Development of CAD applications as well as an increasing availability of detailed data of the terrain characteristics provides new possibilities in the road design process. 3D modeling of line and surface objects, unlike the “classic” design, has the uniqueness expressed through the amount of data being processed and the interaction of the buildings and the terrain with the existing and planned facilities. This paper presents an example of creation and usage of a relatively large DTM and route of the road. Eight alternative solutions of about 6.5 kilometers long road and its corresponding road junctions were designed and evaluated. Digital terrain model size of 2.4 x 6.6 kilometers was designed and used for testing and evaluating alternative solutions of the road. In making solutions, data from different sources and different levels of treatment was used and then included in a complete 3D model by using several CAD applications.
The paper discussed the problems of modeling a large object whose model not only had to meet the accuracy criteria but whose geometry file record size had to be acceptable in order to perform the computer processing in real time. The paper also offers an overview of detailed photorealistic visualization made for the acquired variant from the point of meeting the created model precision requirements (obtained by using vector and raster geodetic bases and their overlap) along with the met requirement of finding the criterion between the sufficient amount of details and adequately small file records. The paper presents the experience, observations and methods useful for future similar activities in the road design process as well as some features of 3D modeling that can affect the choice of the route and road junction technical elements.