Antialiasing of Environment Maps

Various techniques have been developed that employ projections of the world as seen from a particular viewpoint. Blinn and Newell introduced reflection mapping for simulating mirror reflections on curved surfaces. Miller and Hoffman have presented a general illumination model based on environment mapping. World projections have also been used to model distant objects and to produce pictures with the fish-eye distortion required for Omnimax frames. This article proposes a uniform framework for representing and using world projections and argues that the best general-purpose representation is the is projection onto a cube. Surface shading and texture filtering are discussed in the context of environment mapping, and methods are presented for obtaining diffuse and specular surface illumination from prefiltered environment maps. Comparisons are made with ray tracing, noting that two problems with ray tracing?obtaining diffuse reflection and antialiasing specular reflection?can be handled effectively by environment mapping.

Accurate precise positioning at millimeter wave frequencies is possible due to the large available bandwidth that permits precise on-the-fly time of flight measurements using conventional air interface standards. In addition, narrow antenna beamwidths may be used to determine the angles of arrival and departure of the multipath components between the base station and mobile users. By combining accurate temporal and angular information of multipath components with a 3-D map of the environment (that may be built by each user or downloaded a-priori), robust localization is possible, even in non-line-of-sight environments. In this work, we develop an accurate 3-D ray tracer for an indoor office environment and demonstrate how the fusion of angle of departure and time of flight information in concert with a 3-D map of a typical large office environment provides a mean accuracy of 12.6 cm in line-of- sight and 16.3 cm in non-line-of-sight, over 100 receiver distances ranging from 1.5 m to 24.5 m using a single base station. We show how increasing the number of base stations improves the average non-line-of-sight position location accuracy to 5.5 cm at 21 locations with a maximum propagation distance of 24.5 m.

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.

In this paper we propose a hybrid representation of environment models by a point representation augmented to geometric representation of surface polygons reconstructed from multiple reference images, through which a real time walkthrough of a complex environment can be achieved. By the method, we start from classification of pixels of the source images into two categories, corresponding respectively to the planar and non-planar surfaces in 3D space. For the pixels corresponding to the planar surfaces, the plane coefficients are reconstructed and all their appearances in the reference images are merged to form uniformly sampled texture images by a comparison of sampling rate and resampling. For the pixels corresponding to the non-planar surfaces, a point representation is applied and the redundant pixels are removed again through sampling rate comparison. The remained pixels are organized by OBB-tree according to their space coordinates. At the same time, the holes that are unable to be captured by all the reference images are pre-filled in the preprocessing phase so that the probability of hole appearance in walkthrough is greatly reduced. Under this hybrid representation, texture mapping and point warping are employed to render the novel views, to take full advantages of the acceleration utility of graphics hardware.

This article describes a method to develop a generic approach to acquire navigation capabilities for the standard platform of the IMAV indoor competition: the Parrot AR.Drone. Our development is partly based on simulation, which requires both a realistic sensor and motion model. The AR.Drone simulation model is described and validated. Furthermore, this article describes how a visual map of the indoor environment can be made, including the effect of sensor noise. This visual map consists of a texture map and a feature map. The texture map is used for human navigation and the feature map is used by the AR.Drone to localize itself. To do so, a localization method is presented. An experiment demonstrates how well the localization works for circumstances encountered during the IMAV competition.

There are many algorithms for architectural perspective drawings. Especially, ray tracing algorithm works well for perspectives as architectural design simulations. This paper presents some techniques of applied mapping for ray tracing. These are fllowings. (1) simple fuzzy object A particle creation on the surface of a primitive is displayed on a CRT by using random number. It is available for producing tree images using personal computer. (2) texture mapping with special effective data Most useful special effect is transparent function. This function can be used many occasions for thin solid. Example, they are lettering, net, lacework and etc. What's more, if we used this mapping twice, the tree image that contents leaves shape will be available very easily. The first mapping defines leaf location on primitive and the second defines each leaf shape. (3) architectural detail modelings by 3D mapping technique We usueally get the perspective images for a simple architectural model. Meanwhile, in general practically, an architecuture consists of great many parts. We hope those whole parts should be used in the simulation modeling. Luckily many same parts of architecture keep regular positions. Using 3D mapping techniqus, such parts will be distributed regularly. Consequentially the architectural model as same as practical one can be described by fewer primiteves. And we can get more realistic images of architecture easily.

