead of increasing the sample count, we apply our new filtering to reduce the noise and enable a high-quality rendering with soft shadows. In this short paper we present an efficient hybrid area light computation framework that uses ray casting with a small number of shadow samples to get smooth visibility maps using an adaptive post-processing filter. In the end the result of direct lighting computed using the rasterization pipeline is combined with the filtered ray-traced visibility to create the final images. Next, we provide the overview of our rendering framework devised to accelerate the visibility computations, and describe a new postprocessing filter for producing high-quality soft shadows. In addition, we demonstrate that our method generates high-quality rendering results interactively, guided by our area lighting computation that runs in real-time.