Abstract We propose a high‐performance and compact method for computing glossy specular reflections. Commonly‐used prefiltered environment maps have large storage requirements and high error due to constrained treatment of view‐dependence. We propose a factorized spherical harmonic exponential representation that exploits new observations of the benefits of log‐space reconstruction for reflectance. Our method is compact, properly accounts for view‐dependent reflections, and is more accurate than the state‐of‐the‐industry solutions. We achieve higher quality results with an order of magnitude less memory, all with efficient and alias‐free reconstruction of glossy reflections from environment lights and continuously‐varying material roughness.

Abstract We study the problem of efficient representation of potentially high‐dimensional, spatially coherent signals in the context of precomputed light transport. We present a basis decomposition framework, Moving Basis Decomposition (MBD), that generalizes many existing basis expansion methods and enables high‐performance, seamless reconstruction of compressed data. We develop an algorithm for solving large‐scale MBD problems. We evaluate MBD against state‐of‐the‐art in a series of controlled experiments and describe a real‐world application, where MBD serves as the backbone of a scalable global illumination system powering multiple, current and upcoming 60Hz AAA‐titles running on a wide range of hardware platforms.

We describe the design and evolution of UberBake, a global illumination system developed by Activision, which supports limited lighting changes in response to certain player interactions. Instead of relying on a fully dynamic solution, we use a traditional static light baking pipeline and extend it with a small set of features that allow us to dynamically update the precomputed lighting at run-time with minimal performance and memory overhead. This means that our system works on the complete set of target hardware, ranging from high-end PCs to previous generation gaming consoles, allowing the use of lighting changes for gameplay purposes. In particular, we show how to efficiently precompute lighting changes due to individual lights being enabled and disabled and doors opening and closing. Finally, we provide a detailed performance evaluation of our system using a set of production levels and discuss how to extend its dynamic capabilities in the future.

Game and movie studios are switching to physically based rendering en masse, but physically accurate filter convolution is difficult to do quickly enough to update reflection probes in real-time. Cubemap filtering has also become a bottleneck in the content processing pipeline. We have developed a two-pass filtering algorithm that is specialized for isotropic reflection kernels, is several times faster than existing algorithms, and produces superior results. The first pass uses a quadratic b-spline recurrence that is modified for cubemaps. The second pass uses lookup tables to determine optimal sampling in terms of placement, mipmap level, and coefficients. Filtering a full 1282 cubemap on an NVIDIA GeForce GTX 980 takes between 160 µs and 730 µs with out method, depending on the desired quality.

Abstract We present several enhancements to model‐reduced fluid simulation that allow improved simulation bases and two‐way solid–fluid coupling. Specifically, we present a basis enrichment scheme that allows us to combine data‐driven or artistically derived bases with more general analytic bases derived from Laplacian eigenfunctions. We handle two‐way solid–fluid coupling in a time‐splitting fashion—we alternately timestep the fluid and rigid body simulators, while taking into account the effects of the fluid on the rigid bodies and vice versa. We employ the vortex panel method to handle solid–fluid coupling and use dynamic pressure to compute the effect of the fluid on rigid bodies. Copyright © 2014 John Wiley & Sons, Ltd.

We present several enhancements to model-reduced fluid simulation that allow improved simulation bases and two-way solid-fluid coupling. Specifically, we present a basis enrichment scheme that allows us to combine data driven or artistically derived bases with more general analytic bases derived from Laplacian Eigenfunctions. We handle two-way solid-fluid coupling in a time-splitting fashion---we alternately timestep the fluid and rigid body simulators, while taking into account the effects of the fluid on the rigid bodies and vice versa. We employ the vortex panel method to handle solid-fluid coupling and use dynamic pressure to compute the effect of the fluid on rigid bodies.