The thesis investigates a way to perform realistic three-dimensional texturing of ray-traced objects that is especially useful for objects with irregular surfaces. Two similar existing methods are texture mapping and particle systems. The thesis describes these methods and points out their strengths and weaknesses. It then proposes an alternative to these methods that uses a construct called a lattice. Lattices make as fast ray tracers, but they are inexact. As long as lattices are used for small objects, though, their inexactness doesn't show on the scale of the display, and the result is acceptable. The thesis also shows how lattices fit with the more traditional largescale ray tracer, combining lattices with a Constructive Solid Geometry (CSG) object model to pr?duce several examples. . Time and memory space considerations are major constraints on lattices. The thesis discusses these limitations and how they can be reduced.

Visual coherence between real and virtual objects is important in mixed reality (MR), and illumination consistency is one of the key aspects to achieve coherence. Apart from matching the illumination of the virtual objects with the real environments, the change of illumination on the real scenes produced by the inserted virtual objects should also be considered but is difficult to compute in real-time due to the heavy computation demands of global illumination. In this work, we propose delta path tracing (DPT), which only computes the radiance blocked by the virtual objects from the light sources at the primary hit points of Monte Carlo path tracing, then combines the blocked radiance and multi-bounce indirect illumination with the image of the real scene. Multiple importance sampling (MIS) between BRDF and environment map is performed to handle all-frequency environment maps captured by a panorama camera. Compared to conventional differential rendering methods, our method can remarkably reduce the number of times required to access the environment map and avoid rendering scenes twice. Therefore, the performance can be significantly improved. We implement our method using hardware-accelerated ray tracing on modern GPUs, and the results demonstrate that our method can render global illumination at real-time frame rates and produce plausible visual coherence between real and virtual objects in MR environments.

Abstract. Waveform LiDAR systems is widely used in several fields such as terrain survey, disaster monitoring and forest monitoring. Especially, in forest research, using an echo signal is expected for understanding structural characteristics of the forest. However, an echo signal highly depends on the sensor configuration, the footprint size, the canopy structure, and terrain condition. Therefore, it is not easy to understand the forest attributes from the echo signal. In this paper, we describe the development and application of model which to simulate laser intersections within ideal forest environments and to visualize intersections. The developed model has three components. The first component was a creation of the forest environment as full polygon in 3DCG software. Characteristics of the forest was decided by individual trees which were generated by the plant growth model using species and planting years as the initial parameter. The second component was a simulation using a ray tracing to calculate intersections between the forest object and the modelled laser beam. In this study, a laser beam with a specific footprint and a pulse width was defined by spatiotemporal features. In point of view of spatial feature, numerous sub laser beams were generated within a specific footprint to make the laser beam hit the target uniformly. Each sub laser beam had the intensity which was calculated by both the distance from the center of laser beam and the TEM00. On the other hand, in point of view of time feature, each sub laser beam was defined as several particles based on the sampling rate. Each particle had the intensity which was calculated by the pulse width and the sampling rate. The third component was a creation of an echo signal of a specific footprint using the calculated intersections and its intensity, reflectance of target at intersections and sampling rate. Moreover, the developed model had a view function that was able to show the calculated intersections on the surface of target object. As results of simulation of ideal forest environment scenarios, the developed model demonstrated that the model generated the echo signal of different environments well and the viewer function helped to understand the interactions between sub laser beams and target objects.

This paper presents a technique for representing and displaying high dynamic-range texture maps (HDRTMs) using current graphics hardware. Dynamic range in real-world environments often far exceeds the range representable in 8-bit per-channel texture maps. The increased realism afforded by a highdynamic range representation provides improved fidelity and expressiveness for interactive visualization of image-based models. Our technique allows for realtime rendering of scenes with arbitrary dynamic range, limited only by available texture memory. In our technique, high-dynamic range textures are decomposed into sets of 8- bit textures. These 8-bit textures are dynamically reassembled by the graphics hardware's programmable multitexturing system or using multipass techniques and framebuffer image processing. These operations allow the exposure level of the texture to be adjusted continuously and arbitrarily at the time of rendering, correctly accounting for the gamma curve and dynamic range restrictions of the display device. Further, for any given exposure only two 8-bit textures must be resident in texture memory simultaneously. We present implementation details of this technique on various 3D graphics hardware architectures. We demonstrate several applications, including high-dynamic range panoramic viewing with simulated auto-exposure, real-time radiance environment mapping, and simulated Fresnel reflection.

