Abstract
The most important component of photorealism in Computer Graphics is given by a physically correct approximation of the light transport. Besides the direct illumination from light sources, there is an indirect illumination, produced by the reflections of the light rays on other surfaces of the scene. In Computer Graphics, the process of computing the illumination of a surface by considering both the direct and the indirect illumination is widely known as global illumination. This paper describes several classes of real-time global illumination techniques used in current game engines together with our own implementations of these approaches. All implementations were made in our own framework, specially designed with a multi-pass rendering architecture that allows fast implementation of rendering techniques and the reuse of functionalities. We analyze these classes based on the following criteria: the visual results produced by the indirect diffuse lighting, the ability to produce glossy reflections, shadows, ambient occlusion, subsurface scattering, translucency and volumetric lighting as well as the ability to simulate area lights. We present the quantitative results of our implementations, obtained with the same external parameters for all techniques, thanks to the unified implementations in the same framework. An important observation is that our analysis is focused on the techniques that are based on the rasterization pipeline, thus, the comparison does not include the techniques designed entirely for the ray-tracing pipeline.
Highlights
The rise of photorealism in real-time computer graphics took a big turn in recent years thanks to the advancements of the graphics processing units (GPUs)
We provide and analyze the quantitative results of our implementations concluding with our recommendations for the best scenarios that suit each class of selected real-time global illumination techniques
IMPLEMENTATION For each class of real-time global illumination techniques described in the previous section, except for the one based on ray-tracing hardware solutions, we have developed our own implementation
Summary
The rise of photorealism in real-time computer graphics took a big turn in recent years thanks to the advancements of the graphics processing units (GPUs). This built-in global illumination approach is completely precomputed It offers various implementations for real-time techniques, but the support for them is partially limited, requiring additional work for the developer. To game engines, there are several frameworks called global illumination engines, which provide only the illumination part and support integration in most of the commercially available game engines or in proprietary ones They usually offer solid implementations of pre-computed techniques but lack support for real-time ones. One such example is the framework called Enlighten [4], which uses a hybrid technique that offers partially dynamic global illumination results, but still requires a scene pre-processing pass.
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