This area of rendering focuses on exterior scenes and has its specific snags, positives and negatives. It is used for rendering algorithms and procedures developed especially for this particular visualization type.

One of the main specifics is the illumination principle. Simply put, we can say that we illuminate the scene in the same way as in the real world, i.e. using the reflections of the Sun and the sky. It is direct sunshine when the sun’s rays are considered nearly parallel, producing sharp shadow with slight smear on the edges. The smear shows itself more with the growing distance from the edge of the object that casts this shadow. It is approximately 1 cm to 1 m distance. The Sun’s rays that refract by the atmosphere then create an extra light effect, so called Sky light, additionally illuminating the places of the scene, which are not lit by the direct sunshine.

From the model viewpoint, it can be said that when rendering exteriors and buildings, we work with much more complex scenes that are demanding on the computer memory. The reason is the common presence of the building surroundings that usually contains a large quantity of organic items, e.g. plants, rocks, natural items. When we carry out building rendering for the photorealistic visualization, we need to use various helping and simplifying techniques and use proxy objects which are more friendly to memory usage. The grass areas and a technique used for its creation are the frequently-mentioned problem.