Modular Radiance Transfer (MRT) is a recent technique for computing approximate direct-to-indirect transport. Scenes are dynamically constructed by warping and connecting simple shapes and compact transport operators are only precomputed on these simple shapes. MRT ignores fine-scale transport from "clutter" objects inside the scene, and computes light transport with reduced dimensional operators, which allows extremely high performance but can lead to significant approximation error. We present several techniques to alleviate this limitation, allowing the light transport from clutter in a scene to be accounted for. We derive additional low-rank delta operators to compensate for these missing light transport paths by modeling indirect shadows and interreflections from, and onto, clutter objects in the scene. We retain MRT's scene-independent precomputation and augment its scene-dependent initialization with clutter transport generation, resulting in increased accuracy without a performance penalty. Our implementation is simple, requiring a few small matrix-vector multiplications that generate a delta lightmap added to MRT's output, and does not adversely affect the performance benefits of the overall algorithm.

This tutorial will cover the basics of physically-based rendering such as reflection models (BRDF), volume scattering (phase functions), optical phenomena (dispersion and polarization). It will also cover image formation via basic camera models. A brief summary of popular algorithms will be covered including radiosity, path tracing, photon tracing, and Metropolis Light Transport. The course will end with a more detailed description of adjoint photon tracing so that attendees can later implement their own physically-based renderer.

Abstract We investigate the representation of signals defined on triangle meshes using linearly interpolated vertex attributes. Compared to texture mapping, storing data only at vertices yields significantly lower memory overhead and less expensive runtime reconstruction. However, standard approaches to determine vertex values such as point sampling or averaging triangle samples lead to suboptimal approximations. We discuss how an optimal solution can be efficiently calculated using continuous least‐squares. In addition, we propose a regularization term that allows us to minimize gradient discontinuities and mach banding artifacts while staying close to the optimum. Our method has been integrated in a game production lighting tool and we present examples of representing signals such as ambient occlusion and precomputed radiance transfer in real game scenes, where vertex baking was used to free up resources for other game components.

We present progressive photon beams, a new algorithm for rendering complex lighting in participating media. Our technique is efficient, robust to complex light paths, and handles heterogeneous media and anisotropic scattering while provably converging to the correct solution using a bounded memory footprint. We achieve this by extending the recent photon beams variant of volumetric photon mapping. We show how to formulate a progressive radiance estimate using photon beams, providing the convergence guarantees and bounded memory usage of progressive photon mapping. Progressive photon beams can robustly handle situations that are difficult for most other algorithms, such as scenes containing participating media and specular interfaces, with realistic light sources completely enclosed by refractive and reflective materials. Our technique handles heterogeneous media and also trivially supports stochastic effects such as depth-of-field and glossy materials. Finally, we show how progressive photon beams can be implemented efficiently on the GPU as a splatting operation, making it applicable to interactive and real-time applications. These features make our technique scalable, providing the same physically-based algorithm for interactive feedback and reference-quality, unbiased solutions.

We propose a method for learning linear upsampling operators for physically-based cloth simulation, allowing us to enrich coarse meshes with mid-scale details in minimal time and memory budgets, as required in computer games. In contrast to classical subdivision schemes, our operators adapt to a specific context (e.g. a flag flapping in the wind or a skirt worn by a character), which allows them to achieve higher detail. Our method starts by pre-computing a pair of coarse and fine training simulations aligned with tracking constraints using harmonic test functions. Next, we train the upsampling operators with a new regularization method that enables us to learn mid-scale details without overfitting. We demonstrate generalizability to unseen conditions such as different wind velocities or novel character motions. Finally, we discuss how to re-introduce high frequency details not explainable by the coarse mesh alone using oscillatory modes .

Many rendering algorithms willingly sacrifice accuracy, favoring plausible shading with high-performance. Modular Radiance Transfer (MRT) models coarse-scale, distant indirect lighting effects in scene geometry that scales from high-end GPUs to low-end mobile platforms. MRT eliminates scene-dependent precomputation by storing compact transport on simple shapes, akin to bounce cards used in film production. These shapes' modular transport can be instanced, warped and connected on-the-fly to yield approximate light transport in large scenes. We introduce a prior on incident lighting distributions and perform all computations in low-dimensional subspaces. An implicit lighting environment induced from the low-rank approximations is in turn used to model secondary effects, such as volumetric transport variation, higher-order irradiance, and transport through lightfields. MRT is a new approach to precomputed lighting that uses a novel low-dimensional subspace simulation of light transport to uniquely balance the need for high-performance and portable solutions, low memory usage, and fast authoring iteration.

