Realistic computer generated images are computed by combining geometric effects, reflectance models for several captured and phenomenological materials, and real-world lighting according to mathematical models of physical light transport. Several important lighting phenomena should be considered when targeting realistic image simulation. A combination of soft and hard shadows, which arise from the interaction of surface and light geometries, provide necessary shape perception cues for a viewer. A wide variety of realistic materials, from physically-captured reflectance datasets to empirically designed mathematical models, modulate the virtual surface appearances in a manner that can further dissuade a viewer from considering the possibility of computational image synthesis over that of reality. Lastly, in many important cases, light reflects off many different surfaces before entering the eye. These secondary effects can be critical in grounding the viewer in a virtual world, since the human visual system is adapted to the physical world, where such effects are constantly in play. Simulating each of these effects is challenging due to their individual underlying complexity. The net complexity is compounded when several effects are combined. This thesis will investigate real-time approaches for simulating these effects under stringent performance and memory constraints, and with varying degrees of interactivity. In order to make these computations tractable given these added constraints, I will use data and signal analysis techniques to identify predictable patterns in the different spatial and angular signals used during image synthesis. The results of this analysis will be exploited with several analytic and data-driven mathematical models that are both efficient, and yield accurate approximations with predictable and controllable error.

Realistic computer generated images are computed by combining geometric effects, reflectance models for several captured and phenomenological materials, and real-world lighting according to mathematical models of physical light transport. Several important lighting phenomena should be considered when targeting realistic image simulation. A combination of soft and hard shadows, which arise from the interaction of surface and light geometries, provide necessary shape perception cues for a viewer. A wide variety of realistic materials, from physically-captured reflectance datasets to empirically designed mathematical models, modulate the virtual surface appearances in a manner that can further dissuade a viewer from considering the possibility of computational image synthesis over that of reality. Lastly, in many important cases, light reflects off many different surfaces before entering the eye. These secondary effects can be critical in grounding the viewer in a virtual world, since the human visual system is adapted to the physical world, where such effects are constantly in play. Simulating each of these effects is challenging due to their individual underlying complexity. The net complexity is compounded when several effects are combined. This thesis will investigate real-time approaches for simulating these effects under stringent performance and memory constraints, and with varying degrees of interactivity. In order to make these computations tractable given these added constraints, I will use data and signal analysis techniques to identify predictable patterns in the different spatial and angular signals used during image synthesis. The results of this analysis will be exploited with several analytic and data-driven mathematical models that are both efficient, and yield accurate approximations with predictable and controllable error.

Global illumination techniques are used to improve the realism of 3D scenes. Calculating accurate global illumination requires a method for solving the rendering equation. However, the integral form of this equation cannot be evaluated. This thesis presents research in non real-time illumination techniques which are evaluated with a finite number of light rays. This includes a new technique which improves realism of the scene over traditional techniques. All computer rendering requires distortion free texture mapping to appear plausible to the eye. Inverse texture mapping, however, can be numerically unstable and computationally expensive. Alternative techniques for texture mapping and texture coordinate generation were developed to simplify rendering. Real-time rendering is improved by pre-calculating non real-time reflections. The results of this research demonstrate that a polynomial approximation of reflected light can be more accurate than a constant approximation. The solution improves realism and makes use of new features in graphics hardware. / May 2007

Global illumination techniques are used to improve the realism of 3D scenes. Calculating accurate global illumination requires a method for solving the rendering equation. However, the integral form of this equation cannot be evaluated. This thesis presents research in non real-time illumination techniques which are evaluated with a finite number of light rays. This includes a new technique which improves realism of the scene over traditional techniques. All computer rendering requires distortion free texture mapping to appear plausible to the eye. Inverse texture mapping, however, can be numerically unstable and computationally expensive. Alternative techniques for texture mapping and texture coordinate generation were developed to simplify rendering. Real-time rendering is improved by pre-calculating non real-time reflections. The results of this research demonstrate that a polynomial approximation of reflected light can be more accurate than a constant approximation. The solution improves realism and makes use of new features in graphics hardware.

Global illumination techniques are used to improve the realism of 3D scenes. Calculating accurate global illumination requires a method for solving the rendering equation. However, the integral form of this equation cannot be evaluated. This thesis presents research in non real-time illumination techniques which are evaluated with a finite number of light rays. This includes a new technique which improves realism of the scene over traditional techniques. All computer rendering requires distortion free texture mapping to appear plausible to the eye. Inverse texture mapping, however, can be numerically unstable and computationally expensive. Alternative techniques for texture mapping and texture coordinate generation were developed to simplify rendering. Real-time rendering is improved by pre-calculating non real-time reflections. The results of this research demonstrate that a polynomial approximation of reflected light can be more accurate than a constant approximation. The solution improves realism and makes use of new features in graphics hardware.

