High-Performance Graphics 2016

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https://diglib.eg.org/handle/10.2312/15439

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Browsing High-Performance Graphics 2016 by Subject "I.3.3 [Computer Graphics]"

Now showing 1 - 8 of 8
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    Adaptive Sampling for On-The-Fly Ray Casting of Particle-based Fluids
    (The Eurographics Association, 2016) Hochstetter, Hendrik; Orthmann, Jens; Kolb, Andreas; Ulf Assarsson and Warren Hunt
    We present a fast and accurate ray casting technique for unstructured and dynamic particle sets. Our technique focuses on efficient, high quality volume rendering of fluids for computer animation and scientific applications. Our novel adaptive sampling scheme allows to locally adjust sampling rates both along rays and in lateral direction and is driven by a user-controlled screen space error tolerance. In order to determine appropriate local sampling rates, we propose a sampling error analysis framework based on hierarchical interval arithmetic. We show that our approach leads to significant rendering speed-ups with controllable screen space errors. Efficient particle access is achieved using a sparse view-aligned grid which is constructed on-the-fly without any pre-processing.
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    Bandwidth-Efficient BVH Layout for Incremental Hardware Traversal
    (The Eurographics Association, 2016) Liktor, Gabor; Vaidyanathan, Karthik; Ulf Assarsson and Warren Hunt
    The memory footprint of bounding volume hierarchies (BVHs) can be significantly reduced using incremental encoding, which enables the coarse quantization of bounding volumes. However, this compression alone does not necessarily yield a comparable improvement in memory bandwidth. While the bounding volumes of the BVH nodes can be aggressively quantized, the size of the child node pointers remains a significant overhead. Moreover, as BVH nodes become comparably small to practical cache line sizes, the BVH is cached less efficiently. In this paper we introduce a novel memory layout and node addressing scheme and map it to a system architecture for fixed-function ray traversal. We evaluate this scheme using an architecture simulator and demonstrate a significant reduction in memory bandwidth, compared to previous approaches.
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    DIRT: Deferred Image-based Ray Tracing
    (The Eurographics Association, 2016) Vardis, Konstantinos; Vasilakis, Andreas-Alexandros; Papaioannou, Georgios; Ulf Assarsson and Warren Hunt
    We introduce a novel approach to image-space ray tracing ideally suited for the photorealistic synthesis of fully dynamic environments at interactive frame rates. Our method, designed entirely on the rasterization pipeline, alters the acceleration data structure construction from a per-fragment to a per-primitive basis in order to simultaneously support three important, generally conflicting in prior art, objectives: fast construction times, analytic intersection tests and reduced memory requirements. In every frame, our algorithm operates in two stages: A compact representation of the scene geometry is built based on primitive linked-lists, followed by a traversal step that decouples the ray-primitive intersection tests from the illumination calculations; a process inspired by deferred rendering and the path integral formulation of light transport. Efficient empty space skipping is achieved by exploiting several culling optimizations both in xy- and z-space, such as pixel frustum clipping, depth subdivision and lossless buffer down-scaling. An extensive experimental study is finally offered showing that our method advances the area of image-based ray tracing under the constraints posed by arbitrarily complex and animated scenarios.
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    Efficient Stackless Hierarchy Traversal on GPUs with Backtracking in Constant Time
    (The Eurographics Association, 2016) Binder, Nikolaus; Keller, Alexander; Ulf Assarsson and Warren Hunt
    The fastest acceleration schemes for ray tracing rely on traversing a bounding volume hierarchy (BVH) for efficient culling and use backtracking, which in the worst case may expose cost proportional to the depth of the hierarchy in either time or state memory. We show that the next node in such a traversal actually can be determined in constant time and state memory. In fact, our newly proposed parallel software implementation requires only a few modifications of existing traversal methods and outperforms the fastest stack-based algorithms on GPUs. In addition, it reduces memory access during traversal, making it a very attractive building block for ray tracing hardware.
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    Filtering Distributions of Normals for Shading Antialiasing