Obscurance and Ambient Occlusion (AO) are popular techniques in both film and games that model how ambient light is shadowed. While it is largely a solved problem for static scenes, for dynamic scenes it is still difficult to compute at interactive rates. Recent attempts to compute AO in screen space for dynamic scenes either have poor performance or suffer from under-sampling problems. We formulate the problem as a 3D volumetric integral, which maps more naturally to graphics hardware. This integral can be solved using line samples to improve the under-sampling problems that plague other techniques. Following the idea of line integrals to its logical conclusion, we show results using area samples that use a simple statistical model of the depth buffer that allows us to use a single sample. We also discuss strategies for generating point, line, and area sample patterns along with ways to incorporate the surface normal into the volume obscurance calculation.

Abstract Skinning is a simple yet popular deformation technique combining compact storage with efficient hardware accelerated rendering. While skinned meshes (such as virtual characters) are traditionally created by artists, previous work proposes algorithms to construct skinning automatically from a given vertex animation. However, these methods typically perform well only for a certain class of input sequences and often require long pre‐processing times. We present an algorithm based on iterative coordinate descent optimization which handles arbitrary animations and produces more accurate approximations than previous techniques, while using only standard linear skinning without any modifications or extensions. To overcome the computational complexity associated with the iterative optimization, we work in a suitable linear subspace (obtained by quick approximate dimensionality reduction) and take advantage of the typically very sparse vertex weights. As a result, our method requires about one or two orders of magnitude less pre‐processing time than previous methods.

Many games have used some form of lighting pre-computation to increase realism. As computational power has increased these techniques have evolved from traditional diffuse scalar radiosity, to vector irradiance formulations of radiosity that decouple normal variation to techniques that can model non-diffuse materials. This talk will cover how these techniques have been used in games over time and the outstanding research problems going forward in this area. The challenge of getting your research adopted in games, or doing research that games find interesting and relevant, will also be discussed.

Scan and segmented scan are important data-parallel primitives for a wide range of applications. We present fast, work-efficient algorithms for these primitives on graphics processing units (GPUs). We use novel data representations that map well to the GPU architecture. Our algorithms exploit shared memory to improve memory performance. We further improve the performance of our algorithms by eliminating shared-memory bank conflicts and reducing the overheads in prior shared-memory GPU algorithms. Furthermore, our algorithms are designed to work well on general data sets, including segmented arrays with arbitrary segment lengths. We also present optimizations to improve the performance of segmented scans based on the segment lengths. We implemented our algorithms on a PC with an NVIDIA GeForce 8800 GPU and compared our results with prior GPU-based algorithms. Our results indicate up to 10x higher performance over prior algorithms on input sequences with millions of elements.

We present a new, general, and real-time technique for soft global illumination in low-frequency environmental lighting. It accumulates over relatively few spherical proxies which approximate the light blocking and re-radiating effect of dynamic geometry. Soft shadows are computed by accumulating log visibility vectors for each sphere proxy as seen by each receiver point. Inter-reflections are computed by accumulating vectors representing the proxy's unshadowed radiance when illuminated by the environment. Both vectors capture low-frequency directional dependence using the spherical harmonic basis. We also present a new proxy accumulation strategy that splats each proxy to receiver pixels in image space to collect its shadowing and indirect lighting contribution. Our soft GI rendering pipeline unifies direct and indirect soft effects with a simple accumulation strategy that maps entirely to the GPU and outperforms previous vertex-based methods.

High dynamic range (HDR) images are increasingly employed in games and interactive applications for accurate rendering and illumination. One disadvantage of HDR images is their large data size; unfortunately, even though solutions have been proposed for future hardware, commodity graphics hardware today does not provide any native compression for HDR textures.

