2168693
Thrifty Final Gather for Radiosity
Finite Element methods are well suited to the computation of the light distribution in mostly diffuse scenes, but the resulting mesh is often far from optimal to accurately represent illumination. Shadow boundaries are hard to capture in the mesh, and the illumination may contain artifacts due to light transports at different mesh hierarchy levels. To render a high quality image a costly final gather reconstruction step is usually done, which re-evaluates the illumination integral for each pixel. In this paper an algorithm is presented which significantly speeds up the final gather by exploiting spatial and directional coherence information taken from the radiosity solution. Senders are classified, so that their contribution to a pixel is either interpolated from the radiosity solution or recomputed with an appropriate number of new samples. By interpolating this sampling pattern over the radiosity mesh, continuous solutions are obtained.
13902074
Enhancements to Directional Coherence Maps
Directional Coherence Maps as proposed by Guo in '98 are a very efficient acceleration technique for ray tracing based global illumination renderers. It vastly reduces the number of pixels which have to be computed exactly by identifying regions which are suitable for interpolation. By using oriented finite elements for interpolation, the sampling density can be kept low for large regions of the target image. In this paper we describe extensions of the method. An improved object test is presented which prevents that small objects are missed. Additionally, it is shown how to handle textures efficiently, which was not possible with the original approach.
2803614
Exchanging Faces in Images
Pasting somebody’s face into an existing image with traditional photo retouching and digital image processing tools has only been possible if both images show the face from the same viewpoint and with the same illumination. However, this is rarely the case for given pairs of images. We present a system that exchanges faces across large differences in viewpoint and illumination. It is based on an algorithm that estimates 3D shape and texture along with all relevant scene parameters, such as pose and lighting, from single images. Manual interaction is reduced to clicking on a set of about 7 feature points, and marking the hairline in the target image. The system can be used for image processing, virtual try-on of hairstyles, and face recognition. By separating face identity from imaging conditions, our approach provides an abstract representation of images and a novel, high-level tool for image manipulation.
1246635
Backward compatible high dynamic range MPEG video compression
To embrace the imminent transition from traditional low-contrast video (LDR) content to superior high dynamic range (HDR) content, we propose a novel backward compatible HDR video compression (HDR MPEG) method. We introduce a compact reconstruction function that is used to decompose an HDR video stream into a residual stream and a standard LDR stream, which can be played on existing MPEG decoders, such as DVD players. The reconstruction function is finely tuned to the content of each HDR frame to achieve strong decorrelation between the LDR and residual streams, which minimizes the amount of redundant information. The size of the residual stream is further reduced by removing invisible details prior to compression using our HDR-enabled filter, which models luminance adaptation, contrast sensitivity, and visual masking based on the HDR content. Designed especially for DVD movie distribution, our HDR MPEG compression method features low storage requirements for HDR content resulting in a 30% size increase to an LDR video sequence. The proposed compression method does not impose restrictions or modify the appearance of the LDR or HDR video. This is important for backward compatibility of the LDR stream with current DVD appearance, and also enables independent fine tuning, tone mapping, and color grading of both streams.
190423
Multi-level partition of unity implicits
We present a new shape representation, the multi-level partition of unity implicit surface, that allows us to construct surface models from very large sets of points. There are three key ingredients to our approach: 1) piecewise quadratic functions that capture the local shape of the surface, 2) weighting functions (the partitions of unity) that blend together these local shape functions, and 3) an octree subdivision method that adapts to variations in the complexity of the local shape.Our approach gives us considerable flexibility in the choice of local shape functions, and in particular we can accurately represent sharp features such as edges and corners by selecting appropriate shape functions. An error-controlled subdivision leads to an adaptive approximation whose time and memory consumption depends on the required accuracy. Due to the separation of local approximation and local blending, the representation is not global and can be created and evaluated rapidly. Because our surfaces are described using implicit functions, operations such as shape blending, offsets, deformations and CSG are simple to perform.