Jiří Bittner

Coherent Hierarchical Culling: Hardware Occlusion Queries Made Useful

We present a simple but powerful algorithm for optimizing the usage of hardware occlusion queries in arbitrary complex scenes. Our method minimizes the number of issued queries and reduces the delays due to the latency of query results. We reuse the results of occlusion queries from the last frame in order to initiate and schedule the queries in the next frame. This is done by processing nodes of a spatial hierarchy in a front‐to‐back order and interleaving occlusion queries with rendering of certain previously visible nodes. The proposed scheduling of the queries makes use of spatial and temporal coherence of visibility. Despite its simplicity, the algorithm achieves good culling efficiency for scenes of various types. The implementation of the algorithm is straightforward and it can be easily integrated in existing real‐time rendering packages based on common hierarchical data structures.

Hierarchical visibility culling with occlusion trees

In the scope of rendering complex models with high depth complexity, it is of great importance to design output-sensitive algorithms, i.e., algorithms with the time complexity proportional to the number of visible graphic primitives in the resulting image. In this paper an algorithm allowing efficient culling of the invisible portion of the rendered model is presented. Our approach uses a spatial hierarchy to represent the topology of the model. For a current viewpoint a set of polygonal occluders is determined that are used to build the occlusion tree. In the occlusion tree occlusion volumes of the selected occluders are merged. Visibility from the viewpoint is determined by processing the spatial hierarchy and classifying the visibility of its regions. In this process the occlusion tree is used to determine the viewpoint-to-region visibility efficiently. The algorithm is well-suited for complex models where large occluders are present.

CHC++: Coherent Hierarchical Culling Revisited

We present a new algorithm for efficient occlusion culling using hardware occlusion queries. The algorithm significantly improves on previous techniques by making better use of temporal and spatial coherence of visibility. This is achieved by using adaptive visibility prediction and query batching. As a result of the new optimizations the number of issued occlusion queries and the number of rendering state changes are significantly reduced. We also propose a simple method for determining tighter bounding volumes for occlusion queries and a method which further reduces the pipeline stalls. The proposed method provides up to an order of magnitude speedup over the previous state of the art. The new technique is simple to implement, does not rely on hardware calibration and integrates well with modern game engines.

Fast Insertion-Based Optimization of Bounding Volume Hierarchies

We present an algorithm for fast optimization of bounding volume hierarchies (BVH) for efficient ray tracing. We perform selective updates of the hierarchy driven by the cost model derived from the surface area heuristic. In each step, the algorithm updates a fraction of the hierarchy nodes to minimize the overall hierarchy cost. The updates are realized by simple operations on the tree nodes: removal, search and insertion. Our method can quickly reduce the cost of the hierarchy constructed by the traditional techniques, such as the surface area heuristic. We evaluate the properties of the proposed method on fourteen test scenes of different complexity including individual objects and architectural scenes. The results show that our method can improve a BVH initially constructed with the surface area heuristic by up to 27% and a BVH constructed with the spatial median split by up to 88%.

Adaptive global visibility sampling

In this paper we propose a global visibility algorithm which computes from-region visibility for all view cells simultaneously in a progressive manner. We cast rays to sample visibility interactions and use the information carried by a ray for all view cells it intersects. The main contribution of the paper is a set of adaptive sampling strategies based on ray mutations that exploit the spatial coherence of visibility. Our method achieves more than an order of magnitude speedup compared to per-view cell sampling. This provides a practical solution to visibility preprocessing and also enables a new type of interactive visibility analysis application, where it is possible to quickly inspect and modify a coarse global visibility solution that is constantly refined.

Fast robust BSP tree traversal algorithm for ray tracing

An orthogonal BSP (binary space partitioning) tree is a commonly used spatial subdivision data structure for ray-tracing acceleration. While the construction of a BSP tree takes a relatively short time, the efficiency of a traversal algorithm significantly influences the overall rendering time. We propose a new fast traversal algorithm based on statistical evaluation of all possible cases occuring during the traversal of a BSP tree. More frequent cases are handled simply, while less frequent ones are more computationally expensive. The proposed traversal algorithm handles all singularities correctly, and saves between 30% and 50% of traversal time compared with the commonly-known Sung and Arvo algorithms.

Delivering interactivity to complex tone mapping operators

The accurate display of high dynamic range images requires the application of complex tone mapping operators. These operators are computationally costly, which prevents their usage in interactive applications. We propose a general framework that delivers interactive performance to an important subclass of tone mapping operators, namely global tone mapping operators. The proposed framework consists of four steps: sampling the input image, applying the tone mapping operator, fitting the point-sampled tone mapping curve, and reconstructing the tone mapping curve for all pixels of the input image. We show how to make use of recent graphics hardware while keeping the advantage of generality by performing tone mapping in software. We demonstrate the capabilities of our method by accelerating several common global tone mapping operators and integrating the operators in a real-time rendering application.

Layout-aware optimization for interactive labeling of 3D models

We propose a novel method for computing labeling of 3D illustrations in real-time. We solve a multiple criteria optimization problem in which we consider the desired layout already in the stage of searching for salient points of the labeled areas. In the solution we employ fuzzy logic combined with greedy optimization. The method runs on the GPU and achieves interactive rates on medium sized models. The results indicate that the method compares favorably to the state-of-the-art interactive labeling techniques. Graphical AbstractWe propose a novel method for computing labeling of 3D illustrations in real-time on the GPU based on fuzzy logic and greedy optimization. Display Omitted Research Highlights? Optimized interactive labeling of 3D models. ? Solved by multiple criteria optimization using fuzzy logic. ? ? Runs on the GPU at interactive rates for medium sized models.

RDH: ray distribution heuristics for construction of spatial data structures

Surface area heuristics is currently the most popular method for view independent construction of spatial hierarchies for ray tracing. We present a method which modifies the surface area heuristics by taking into account the actual distribution of rays in the scene. This is achieved by subsampling the rays to be cast and using these rays in order to estimate the probabilities of rays traversing through nodes of the constructed hierarchy. The main aim of our paper is to analyze the potential of taking the ray distribution into account. The results indicate that we can achieve a minor speedup of ray traversal compared to standard SAH. For large densely occluded scene we can also save the construction time and memory consumption of the hierarchy by not subdividing parts of the scene where no rays are traced.

Exact regional visibility using line space partitioning

Abstract We present a new method for computing visibility from a polygonal region in the plane considering a set of line segments as occluders. The proposed method provides a comprehensive description of visibility from the given region. We represent sets of occluded rays using a hierarchical partitioning of dual space (line space). The line space partitioning is maintained by a BSP tree that provides efficient operations on the sets of lines. The implementation shows that the method is suitable for computing potentially visible sets in large scenes with various visibility characteristics.