Many lighting methods used in computer graphics such as indirect illumination can have very high computational costs and need to be approximated for real-time applications. These costs can be reduced by means of upsampling techniques which tend to introduce artifacts and affect the visual quality of the rendered image. This paper suggests a versatile approach for accelerating the rendering of screen space methods while maintaining the visual quality. This is achieved by exploiting the low frequency nature of many of these illumination methods and the geometrical continuity of the scene. First the screen space is dynamically divided into separate sub-images, then the illumination is rendered for each sub-image in an adequate resolution and finally the sub-images are put together in order to compose the final image. Therefore we identify edges in the scene and generate masks precisely specifying which part of the image is included in which sub-image. The masks therefore determine which part of the image is rendered in which resolution. A step wise upsampling and merging process then allows optically soft transitions between the different resolution levels. For this paper, the introduced multi-resolution rendering method was implemented and tested on three commonly used lighting methods. These are screen space ambient occlusion, soft shadow mapping and screen space global illumination.
Nichols and Wyman @cite_20 describe a real-time technique for rendering indirect illumination using multi-resolution splatting. They use min-max mipmaps to find the discontinuities in the geometry. Using these discontinuities, the image space is hierarchically divided into smaller squares, so that areas with higher-frequency components obtain a finer resolution. After the image is completely split into such splats' of an appropriate size, the indirect illumination is rendered in all resolutions and the layers are then combined by upsampling to produce the final image. Our technique differs from the algorithm presented by Nichols and Wyman among other things in the method used to decide which resolution to render in. We can apply more flexible filters depending on the situation, while their approach using min-max mipmaps can only find geometric discontinuities. We also use a different approach to combine the final images that prevents visible artifacts. Finally, our technique is not only specialized for indirect illumination using Reflective Shadow Maps, but can also be applied and optimized for various lighting effects due to its high flexibility.
@cite_20
2020853194 2113507517 124515947 2076669957
Global illumination provides a visual richness not achievable with the direct illumination models used by most interactive applications. To generate global effects, numerous approximations attempt to reduce global illumination costs to levels feasible in interactive contexts. One such approximation, reflective shadow maps, samples a shadow map to identify secondary light sources whose contributions are splatted into eye space. This splatting introduces significant overdraw that is usually reduced by artificially shrinking each splat's radius of influence. This paper introduces a new multiresolution approach for interactively splatting indirect illumination. Instead of reducing GPU fill rate by reducing splat size, we reduce fill rate by rendering splats into a multiresolution buffer. This takes advantage of the low-frequency nature of diffuse and glossy indirect lighting, allowing rendering of indirect contributions at low resolution where lighting changes slowly and at high-resolution near discontinuities. Because this multiresolution rendering occurs on a per-splat basis, we can significantly reduce fill rate without arbitrarily clipping splat contributions below a given threshold-those regions simply are rendered at a coarse resolution. We present an approach to add true fine-scale spatio-temporal shape detail to dynamic scene geometry captured from multi-view video footage. Our approach exploits shading information to recover the millimeter-scale surface structure, but in contrast to related approaches succeeds under general unconstrained lighting conditions. Our method starts off from a set of multi-view video frames and an initial series of reconstructed coarse 3D meshes that lack any surface detail. In a spatio-temporal maximum a posteriori probability (MAP) inference framework, our approach first estimates the incident illumination and the spatially-varying albedo map on the mesh surface for every time instant. Thereafter, albedo and illumination are used to estimate the true geometric detail visible in the images and add it to the coarse reconstructions. The MAP framework uses weak temporal priors on lighting, albedo and geometry which improve reconstruction quality yet allow for temporal variations in the data. Single-shot structured light methods allow 3D reconstruction of dynamic scenes. However, such methods lose spatial resolution and perform poorly around depth discontinuities. Previous single-shot methods project the same pattern repeatedly; thereby spatial resolution is reduced even if the scene is static or has slowly moving parts. We present a structured light system using a sequence of shifted stripe patterns that is decodable both spatially and temporally. By default, our method allows single-shot 3D reconstruction with any of our projected patterns by using spatial windows. Moreover, the sequence is designed so as to progressively improve the reconstruction quality around depth discontinuities by using temporal windows. Our method enables motion-aware reconstruction for each pixel: The best spatio-temporal window is automatically selected depending on the scene structure, motion, and the number of available images. This significantly reduces the number of pixels around discontinuities where depth cannot be recovered in traditional approaches. Our decoding scheme extends the adaptive window matching commonly used in stereo by incorporating temporal windows with 1D spatial windows. We demonstrate the advantages of our approach for a variety of scenarios including thin structures, dynamic scenes, and scenes containing both static and dynamic regions. This paper focuses on efficient rendering based on pre-computed light transport, with realistic materials and shadows under all-frequency direct lighting such an environment maps. The basic difficulty is representation and computation in the 6D space of light direction, view direction, and surface position. While image-based and synthetic methods for real-time rendering have been proposed, they do not scale to high sampling rates with variation of both lighting and viewpoint. Current approaches are therefore limited to lower dimensionality (only lighting or viewpoint variation, not both) or lower sampling rates (low frequency lighting and materials). We propose a new mathematical and computational analysis of pre-computed light transport. We use factored forms, separately pre-computing and representing visibility and material properties. Rendering then requires computing triple product integrals at each vertex, involving the lighting, visibility and BRDF. Our main contribution is a general analysis of these triple product integrals, which are likely to have broad applicability in computer graphics and numerical analysis. We first determine the computational complexity in a number of bases like point samples, spherical harmonics and wavelets. We then give efficient linear and sublinear-time algorithms for Haar wavelets, incorporating non-linear wavelet approximation of lighting and BRDFs. Practically, we demonstrate rendering of images under new lighting and viewing conditions in a few seconds, significantly faster than previous techniques.