Normal mapping is a variant of bump mapping that is commonly used in computer games. It models complex surface variations by explicitly storing a surface normal in a texture map. However, it has not been used with precomputed radiance transfer (PRT), a technique for modeling an object's response to a parameterized model of lighting, which enables interactive rendering of complex global illumination effects such as soft shadows and interreflections. This paper presents several techniques that effectively combine normal mapping and precomputed radiance transfer for rigid objects. In particular, it investigates representing the convolved radiance function in various bases and borrowing concepts from the separable decomposition of BRDF's.

Previous methods for soft shadows numerically integrate over many light directions at each receiver point, testing blocker visibility in each direction. We introduce a method for real-time soft shadows in dynamic scenes illuminated by large, low-frequency light sources where such integration is impractical. Our method operates on vectors representing low-frequency visibility of blockers in the spherical harmonic basis. Blocking geometry is modeled as a set of spheres; relatively few spheres capture the low-frequency blocking effect of complicated geometry. At each receiver point, we compute the product of visibility vectors for these blocker spheres as seen from the point. Instead of computing an expensive SH product per blocker as in previous work, we perform inexpensive vector sums to accumulate the log of blocker visibility. SH exponentiation then yields the product visibility vector over all blockers. We show how the SH exponentiation required can be approximated accurately and efficiently for low-order SH, accelerating previous CPU-based methods by a factor of 10 or more, depending on blocker complexity, and allowing real-time GPU implementation.

Precomputed radiance transfer (PRT) captures realistic lighting effects from distant, low-frequency environmental lighting but has been limited to static models or precomputed sequences. We focus on PRT for local effects such as bumps, wrinkles, or other detailed features, but extend it to arbitrarily deformable models. Our approach applies zonal harmonics (ZH) which approximate spherical functions as sums of circularly symmetric Legendre polynomials around different axes. By spatially varying both the axes and coefficients of these basis functions, we can fit to spatially varying transfer signals. Compared to the spherical harmonic (SH) basis, the ZH basis yields a more compact approximation. More important, it can be trivially rotated whereas SH rotation is expensive and unsuited for dense per-vertex or per-pixel evaluation. This property allows, for the first time, PRT to be mapped onto deforming models which re-orient the local coordinate frame. We generate ZH transfer models by fitting to PRT signals simulated on meshes or simple parametric models for thin membranes and wrinkles. We show how shading with ZH transfer can be significantly accelerated by specializing to a given lighting environment. Finally, we demonstrate real-time rendering results with soft shadows, inter-reflections, and subsurface scatter on deforming models.

We compress storage and accelerate performance of precomputed radiance transfer (PRT), which captures the way an object shadows, scatters, and reflects light. PRT records over many surface points a transfer matrix. At run-time, this matrix transforms a vector of spherical harmonic coefficients representing distant, low-frequency source lighting into exiting radiance. Per-point transfer matrices form a high-dimensional surface signal that we compress using clustered principal component analysis (CPCA), which partitions many samples into fewer clusters each approximating the signal as an affine subspace. CPCA thus reduces the high-dimensional transfer signal to a low-dimensional set of per-point weights on a per-cluster set of representative matrices. Rather than computing a weighted sum of representatives and applying this result to the lighting, we apply the representatives to the lighting per-cluster (on the CPU) and weight these results per-point (on the GPU). Since the output of the matrix is lower-dimensional than the matrix itself, this reduces computation. We also increase the accuracy of encoded radiance functions with a new least-squares optimal projection of spherical harmonics onto the hemisphere. We describe an implementation on graphics hardware that performs real-time rendering of glossy objects with dynamic self-shadowing and interreflection without fixing the view or light as in previous work. Our approach also allows significantly increased lighting frequency when rendering diffuse objects and includes subsurface scattering.