    (The Eurographics Association, 2016) Kaplanyan, Anton S.; Hill, Stephen; Patney, Anjul; Lefohn, Aaron; Ulf Assarsson and Warren Hunt
    High-frequency illumination effects, such as highly glossy highlights on curved surfaces, are challenging to render in a stable manner. Such features can be much smaller than the area of a pixel and carry a high amount of energy due to high reflectance. These highlights are challenging to render in both offline rendering, where they require many samples and an outliers filter, and in real-time graphics, where they cause a significant amount of aliasing given the small budget of shading samples per pixel. In this paper, we propose a method for filtering the main source of highly glossy highlights in microfacet materials: the Normal Distribution Function (NDF). We provide a practical solution applicable for real-time rendering by employing recent advances in light transport for estimating the filtering region from various effects (such as pixel footprint) directly in the parallel-plane half-vector domain (also known as the slope domain), followed by filtering the NDF over this region. Our real-time method is GPU-friendly, temporally stable, and compatible with deferred shading, normal maps, as well as with filtering methods for normal maps.
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    Masked Software Occlusion Culling
    (The Eurographics Association, 2016) Hasselgren, Jon; Andersson, Magnus; Akenine-Möller, Tomas; Ulf Assarsson and Warren Hunt
    Efficient occlusion culling in dynamic scenes is a very important topic to the game and real-time graphics community in order to accelerate rendering. We present a novel algorithm inspired by recent advances in depth culling for graphics hardware, but adapted and optimized for SIMD-capable CPUs. Our algorithm has very low memory overhead and is 3 faster than previous work, while culling 98% of all triangles culled by a full resolution depth buffer approach. It supports interleaving occluder rasterization and occlusion queries without penalty, making it easy to use in scene graph traversal or rendering code.
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    Photon Splatting Using a View-Sample Cluster Hierarchy
    (The Eurographics Association, 2016) Moreau, Pierre; Sintorn, Erik; Kämpe, Viktor; Assarsson, Ulf; Doggett, Michael; Ulf Assarsson and Warren Hunt
    Splatting photons onto primary view samples, rather than gathering from a photon acceleration structure, can be a more efficient approach to evaluating the photon-density estimate in interactive applications, where the number of photons is often low compared to the number of view samples. Most photon splatting approaches struggle with large photon radii or high resolutions due to overdraw and insufficient culling. In this paper, we show how dynamic real-time diffuse interreflection can be achieved by using a full 3D acceleration structure built over the view samples and then splatting photons onto the view samples by traversing this data structure. Full dynamic lighting and scenes are possible by tracing and splatting photons, and rebuilding the acceleration structure every frame. We show that the number of view-sample/photon tests can be significantly reduced and suggest further culling techniques based on the normal cone of each node in the hierarchy. Finally, we present an approximate variant of our algorithm where photon traversal is stopped at a fixed level of our hierarchy, and the incoming radiance is accumulated per node and direction, rather than per view sample. This improves performance significantly with little visible degradation of quality.
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    Watertight Ray Traversal with Reduced Precision
    (The Eurographics Association, 2016) Vaidyanathan, Karthik; Akenine-Möller, Tomas; Salvi, Marco; Ulf Assarsson and Warren Hunt
    Reduced precision bounding volume hierarchies and ray traversal can significantly improve the efficiency of ray tracing through low-cost dedicated hardware. A key approach to enabling reduced precision computations during traversal is to translate the ray origin closer to the bounding volume hierarchy node after each traversal step. However, this approach precludes sharing of intersection computations between a parent node and its two children, which is an important optimization. In this paper, we introduce a novel traversal algorithm that addresses this limitation and achieves a significant reduction in the computational complexity of traversal compared to previous approaches.We also include an analysis that shows how our algorithm guarantees watertight intersections which is a key requirement for robust image quality, especially with reduced precision traversal where numerical errors can be large.