High-Performance Graphics 2016

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

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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.
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.
GVDB: Raytracing Sparse Voxel Database Structures on the GPU
(The Eurographics Association, 2016) Hoetzlein, Rama Karl; Ulf Assarsson and Warren Hunt
Simulation and rendering of sparse volumetric data have different constraints and solutions depending on the application area. Generating precise simulations and understanding very large data are problems in scientific visualization, whereas convincing simulations and realistic visuals are challenges in motion pictures. Both require volumes with dynamic topology, very large domains, and efficient high quality rendering.We present the GPU voxel database structure, GVDB, based on the voxel database topology of Museth [Mus13], as a method for efficient GPU-based compute and raytracing on a sparse hierarchy of grids. GVDB introduces an indexed memory pooling design for dynamic topology, and a novel hierarchical traversal for efficient raytracing on the GPU. Examples are provided for ray sampling of volumetric data, rendering of isosurfaces with multiple scattering, and raytracing of level sets. We demonstrate that GVDB can give large performance improvements over CPU methods with identical quality.
Lightcut Interpolation
(The Eurographics Association, 2016) Rehfeld, Hauke; Dachsbacher, Carsten; Ulf Assarsson and Warren Hunt
Many-light rendering methods replace multi-bounce light transport with direct lighting from many virtual point light sources to allow for simple and efficient computation of global illumination. Lightcuts build a hierarchy over virtual lights, so that surface points can be shaded with a sublinear number of lights while minimizing error. However, the original algorithm needs to run on every shading point of the rendered image. It is well known that the performance of Lightcuts can be improved by exploiting the coherence between individual cuts. We propose a novel approach where we invest into the initial lightcut creation at representative cache records, and then directly interpolate the input lightcuts themselves as well as per-cluster visibility for neighboring shading points. This allows us to improve upon the performance of the original Lightcuts algorithm by a factor of 4-8 compared to an optimized GPU-implementation of Lightcuts, while introducing only a small additional approximation error. The GPU-implementation of our technique enables us to create previews of Lightcuts-based global illumination renderings.
Local Shading Coherence Extraction for SIMD-Efficient Path Tracing on CPUs
(The Eurographics Association, 2016) Áfra, Attila T.; Benthin, Carsten; Wald, Ingo; Munkberg, Jacob; Ulf Assarsson and Warren Hunt
Accelerating ray traversal on data-parallel hardware architectures has received widespread attention over the last few years, but much less research has focused on efficient shading for ray tracing. This is unfortunate since shading for many applications is the single most time consuming operation. To maximize rendering performance, it is therefore crucial to effectively use the processor's wide vector units not only for the ray traversal step itself, but also during shading. This is non-trivial as incoherent ray distributions cause control flow divergence, making high SIMD utilization difficult to maintain. In this paper, we propose a local shading coherence extraction algorithm for CPU-based path tracing that enables efficient SIMD shading. Each core independently traces and sorts small streams of rays that fit into the on-chip cache hierarchy, allowing to extract coherent ray batches requiring similar shading operations, with a very low overhead. We show that operating on small independent ray streams instead of a large global stream is sufficient to achieve high SIMD utilization in shading (90% on average) for complex scenes, while avoiding unnecessary memory traffic and synchronization. For a set of scenes with many different materials, our approach reduces the shading time with 1.9–-3.4 compared to simple structure-of-arrays (SoA) based packet shading. The total rendering speedup varies between 1.2-3 , which is also determined by the ratio of the traversal and shading times.
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.
SVGPU: Real Time 3D Rendering to Vector Graphics Formats
(The Eurographics Association, 2016) Ellis, Apollo I.; Hunt, Warren; Hart, John C.; Ulf Assarsson and Warren Hunt
We focus on the real-time realistic rendering of a 3-D scene to a 2-D vector image. There are several application domains which could benefit substantially from the compact and resolution independent intermediate format that vector graphics provides. In particular, cloud streaming services, which transmit large amounts of video data and notoriously suffer from low resolution and/or high latency. In addition, display resolutions are growing rapidly, exacerbating the issue. Raster images for large displays prove a significant bottleneck when being transported over communication networks. However the alternative of sending a full 3D scene worth of geometry is even more prohibitive. We implement a real time rendering pipeline that utilizes analytic visibility algorithms on the GPU to output a vector graphics representation of a 3D scene. Our system SVGPU (Scalable Vector on the GPU) is fast and efficient on modern hardware, and simple in design. As such we are making a much needed step towards enabling the benefits of vector graphics representations to be reaped by the real time community.

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Browsing High-Performance Graphics 2016 by Subject "I.3.7 [Computer Graphics]"

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