Radiance transfer represents how generic source lighting is shadowed and scattered by an object to produce view-dependent appearance. We generalize by rendering transfer at two scales. A macro-scale is coarsely sampled over an object's surface, providing global effects like shadows cast from an arm onto a body. A meso-scale is finely sampled over a small patch to provide local texture. Low-order (25D) spherical harmonics represent low-frequency lighting dependence for both scales. To render, a coefficient vector representing distant source lighting is first transformed at the macro-scale by a matrix at each vertex of a coarse mesh. The resulting vectors represent a spatially-varying hemisphere of lighting incident to the meso-scale. A 4D function, called a radiance transfer texture (RTT), then specifies the surface's meso-scale response to each lighting basis component, as a function of a spatial index and a view direction. Finally, a 25D dot product of the macro-scale result vector with the vector looked up from the RTT performs the correct shading integral. We use an id map to place RTT samples from a small patch over the entire object; only two scalars are specified at high spatial resolution. Results show that bi-scale decomposition makes preprocessing practical and efficiently renders self-shadowing and interreflection effects from dynamic, low-frequency light sources at both scales.

We present a new, real-time method for rendering diffuse and glossy objects in low-frequency lighting environments that captures soft shadows, interreflections, and caustics. As a preprocess, a novel global transport simulator creates functions over the object's surface representing transfer of arbitrary, low-frequency incident lighting into transferred radiance which includes global effects like shadows and interreflections from the object onto itself. At run-time, these transfer functions are applied to actual incident lighting. Dynamic, local lighting is handled by sampling it close to the object every frame; the object can also be rigidly rotated with respect to the lighting and vice versa. Lighting and transfer functions are represented using low-order spherical harmonics. This avoids aliasing and evaluates efficiently on graphics hardware by reducing the shading integral to a dot product of 9 to 25 element vectors for diffuse receivers. Glossy objects are handled using matrices rather than vectors. We further introduce functions for radiance transfer from a dynamic lighting environment through a preprocessed object to neighboring points in space. These allow soft shadows and caustics from rigidly moving objects to be cast onto arbitrary, dynamic receivers. We demonstrate real-time global lighting effects with this approach.

Article Share on Shape by example Authors: Peter-Pike J. Sloan Microsoft Research Microsoft ResearchView Profile , Charles F. Rose Microsoft Research Microsoft ResearchView Profile , Michael F. Cohen Microsoft Research Microsoft ResearchView Profile Authors Info & Claims I3D '01: Proceedings of the 2001 symposium on Interactive 3D graphicsMarch 2001 Pages 135–143https://doi.org/10.1145/364338.364382Online:01 March 2001Publication History 205citation1,387DownloadsMetricsTotal Citations205Total Downloads1,387Last 12 Months50Last 6 weeks4 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

One of the most common tasks in computer animation is inverse-kinematics, or determining a joint configuration required to place a particular part of an articulated character at a particular location in global space. Inverse-kinematics is required at design-time to assist artists using commercial 3D animation packages, for motion capture analysis, and for run-time applications such as games. We present an efficient inverse-kinematics methodology based on the interpolation of example motions and positions. The technique is demonstrated on a number of inverse-kinematics positioning tasks for a human figure. In addition to simple positioning tasks, the method provides complete motion sequences that satisfy an inverse-kinematic goal. The interpolation at the heart of the algorithm allows an artist's influence to play a major role in ensuring that the system always generates plausible results. Due to the lightweight nature of the algorithm, we can position a character at extremely high frame rates, making the technique useful for time-critical run-time applications such as games.

A sequence of images taken along a camera trajectory captures a subset of scene appearance. If visibility space is the space that encapsulates the appearance of the scene at every conceivable pose and viewing angle, then the act of acquiring the image sequence constitutes "carving a volume in visibility space." We call such a volume a visual tunnel. The analysis of the visual tunnel allows us to do the following: predict the range of virtual camera poses in which the images can be reconstructed totally using the captured rays, predict which parts of the image can be generated for a given virtual camera pose, and plan camera paths for scene visualization at desired locations. We describe our visual tunnel concept and provide illustrative examples in 2D and 3D.