Efficient and realistic rendering of cloth is of great interest especially in the context of e-commerce. Aside from the simulation of cloth draping, the rendering has to provide the look and feel of the fabric itself. In this paper we present a novel interactive rendering algorithm to preserve this look and feel of different fabrics. This is done by using the bidirectional texture function (BTF) of the fabric, which is acquired from a rectangular probe and after synthesis, mapped onto the simulated geometry. Instead of fitting a special type of bidirectional reflection distribution function (BRDF) model to each texel of our BTF, we generate view-dependent texture-maps using a principal component analysis of the original data. These view-dependent texture maps are then illuminated and rendered using either point-light sources or high dynamic range environment maps by exploiting current graphics hardware. In both cases, self-shadowing caused by geometry is taken into account. For point light sources, we also present a novel method to generate smooth shadow boundaries on the geometry. Depending on the geometrical complexity and the sampling density of the environment map, the illumination can be changed interactively. To ensure interactive frame rates for denser samplings or more complex objects, we introduce a principal component based decomposition of the illumination of the geometry. The high quality of the results is demonstrated by several examples. The algorithm is also suitable for materials other than cloth, as far as these materials have a similar reflectance behavior.

In photorealistic rendering, refraction is a vital optical phenomenon for transparent objects. This study proposes a real-time image-space method for approximate multiple refraction. First, a depth-peeling technique is used to disassemble a 3D polygonal model into four layers of normal and depth textures. Next, a modified ray-height-field intersection algorithm is employed to resolve discontinuities between the layers and compute the intersection, refraction, and total internal reflection. Finally, an environment map with a refraction vector is used to compute the final shading. The image space and shader technique enables generating a maximum of four bounces to increase the refraction detail and handle more complex scenes compared with those examined in previous methods. We performed several experiments with various scenes and the results showed the feasibility and quality of the proposed multi-refraction method. In addition, the rendering efficiency was demonstrated by comparing the proposed method with GPU-based ray tracing.

Radio environment map (REM) play an important role in managing frequency resources. In this paper, we exploit the sparsity of the signal source in spatial domain to construct a three-dimensional radio environment map(3D-REM) by compressed sensing (CS). Firstly, we proposed a spatial sampling points selection algorithm based on minimizing the column correlation values of sensing matrix. It is proved that the proposed algorithm can improve the recovery accuracy of REM under the same sampling rate. In practical scenarios, there may be some limitations to place sampling receivers in some specific locations, e.g., obstacles. Therefore, we consider a limted set of points which can not be sampled. Simulated annealing (SA) algorithm is used to find candidates when they are not available. Simulation results show that the proposed scheme can achieve better performance of recovery accuracy of REM than other algorithms.

This paper describes the development of a binocular eye tracking Virtual Reality system for aircraft inspection training. The aesthetic appearance of the environment is driven by standard graphical techniques augmented by realistic texture maps of the physical environment. A "virtual flashlight" is provided to simulate a tool used by inspectors. The user's gaze direction, as well as head position and orientation, are tracked to allow recording of the user's gaze locations within the environment. These gaze locations, or scanpaths, are calculated as gaze/polygon intersections, enabling comparison of fixated points with stored locations of artificially generated defects located in the environment interior. Recorded scanpaths provide a means of comparison of the performance of experts to novices, thereby gauging the effects of training.

For convincing realistic scenes objects with free‐form surfaces are essential. Especially for photorealistic rendering pure polygonal models are often not sufficient. We present a new kind of algorithm to render free‐form surfaces in a rendering system based on ray tracing. We describe a triangular patch as usual by its three points and normal vectors, but base the intersection calculation as well on the viewpoint of the camera (or, in general, on the ray itself). Hence, the shape of the object depends to some extent on the sampling rays. However, the resulting differences of, for instance, the shape of the silhouette to the shape of the corresponding shadow is usually not perceived by the observer of the rendered image. Because we perform a direct computation without a tessellation process, the resulting surface, its shadows, and its reflections appear smooth independent of the distance to the camera. Furthermore, the memory consumption depends only linearly on the number of input triangles. Special features like creases, T‐vertices, and darts are also well supported. The computed uv‐coordinates provide a direct means for texture mapping whose visual appearance improves significantly compared to triangle meshes of the same resolution.