Shadow and sky color rendering technique in augmented reality environments

Abstract

Realistic rendering technique of outdoor Augmented Reality (AR) has been an attractive topic since last two decades due to the large number of publications in computer graphics. Realistic virtual objects in outdoor rendering AR systems require sophisticated effects such as shadows, daylight and interaction between skycolor and virtual as well as real objects. A few realistic rendering techniques have been proposed to overcome this issue most of which are related to non real-time rendering. However, this problem still persists especially in outdoor rendering. This research proposed a new technique to achieve realistic real-time outdoor rendering taking into account the interaction between sky color and objects in AR systems with respect to shadows in any specific location, date and time. This approach involved four main phases, which cover different outdoor AR rendering requirements. In the first phase, sky color was generated with respect to the sun position. The second phase involved the shadow generation algorithm which is called Hybrid Shadow Mapping (HSM). During this phase some improvements in shadow volume and projection shadow are employed. The third phase started with the introduction of a coherent formula for the sun position and shadows in any specific location, date and time. The coherent formula aims to find the shadow positioning automatically. This phase also addressed the interaction between sky color and objects in virtual environments. Finally, a technique to integrate sky color and shadows through the effects of sky color on virtual objects in the AR system is proposed. The experimental results reveal that the proposed technique has significantly improved the realism of real-time outdoor AR rendering thus solving the problem of realistic AR systems.