Research On Application Of Visibility Culling Algorithm In Dense Building Scene

With the development of movie special effects,video games,virtual city simulation and other fields,dense building scenes have begun to appear in various applications.In order to ensure its real-time rendering,visibility culling algorithms are commonly used.Among it,based on the good occlusion of the building itself,the occlusion culling algorithm can effectively reduce the amount of rendering entities and improve the rendering efficiency.Because the coherent hierarchical culling algorithm based on hardware occlusion query can not only play the characteristics of flexible,accurate,and easy-to-use of occlusion query,but also can effectively use the spatial and temporal coherence of visibility between frames to further solve its delay,reduce the number of queries and rendering state switching,which is one of the most widely used occlusion culling algorithms.On the basis of in-depth research on the principles of related space division,view-frustum culling and occlusion culling algorithms,the visibility culling algorithm based on bounding volume hierarchy was selected and implemented,including the construction of bounding volume hierarchy based on surface area heuristics,the view-frustum culling based on plane consistency principle,and the coherent hierarchical culling based on the Open GL occlusion query interface.The main improvements include:(1)Improve the test order of the frustum plane according to the rejection rate to reduce the number of plane tests.(2)Taking advantage of the good occlusion of the building itself and the principle of perspective projection,increasing the threshold of the invisible node queue to reduce the number of queries and the number of rendering state switching when large-scale objects change their visibility.(3)Taking advantage of the scene characteristics of the large difference in volume between the architectural model and the non-architectural model,unnecessary queries can be avoided by setting the area threshold to treat the model that is too small relative to the building volume as a whole.Experiments have proved that the space division method based on the surface area heuristic has a higher degree of fit to the model,and the improvements made to the scene can further reduce the amount of calculation and improve the rendering efficiency,the visibility culling algorithm built on these foundations is efficient in dense building scene..