Results 1  10
of
53
Casting Curved Shadows on Curved Surfaces
 In Computer Graphics (SIGGRAPH ’78 Proceedings
, 1978
"... Shadowing has historically been used to increase the intelligibility of scenes in electron microscopy and aerial survey. Various methods have been published for the determination of shadows in computer synthesized scenes. The display of shadows may make the shape and relative position of objects i ..."
Abstract

Cited by 401 (1 self)
 Add to MetaCart
Shadowing has historically been used to increase the intelligibility of scenes in electron microscopy and aerial survey. Various methods have been published for the determination of shadows in computer synthesized scenes. The display of shadows may make the shape and relative position of objects in such scenes more comprehensible; it is a technique lending vividness and realism to computer animation. To date, algorithms for the determination of shadows have been restricted to scenes constructed of planar polygons. A simple algorithm is described which utilizes Zbuffer visible surface computation to display shadows cast by objects modelled of smooth surface patches. The method can be applied
Painterly Rendering for Animation
 In SIGGRAPH 96 Conference Proceedings
, 1996
"... We present a technique for rendering animations in a painterly style. The difficulty in using existing still frame methods for animation is getting the paint to “stick ” to surfaces rather than randomly change with each frame, while still retaining a handcrafted look. We extend the still frame meth ..."
Abstract

Cited by 227 (2 self)
 Add to MetaCart
(Show Context)
We present a technique for rendering animations in a painterly style. The difficulty in using existing still frame methods for animation is getting the paint to “stick ” to surfaces rather than randomly change with each frame, while still retaining a handcrafted look. We extend the still frame method to animation by solving two major specific problems of previous techniques. First our method eliminates the “shower door ” effect in which an animation appears as if it were being viewed through textured glass because brush strokes stick to the viewplane not to the animating surfaces. Second, our technique provides for frametoframe coherence in animations so that the resulting frames do not randomly change every frame. To maintain coherence, we model surfaces as 3d particle sets which are rendered as 2d paint brush strokes in screen space much like an artist lays down brush strokes on a canvas. We use geometric and lighting properties of the surfaces to control the appearanceof brush strokes. This powerful combination of using 3d particles, surface lighting information, and rendering 2d brush strokes in screen space gives us the painterly style we desire and forces the brush strokes to stick to animating surfaces. By varying lighting and choosing brush stroke parameters we can create many varied painterly styles. We illustrate the method with images and animated sequences and present specific technical and creative suggestions for achieving different looks.
A survey of visibility for walkthrough applications
 IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER
, 2003
"... Visibility algorithms for walkthrough and related applications have grown into a significant area, spurred by the growth in the complexity of models and the need for highly interactive ways of navigating them. In this survey, we review the fundamental issues in visibility and conduct an overview of ..."
Abstract

Cited by 185 (9 self)
 Add to MetaCart
Visibility algorithms for walkthrough and related applications have grown into a significant area, spurred by the growth in the complexity of models and the need for highly interactive ways of navigating them. In this survey, we review the fundamental issues in visibility and conduct an overview of the visibility culling techniques developed in the last decade. The taxonomy we use distinguishes between pointbased and fromregion methods. Pointbased methods are further subdivided into object and imageprecision techniques, while fromregion approaches can take advantage of the cellandportal structure of architectural environments or handle generic scenes.
Hidden Surface Removal Using Polygon Area Sorting
 Computer Graphics
, 1977
"... A polygon hidden surface and hidden line removal algorithm is presented. The algorithm recursively subdivides the image into polygon shaped windows until the depth order within the window is found. Accuracy of the input data is preserved. The approach is based on a twodimensional polygon clipper wh ..."
Abstract

Cited by 87 (0 self)
 Add to MetaCart
(Show Context)
A polygon hidden surface and hidden line removal algorithm is presented. The algorithm recursively subdivides the image into polygon shaped windows until the depth order within the window is found. Accuracy of the input data is preserved. The approach is based on a twodimensional polygon clipper which is sufficiently general to clip a concave polygon with holes to the borders of a concave polygon with holes. A major advantage of the algorithm is that the polygon form of the output is the same as the polygon form of the input. This allows entering previously calculated images to the system for further processing. Shadow casting may then be performed by first producing a hidden surface removed view from the vantage point of the light source and then resubmitting these tagged polygons for hidden surface removal from the position of the observer. Planar surface detail also becomes easy to represent without increasing the complexity of the hidden surface problem. Translucency is also possible. Calculation times are primarily related to the visible complexity of the final image, but can range from a linear to an exponential relationship with the number of input polygons depending on the particular environment portrayed. To avoid excessive computation time, the implementation uses a screen area subdivision preprocessor to create several windows, each containing a specified number of polygons. The hidden surface algorithm is applied to each of these windows separately. This technique avoids the difficulties of subdividing by screen area down to the screen resolution level while maintaining the advantages of the polygon area sort method.
Pipeline Rendering: Interaction And Realism Through HardwareBased MultiPass Rendering
, 1996
"... ..."
Sorting and Hardware Assisted Rendering for Volume Visualization
 Symposium on Volume Visualization
, 1994
"... We present some techniques for volume rendering unstructured data. Colors and opacities are interpolated between vertices using hardware assisted texture mapping. We also present an O(n 2 ) method for sorting n arbitrarily shaped convex polyhedra prior to visualization. It generalizes the Newel ..."
Abstract

