We describe Embree, an open source ray tracing framework for x86 CPUs. Embree is explicitly designed to achieve high performance in professional rendering environments in which complex geometry and incoherent ray distributions are common. Embree consists of a set of low-level kernels that maximize utilization of modern CPU architectures, and an API which enables these kernels to be used in existing renderers with minimal programmer effort. In this paper, we describe the design goals and software architecture of Embree, and show that for secondary rays in particular, the performance of Embree is competitive with (and often higher than) existing state-of-the-art methods on CPUs and GPUs.

High-quality head mounted displays are becoming available in the consumer space. These displays provide an immersive gaming experience by filling the wearer's field of view. To achieve immersion with low cost, a commodity display panel is placed a short distance in front of each eye, and wide-angle optics are used to bring the image into focus. However, these optics introduce spatial and chromatic distortion into the image seen by the viewer. As a result, the images to be displayed must be pre-warped to cancel this distortion. This correction can be performed by warping the image in a post-processing step, by warping the scene geometry before rendering, or by modeling corrective optics in the virtual camera.

A key problem in applications such as soft shadows and defocus blur is to identify points or primitives which are inside a volume of space. For example, the soft shadow computation involves finding surfaces which pass in front of an area light as viewed from a point p in the scene. The desired surfaces are those which are inside a frustum defined by the light and p , and can be found by intersecting the frustum with an acceleration structure over geometry. However, accurately computing this intersection is computationally intensive. In this article, we introduce a homogeneous transform which reduces the computation required to determine the set of points or primitives which are inside a tetrahedral volume. The transform converts tetrahedra into axis-aligned boxes, substantially reducing the cost of intersection with an axis-aligned acceleration structure over points or primitives. We describe the application of this transform to soft shadows and defocus blur, and briefly consider potential uses of the underlying mathematical approach in higher-dimensional problems.

Scientific visualization is the process of transforming raw numeric data into a visual form, and is a key element of computational science. While many tools exist, they are unnecessarily difficult to use. This complexity increases time to insight and inhibits casual inquiry. The complexity derives from the need to support arbitrarily formatted data and many visualization algorithms. EnVision addresses both sources of complexity. Its design is predicated on two key insights. First, though the number of data file formats is unbounded, the structure of any one can be described using a small number of parameters. Second, the set of visualization algorithms applicable to a given type of data is small, and the subset used within a specific scientific discipline is smaller. EnVision utilizes domain-specific knowledge and user-directed semi-automation to dramatically simplify data importation and visualization algorithm selection. Its Web-based interface facilitates access to remote hardware resources and provides a collaborative visualization environment.

We introduce a straightforward, robust, and efficient algorithm for rendering high-quality soft shadows in dynamic scenes. Each frame, points in the scene visible from the eye are inserted into a spatial acceleration structure. Shadow umbrae are computed by sampling the scene from the light at the image plane coordinates given by the stored points. Penumbrae are computed at the same set of points, per silhouette edge, in two steps. First, the set of points affected by a given edge is estimated from the expected light-view screen-space bounds of the corresponding penumbra. Second, the actual overlap between these points and the penumbra is computed analytically directly from the occluding geometry. The umbral and penumbral sources of occlusion are then combined to determine the degree of shadow at the eye-view pixel corresponding to each sample point. An implementation of this algorithm for the Larrabee architecture yields from 27 to 33 frames per second in simulation for scenes from a modern game, and produces significantly higher image quality than other recent methods in the real-time domain.

The classical Z-buffer visibility algorithm samples a scene at regularly spaced points on an image plane. Previously, we introduced an extension of this algorithm called theirregular Z-bufferthat permits sampling of the scene from arbitrary points on the image plane. These sample points are stored in a two-dimensional spatial data structure. Here we present a set of architectural enhancements to the classical Z-buffer acceleration hardware which supports efficient execution of the irregular Z-buffer. These enhancements enable efficient parallel construction and query of certain irregular data structures, including the grid of linked lists used by our algorithm. The enhancements include flexible atomic read-modify-write units located near the memory controller, an internal routing network between these units and the fragment processors, and a MIMD fragment processor design. We simulate the performance of this new architecture and demonstrate that it can be used to render high-quality shadows in geometrically complex scenes at interactive frame rates. We also discuss other uses of the irregular Z-buffer algorithm and the implications of our architectural changes in the design of chip-multiprocessors.