Research And Implementation Of Illumination Technology In The 3D GIS Visualization

The realistic simulation of illumination effects is always a high-profile issues in the Three-dimensional visualization of geographic information system, is also the basic problem of computer graphics. The illumination and dynamic display of the three-dimensional terrain model is not only providing with the technologies and measures of observing the terrain model vividly and dynamically on computer for people, but also making the terrain model which is clearly in pattern and rich of information reveal in front of us. So that our understanding of the study in the region terrain pattern is more comprehensive rapid and detailed than ever before.This paper focus on describing the lighting model of the two models, local reflection models and global illumination model, research the sub-model of the two model and its applications and the derivation process, and add the application of the shadow in the global illumination model, add the rendering of light and shade in the local reflection model, achieve the combination of shadows with shading and the local reflection model with the global illumination model.In the calculation of the shadow, paper research from the shadows of the nature and the simple ground plane from the shadow, made a variety of shadow algorithm detailed understanding and in-depth study, detailed implementation of each algorithm and the application process. And made a detailed explanation of the ray tracing algorithm which is used in the paper, this algorithm is achieved in the global illumination model, and add the hidden surface elimination algorithm, the two algorithms combine in the global illumination model, and extended to the solution of the shadow completed the drawing of the shadow.In the part of the shading, and made a more comprehensive understanding and research to the previous classic way to the shading, by comparing the difference between the algorithms obtained the advantages and disadvantages of the calculation of light and shade. In the paper uses a combination of both methods not only solve the problem of efficiency but also on the effect guaranteed. On the treatment of the shading and shadows, it can be seen that in the light model can combine shadow with shade by some method, and the different models can be combined to achieve this.