Cited by 68 (6 self)
 Add to MetaCart
We present some techniques for volume rendering unstructured data. Colors and opacities are interpolated between vertices using hardware assisted texture mapping. We also present an O(n 2 ) method for sorting n arbitrarily shaped convex polyhedra prior to visualization. It generalizes the Newell, Newell and Sancha sort for polygons to 3D volume elements. Introduction Tuchman, without artifacts due to linear approximation of the nonlinear opacity effects. This project grew out of the need to visualize unstructured meshed vector fields such as those found in existing finite element modeling code. Some volume rendering applications do not require more than one color. However, we have developed a visualization tool for rendering multicolored elements, such as colored flow volumes in a vector field, using an implementation of the ShirleyTuchman [1] algorithm. While monochromatic elements can be composited in any order as shown by [2], data sets containing many colors must be com...
A high accuracy volume renderer for unstructured data.
 IEEE Transactions on Visualization and Computer Graphics
, 1998
"... ..."
(Show Context)
Hardwareassisted visibility sorting for unstructured volume rendering
 IEEE Transactions on Visualization and Computer Graphics
, 2005
"... Abstract—Harvesting the power of modern graphics hardware to solve the complex problem of realtime rendering of large unstructured meshes is a major research goal in the volume visualization community. While, for regular grids, texturebased techniques are wellsuited for current GPUs, the steps ne ..."
Abstract

Cited by 54 (11 self)
 Add to MetaCart
(Show Context)
Abstract—Harvesting the power of modern graphics hardware to solve the complex problem of realtime rendering of large unstructured meshes is a major research goal in the volume visualization community. While, for regular grids, texturebased techniques are wellsuited for current GPUs, the steps necessary for rendering unstructured meshes are not so easily mapped to current hardware. We propose a novel volume rendering technique that simplifies the CPUbased processing and shifts much of the sorting burden to the GPU, where it can be performed more efficiently. Our hardwareassisted visibility sorting algorithm is a hybrid technique that operates in both objectspace and imagespace. In objectspace, the algorithm performs a partial sort of the 3D primitives in preparation for rasterization. The goal of the partial sort is to create a list of primitives that generate fragments in nearly sorted order. In imagespace, the fragment stream is incrementally sorted using a fixeddepth sorting network. In our algorithm, the objectspace work is performed by the CPU and the fragmentlevel sorting is done completely on the GPU. A prototype implementation of the algorithm demonstrates that the fragmentlevel sorting achieves rendering rates of between one and six million tetrahedral cells per second on an ATI Radeon 9800. Index Terms—Volume visualization, graphics processors, visibility sorting. 1
Constructive Volume Geometry
 Computer Graphics Forum
, 2000
"... We present an algebraic framework, called Constructive Volume Geometry (CVG), for modelling complex spatial objects using combinational operations. By utilising scalar fields as fundamental building blocks, CVG provides highlevel algebraic representations of objects that are defined mathematically ..."
Abstract

Cited by 47 (17 self)
 Add to MetaCart
We present an algebraic framework, called Constructive Volume Geometry (CVG), for modelling complex spatial objects using combinational operations. By utilising scalar fields as fundamental building blocks, CVG provides highlevel algebraic representations of objects that are defined mathematically or built upon sampled or simulated datasets. It models amorphous phenomena as well as solid objects, and describes the interior as well as the exterior of objects. We also describe a hierarchical representation scheme for CVG, and a direct rendering method with a new approach for consistent sampling. The work has demonstrated the feasibility of combining a variety of graphics data types in a coherent modelling scheme.
An Exact Interactive Time Visibility Ordering Algorithm for Polyhedral Cell Complexes
, 1998
"... A visibility ordering of a set of objects, from a given viewpoint, is a total order on the objects such that if object a obstructs object b,thenb precedes a in the ordering. Such orderings are extremely useful for rendering volumetric data. We present an algorithm that generates a visibility orderin ..."
Abstract

Cited by 44 (14 self)
 Add to MetaCart
A visibility ordering of a set of objects, from a given viewpoint, is a total order on the objects such that if object a obstructs object b,thenb precedes a in the ordering. Such orderings are extremely useful for rendering volumetric data. We present an algorithm that generates a visibility ordering of the cells of an unstructured mesh, provided that the cells are convex polyhedra and nonintersecting, and that the visibility ordering graph does not contain cycles. The overall mesh may be nonconvex and it may have disconnected components. Our technique employs the sweep paradigm to determine an ordering between pairs of exterior (mesh boundary) cells which can obstruct one another. It then builds on Williams' MPVO algorithm [33] which exploits the ordering implied by adjacencies within the mesh. The partial ordering of the exterior cells found by sweeping is used to augment the DAG created in Phase II of the MPVO algorithm. Our method thus removes the assumption of the MPVO algorithm t...