Partitioned Shadow Volumes (original) (raw)
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A comparison of three shadow volume algorithms
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.
ACM Transactions on Graphics, 2011
a) (b) (c) Figure 1: Images rendered with the novel shadow algorithm. All images rendered in 1024x1024, time taken to generate shadow buffers in parenthesis. (a) Pixel accurate hard shadows in a game scene (7.29ms, 60k triangles). (b) Alpha-textured shadow casters (13ms, 35k triangles). (c) Colored transparent shadows. Image rendered using depth peeling of 8 layers (75.66ms, 5-19 ms per layer, 60k triangles).
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 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 ...
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.
Practical and robust stenciled shadow volumes for hardware-accelerated rendering
Twenty-five years ago, Crow published the shadow volume approach for determining shadowed regions in a scene. A decade ago, Heidmann described a hardware-accelerated stencil bufferbased shadow volume algorithm. However, hardware-accelerated stenciled shadow volume techniques have not been widely adopted by 3D games and applications due in large part to the lack of robustness of described techniques. This situation persists despite widely available hardware support. Specifically what has been lacking is a technique that robustly handles various "hard" situations created by near or far plane clipping of shadow volumes.
Clustered Deep Shadow Maps for Integrated Polyhedral and Volume Rendering
Advances in Visual Computing, 2012
This paper presents a hardware-accelerated approach for shadow computation in scenes containing both complex volumetric objects and polyhedral models. Our system is the first hardware accelerated complete implementation of deep shadow maps, which unifies the computation of volumetric and geometric shadows. Up to now such unified computation was limited to software-only rendering. Previous hardware accelerated techniques can handle only geometric or only volumetric scenes-both resulting in the loss of important properties of the original concept. Our approach supports interactive rendering of polyhedrally bounded volumetric objects on the GPU based on ray casting. The ray casting can be conveniently used for both the shadow map computation and the rendering. We show how anti-aliased high-quality shadows are feasible in scenes composed of multiple overlapping translucent objects, and how sparse scenes can be handled efficiently using clustered deep shadow maps.
Stencil shadow volumes for complex and deformable objects
Proceedings of the 2004 11th IEEE International Conference on Electronics, Circuits and Systems, 2004. ICECS 2004., 2004
We present real-time shadow method based on the shadow volume that exploit capabilities of the modern graphics cards. Algorithm is primarily created for casting shadows of a highly concave complex objects such as trees. For those objects silhouette calculation that is usually preformed by other shadow volume algorithms is complicated and poorly justified. Instead of calculations, it is better to assume a worst case scenario and use all of the edges for construction of the shadow volume mesh, skipping silhouette determination entirely. The achieved benefit is that all procedure, the object and shadow calculation and rendering, could be done on GPU. Proposed solution for shadow casting allows open edges. Indexed vertex blending is used for shadow projections, and the only calculation required is determining projection matrices. Once created, shadow volume is treated like any other mesh.
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...