We present novel parallel algorithms for collision detection and separation distance computation for rigid and deformable models that exploit the computational capabilities of many-core GPUs. Our approach uses thread and data parallelism to perform fast hierarchy construction, updating, and traversal using tight- fitting bounding volumes such as oriented bounding boxes (OBB) and rectangular swept spheres (RSS). We also describe efficient algorithms to compute a linear bounding volume hierarchy (LBVH) and update them using refitting methods. Moreover, we show that tight-fitting bounding volume hierarchies offer improved performance on GPU-like throughput architectures. We use our algorithms to perform discrete and continuous collision detection including self-collisions, as well as separation distance computation between non-overlapping models. In practice, our approach (gProximity) can perform these queries in a few milliseconds on a PC with NVIDIA GTX 285 card on models composed of tens or hundreds of thousands of triangles used in cloth simulation

We present a novel method for tuning geometric acoustic simulations based on ray tracing. Our formulation computes sound propagation paths from source to receiver and exploits the independence of visibility tests and validation tests to dynamically guide the simulation to high accuracy and performance. Our method makes no assumptions of scene layout and can account for moving sources, receivers, and geometry. We combine our guidance algorithm with a fast GPU sound propagation system for interactive simulation. Our implementation efficiently computes early specular paths and first order diffraction with a multiview tracing algorithm. We couple our propagation simulation with an audio output system supporting a high order interpolation scheme that accounts for attenuation, cross fading, and delay. The resulting system can render acoustic spaces composed of thousands of triangles interactively.

We present a novel scheme for automatically generating line drawings from 2D images, aiming to facilitate effective visual communication. In contrast to conventional edge detectors, our technique imitates the human line drawing process and consists of two parts: line extraction and line rendering. We propose a novel line extraction method based on likelihood-function estimation, which effectively finds the genuine shape boundaries. We consider the feature scale and the blurriness of lines with which the detail and the focus-level of lines are controlled in the rendering. We also employ stroke textures to provide a variety of illustration styles. Experimental results demonstrate that our technique generates various kinds of line drawings from 2D images enabled by the control over detail, focus, and style.

The physical world consists of spatially varying media, such as the atmosphere and the ocean, in which light and sound propagates along non-linear trajectories. This presents a challenge to existing ray-tracing based methods, which are widely adopted to simulate propagation due to their efficiency and flexibility, but assume linear rays. We present a novel algorithm that traces analytic ray curves computed from local media gradients, and utilizes the closed-form solutions of both the intersections of the ray curves with planar surfaces, and the travel distance. By constructing an adaptive unstructured mesh, our algorithm is able to model general media profiles that vary in three dimensions with complex boundaries consisting of terrains and other scene objects such as buildings. Our analytic ray curve tracer with the adaptive mesh improves the efficiency considerably over prior methods. We highlight the algorithm's application on simulation of visual and sound propagation in outdoor scenes.

Outdoor sound propagation, which propagates sound through inhomogeneous, moving media with complex obstacles, presents challenging scenarios for computational simulation. In this paper, we present a ray-tracing method that uses analytic ray curves as tracing primitives in order to improve the efficiency of outdoor sound propagation in fully general settings. This ray-curve tracer inherits the efficiency and flexibility of rectilinear ray tracers in handling boundary surfaces, and it overcomes the performance limitations imposed by approximating the curved propagation paths in inhomogeneous media with rectilinear rays. Adaptive media traversal, as well as acceleration structures for surfaces intersections, lead to further savings in computation. Our method's speedup over existing ray models, at least an order of magnitude for simple 2D scenarios and up to two orders of magnitude for 3D complex scenes, is demonstrated on outdoor benchmark scenes.