A rendering is an abstraction that favors, preserves, or even emphasizes some qualities while sacrificing, suppressing, or omitting other characteristics that are not the focus of attention.Most computer graphics rendering activities have been concerned with photorealism, i.e., trying to emulate an image that looks like a highquality photograph.This laudable goal is useful and appropriate in many applications, but not in technical illustration where elucidation of structure and technical information is the preeminent motivation.This calls for a different kind of abstraction in which technical communication is central, but art and appearance are still essential instruments toward this end.Work that has been done on computer generated technical illustrations has focused on static images, and has not included all of the techniques used to hand draw technical illustrations.A paradigm for the display of technical illustrations in a dynamic environment is presented.This display environment includes all of the benefits of computer generated technical illustrations, such as a clearer picture of shape, structure, and material composition than traditional computer graphics methods.It also includes the three-dimensional interactive strength of modem display systems.This is accomplished by using new algorithms for real time drawing of silhouette curves, algorithms which solve a number of the problems inherent in previous methods.We incorporate current non-photorealistic lighting methods, and augment them with new shadowing algorithms based on accepted techniques used by artists and studies carried out in human perception.This paper, all of the images, and a mpeg video clip are available at http

this paper, we present interactive volume visualization schemes that use ray tracing as their basic computation method

Presents a brute-force ray-tracing system for interactive volume visualization. The system runs on a conventional (distributed) shared-memory multiprocessor machine. For each pixel, we trace a ray through a volume to compute the color for that pixel. Although this method has a high intrinsic computational cost, its simplicity and scalability make it ideal for large data sets on current high-end parallel systems. To gain efficiency, several optimizations are used, including a volume bricking scheme and a shallow data hierarchy. These optimizations are used in three separate visualization algorithms: isosurfacing of rectilinear data, isosurfacing of unstructured data, and maximum-intensity projection on rectilinear data. The system runs interactively (i.e. at several frames per second) on an SGI Reality Monster. The graphics capabilities of the Reality Monster are used only for display of the final color image.

We show that it is feasible to perform interactive isosurfacing of very large rectilinear datasets with brute-force ray tracing on a conventional (distributed) shared-memory multiprocessor machine. Rather than generate geometry representing the isosurface and render with a z-buffer, for each pixel we trace a ray through a volume and do an analytic isosurface intersection computation. Although this method has a high intrinsic computational cost, its simplicity and scalability make it ideal for large datasets on current high-end systems. Incorporating simple optimizations, such as volume bricking and a shallow hierarchy, enables interactive rendering (i.e. 10 frames per second) of the 1 GByte full resolution Visible Woman dataset on an SGI Reality Monster. The graphics capabilities of the Reality Monster are used only for display of the final color image.

Traditionally, texture coordinates have been generated based solely on the model’s geometry, often even before a model’s textures have been created. With the arrival of new technologies, such as 3D paint programs, weaknesses of a static optimization pre‐process are becoming apparent. These weaknesses arise from constructing a parameterization based solely on the model’s geometry, ignoring the fact that detail is not uniformly spaced throughout the texture space. In fact, certain regions of the texture are more important than other regions. In this paper we introduce the notion of the "importance map" and describe how importance values are derived from both intrinsic properties of the texture and user‐guided highlights. Furthermore, we describe how importance maps are used to drive the texture coordinate optimization. Finally, we show how this optimization process can be integrated into a 3D painting environment, enabling periodic optimization at any stage of texture design.

It was illustrated in 1996 that the light leaving the convex hull of an object (or entering a convex region of empty space) Cm be my characterized by a 4D function over the space" of rays crowing a surface surrounding the object (or surrounding the empty apace) [10, 8].Methods to repre sent this function and quickly render individual images from this representation given an arbitrary cameras were also described.This paper extends the work outlined by Gortler et al [8] by demonstrating a taxonomy of methods to accelerate the rendering process by trading off quality for time.Given the speciiic limitation of a given hardware configuration, we discuss methods to tailor a critical time rendering strategy using these methods.