Integrating Occlusion Culling and Levels of Detail through Hardly‐Visible Sets

Occlusion culling and level‐of‐detail rendering have become two powerful tools for accelerating the handling of very large models in real‐time visualization applications. We present a framework that combines both techniques to improve rendering times. Classical occlusion culling algorithms compute potentially visible sets (PVS), which are supersets of the sets of visible polygons. The novelty of our approach is to estimate the degree of visibility of each object of the PVS using synthesized coarse occluders. This allows to arrange the objects of each PVS into several Hardly‐Visible Sets (HVS) with similar occlusion degree. According to image accuracy and frame rate requirements, HVS provide a way to avoid sending to the graphics pipeline those objects whose pixel contribution is low due to partial occlusion. The image error can be bounded by the user at navigation time. On the other hand, as HVS offer a tighter estimation of the pixel contribution for each scene object, it can be used for a more convenient selection of the level‐of‐detail at which objects are rendered. In this paper, we describe the new framework technique, provide details of its implementation using a visibility octree as the chosen occlusion culling data structure and show some experimental results on the image quality.

[1]  Tomoyuki Nishita,et al.  Shading models for point and linear sources , 1985, TOGS.

[2]  Pere Brunet,et al.  The visibility octree: a data structure for 3D navigation , 1999, Comput. Graph..

[3]  Seth J. Teller,et al.  Temporally coherent conservative visibility , 1999, Comput. Geom..

[4]  Seth J. Teller,et al.  Real-time occlusion culling for models with large occluders , 1997, SI3D.

[5]  Carlos Andújar,et al.  LOD visibility culling and occluder synthesis , 2000, Comput. Aided Des..

[6]  Enrico Gobbetti,et al.  Time-critical multiresolution scene rendering , 1999, Proceedings Visualization '99 (Cat. No.99CB37067).

[7]  Carlo H. Séquin,et al.  Adaptive display algorithm for interactive frame rates during visualization of complex virtual environments , 1993, SIGGRAPH.

[8]  Dinesh Manocha,et al.  Visibility culling using hierarchical occlusion maps , 1997, SIGGRAPH.

[9]  Dinesh Manocha,et al.  Accelerated occlusion culling using shadow frusta , 1997, SCG '97.

[10]  Daniel Cohen-Or,et al.  Conservative Visibility and Strong Occlusion for Viewspace Partitioning of Densely Occluded Scenes , 1998, Comput. Graph. Forum.

[11]  Cláudio T. Silva,et al.  Rendering on a budget: a framework for time-critical rendering , 1999, Proceedings Visualization '99 (Cat. No.99CB37067).

[12]  A. P. Brunet,et al.  Octree-based Simplifications of Polyhedral Solids , 1999 .

[13]  Pere Brunet Crosa,et al.  Data structures and algorithms for navigation in highly polygon-populated scenes , 1998 .

[14]  Paolo Cignoni,et al.  A comparison of mesh simplification algorithms , 1998, Comput. Graph..

[15]  László Neumann,et al.  Perception Based Color Image Difference , 1998, Comput. Graph. Forum.

[16]  S. Coorg,et al.  A Spacially and Temporally Coherent Object Space Visibility Algorithm , 1996 .