Realistic rendering of environmental conditions in a construction machinery simulator applying GLSL shaders

Machinery specific simulators are designed for realistic and immersive "look and feel" of environments and behaviors of the real artifacts they resemble. But often only the "feel" component of such simulators is credible due to a lack of a realistic rendering. Current simulators use the graphic cards fixed function pipeline, and do not use the second processor unit, the Graphics Processing Unit (GPU) they have access to. Most of their high quality rendering is done by applying texture mapping techniques. In this work it is shown how to improve the rendering of specific materials and environments applying the new OpenGL shading language (GLSL) defined in the OpenGL 2.0 standard. Special attention is given to the rendering of weather conditions and soil as they contribute most to the environment perception in a construction machinery simulator, which will be the test environment of the developments shown in this work. The presented approach is implemented as part of the framework VAR-Trainer [VT05], which is an European funded Research and Development project whose main objective is the development of an advanced simulator platform for heavy construction machinery. VAR-Trainer uses the open source scene graph and renderer library OpenSG [Ope05c] that is based on OpenGL. Two methods for rendering a scene are implemented in this work: shader-based and texture mapping techniques. Using the two methods the assumption that a higher level of realism is gained using shaders is evaluated and a perception and importance metric is developed. The result for a construction site scenario is that soil and atmospheric effects are the most relevant visual effects to be included , followed by rain and clouds rendering, whereas the rendering of a realistic sky could be neglected, if, for instance, general performance criteria have to be considered.