In this thesis, we explore detailed voxel scene compression methods and editing thereof with the goal to design an interactive voxel viewer/editor, for e.g. a 3D printing appli- cation. We present state-of-the-art GPU compatible data structures and compare them. On top of the chosen data structure, we build standard editing tools known from 2D, capable of changing voxel color in real-time even on lower end machines. 1

Algorithms are presented that enable the use of vector graphics representations of images in texture maps for 3D real time rendering. Vector graphics images are resolution independent and can be zoomed arbitrarily without losing detail or crispness. Many important types of images, including text and other symbolic information, are best represented in vector form. Vector graphics textures can also be used as transparency mattes to augment geometric detail in models via trim curves. Spline curves are used to represent boundaries around regions in standard vector graphics representations, such as PDF and SVG. Antialiased rendering of such content can be obtained by thresholding implicit representations of these curves. The distance function is an especially useful implicit representation. Accurate distance function computations would also allow the implementation of special effects such as embossing. Unfortunately, computing the true distance to higher order spline curves is too expensive for real time rendering. Therefore, normally either the distance is approximated by normalizing some other implicit representation or the spline curves are approximated with simpler primitives. In this thesis, three methods for rendering vector graphics textures in real time are introduced, based on various approximations of the distance computation. The first and simplest approach to the distance computation approximates curves with line segments. Unfortunately, approximation with line segments gives only C0 continuity. In order to improve smoothness, spline curves can also be approximated with circular arcs. This approximation has C1 continuity and computing the distance to a circular arc is only slightly more expensive than computing the distance to a line segment. Finally an iterative algorithm is discussed that has good performance in practice and can compute the distance to any parametrically differentiable curve (including polynomial splines of any order) robustly. This algorithm is demonstrated in the context of a system capable of real-time rendering of SVG content in a texture map on a GPU. Data structures and acceleration algorithms in the context of massively parallel GPU architectures are also discussed. These data structures and acceleration structures allow arbitrary vector content (with space-variant complexity, and overlapping regions) to be represented in a random-access texture.

Algorithms are presented that enable the use of vector graphics representations of images in texture maps for 3D real time rendering. Vector graphics images are resolution independent and can be zoomed arbitrarily without losing detail or crispness. Many important types of images, including text and other symbolic information, are best represented in vector form. Vector graphics textures can also be used as transparency mattes to augment geometric detail in models via trim curves. Spline curves are used to represent boundaries around regions in standard vector graphics representations, such as PDF and SVG. Antialiased rendering of such content can be obtained by thresholding implicit representations of these curves. The distance function is an especially useful implicit representation. Accurate distance function computations would also allow the implementation of special effects such as embossing. Unfortunately, computing the true distance to higher order spline curves is too expensive for real time rendering. Therefore, normally either the distance is approximated by normalizing some other implicit representation or the spline curves are approximated with simpler primitives. In this thesis, three methods for rendering vector graphics textures in real time are introduced, based on various approximations of the distance computation. The first and simplest approach to the distance computation approximates curves with line segments. Unfortunately, approximation with line segments gives only C0 continuity. In order to improve smoothness, spline curves can also be approximated with circular arcs. This approximation has C1 continuity and computing the distance to a circular arc is only slightly more expensive than computing the distance to a line segment. Finally an iterative algorithm is discussed that has good performance in practice and can compute the distance to any parametrically differentiable curve (including polynomial splines of any order) robustly. This algorithm is demonstrated in the context of a system capable of real-time rendering of SVG content in a texture map on a GPU. Data structures and acceleration algorithms in the context of massively parallel GPU architectures are also discussed. These data structures and acceleration structures allow arbitrary vector content (with space-variant complexity, and overlapping regions) to be represented in a random-access texture.

<p>This dissertation presents a method capable of smoothing the silhouette of a 3D model using interpolation to find smooth edges. The method has as goal to be used with normal mapping to improve the performance and give a better result with a low polygonal count. To do this the lines located on the silhouette of a model is interpolated to find a curve that is used as clipping frame in the stencil buffer. This method is able to modify the silhouette for the better. The amount of interpolation is rather limited.</p>

This dissertation presents a method capable of smoothing the silhouette of a 3D model using interpolation to find smooth edges. The method has as goal to be used with normal mapping to improve the performance and give a better result with a low polygonal count. To do this the lines located on the silhouette of a model is interpolated to find a curve that is used as clipping frame in the stencil buffer. This method is able to modify the silhouette for the better. The amount of interpolation is rather limited.