| Summary: | 碩士 === 國立交通大學 === 資訊工程學系 === 86 === In dynamic environments, shadows not only improve the image
quality of the scene, but also enhance the perception of spatial
relationships. In this thesis, we purpose an object-based hard
shadow computation method for dynamic environments. First, we
attempt to find the contour (silhouette), called effective
shadowing contour (abbreviate ESC), for each object and each
point light source. The shadow volumes are constructed by the
effective shadowing contours. Next, we find occlusion
relationships between objects in the scene by some methods
similar to shadow tiling algorithm and painter's algorithm.
Finally, we use stencil buffer to generate shadows. Moreover, we
purpose speed-up methods for dynamic environments, such as local
update of scene change, normal mask for light-face/back-face
testing, frame coherence exploration for ESC computation, and
occlusion culling for reducing the number of the polygons needed
for shadow computation. According to our experiments, the
stencil buffer based method is more efficient than shadow volume
binary space partition tree (SVBSP tree) based algorithm. we
also compare three stencil buffer based methods, and try to
conclude with a suitable architecture for shadow computations.
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