Per-triangle shadow volumes using a view-sample cluster hierarchy (original) (raw)
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The Visual Computer, 1992
This paper describes and compares three different approaches to computing shadows each based on the idea of shadow volumes, a basic algorithm, the Shadow Volume BSP Tree algorithm, and a third based on 2D space subdivision, Shadow Tiling. Binary Space Partition trees are used to organise the polygons in the scene in a frontto-back order from the point of view of the light source, and then shadows on a polygon are computed by clipping the polygon to the shadow volumes of polygons closer to the light source. The three algorithms differ in their approach to minimising the number of comparisons of a polygon with the shadow volumes of its predecessors, and one of the algorithms represents the total shadow volume itelf by a BSP tree. The algorithms are compared analytically and statistically.
Shadow volume BSP trees for computation of shadows in dynamic scenes
Proceedings of the 1995 symposium on …, 1995
This paper presents an algorithm for shadow calculation in dynamic polyhedral scenes illuminated by point light sources. It is based on a modi cation of Shadow Volume Binary Space Partition trees, to allow these be constructed from the original scene polygons in arbitrary order and to support for fast reconstruction after a change in scene geometry. Timings using sample scenes are presented that indicate substantial savings both in terms of computation time and shadows produced.
A Survey on Volume Shadows in Computer Graphics
This study will provide an overview of popular and famous algorithms and techniques in shadow generation based on shadow volumes. It characterizes well-known techniques, describing each of them in detail, and discusses the advantages and drawbacks of each. Basic ideas, improvements, and future works of the techniques are also comprehensively summarized and analyzed in depth. Often, programmers have difficulty selecting an appropriate shadow generation algorithm based on shadow volumes that is specific to their purpose. We have classified and systemized these techniques. The main goal of this paper is to provide researchers with background on a progress of shadow volume techniques so as to make it easier for researchers to choose the method best suited to their aims. It is also hoped that our analysis will help researchers find solutions to the shortcomings of each technique.
An Optimized Soft Shadow Volume Algorithm with Real-Time Performance
In this paper, we present several optimizations to our previously presented soft shadow volume algorithm. Our optimizations include tighter wedges, heavily optimized pixel shader code for both rectangular and spherical light sources, a frame buffer blending technique to overcome the limitation of 8-bit frame buffers, and a simple culling algorithm. These together give real-time performance, and for simple models we get frame rates of over 150 fps. For more complex models...
Real time volumetric shadows using polygonal light volumes
This paper presents a more efficient way of computing single scattering effects in homogeneous participating media for real-time purposes than the currently popular ray-marching based algorithms. These effects include halos around light sources, volumetric shadows and crepuscular rays. By displacing the vertices of a base mesh with the depths from a standard shadow map, we construct a polygonal mesh that encloses the volume of space that is directly illuminated by a light source. Using this volume we can calculate the airlight contribution for each pixel by considering only points along the eye-ray where shadow-transitions occur. Unlike previous ray-marching methods, our method calculates the exact airlight contribution, with respect to the shadow map resolution, at real time frame rates.
IEEE Computer Graphics and Applications, 2000
Essential to realistic and visually appealing images, shadows are difficult ta compute in most display environments. This survey characterizes the various types of shadows. It also describes most existing shadow algorithms and discusses their complexities, advantages, and shommings. We examine herd shadows, soft shadbws, shadows of transparent objects, and shadows for com-plex modeling primitives. For each type, we examine shadow algorithms within various rendswing techniques. This survey attempts to provide readem with enough background and insight on the various rmthods to d o w them to choose the algorithm best w p u i t e d to their W . We also hope that our analysis will h&p identify the a m that need more research and point bo possible sotutkms.
Compact precomputed voxelized shadows
ACM Transactions on Graphics, 2014
Figure 1: An example of using our algorithm to evaluate precomputed shadows from the sun when viewing the scene at varying scales. Our compact data structure occupies 100MB of graphics memory and is equivalent to a 256k×256k (i.e. 262144 2) shadow map. With a filter size of 9×9 taps, shadow evaluation is done in < 1ms at 1080p resolution.
Occlusion culling and z-fail for soft shadow volume algorithms
The Visual Computer, 2004
This paper presents a significant improvement of our previously proposed soft shadow volume algorithm for simulating soft shadows. By restructuring the algorithm, we can considerably simplify the computations, introduce efficient occlusion culling with speedups of 3-4 times, thus approaching real-time performance, and also generalize the algorithm to produce correct shadows even when the eye is inside a shadowed region (using z-fail). We present and evaluate a three pass implementation of the restructured algorithm for near real-time rendering of soft shadows on a computer with a commodity graphics accelerator. However, preferably the rendering of the wedges should be implemented in hardware, and for this we suggest and evaluate a single pass algorithm.
A geometry-based soft shadow volume algorithm using graphics hardware
ACM Transactions on Graphics, 2003
Most previous soft shadow algorithms have either suffered from aliasing, been too slow, or could only use a limited set of shadow casters and/or receivers. Therefore, we present a strengthened soft shadow volume algorithm that deals with these problems. Our critical improvements include robust penumbra wedge construction, geometry-based visibility computation, and also simplified computation through a four-dimensional texture lookup. This enables us to implement the algorithm using programmable graphics hardware, and it results in images that most often are indistinguishable from images created as the average of 1024 hard shadow images. Furthermore, our algorithm can use both arbitrary shadow casters and receivers. Also, one version of our algorithm completely avoids sampling artifacts which is rare for soft shadow algorithms. As a bonus, the four-dimensional texture lookup allows for small textured light sources, and, even video textures can be used as light sources. Our algorithm ...