Robust Silhouette Shadow Volumes on Contemporary Hardware (original) (raw)
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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.
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 ...
Fast and Robust Tessellation-Based Silhouette Shadows
2014
Figure 1: The image shows the transformation of a quad into three overlapping shadow volume sides. The transition from part a) to part b) is tessellation of quad with Multiplicity = 3. Only green and blue triangles will be drawn. Yellow and gray triangles will be degenerated. The transition from part b) over part c) to part d) shows degeneration process. Red and purple vertices 3, 4 and 7, 8 from part a) form only one vertex in part d). The transition from part d) to part e) shows rotation around red and purple vertices. This transformation creates three overlapping sides of shadow volume. Positions of vertices A, B, C, D that form initial quad, can be computed according to equations 2. ABSTRACT
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).
A real-time shadow approach for an augmented reality application using shadow volumes
2003
Abstract Shadows add a level of realism to a rendered image. Moreover, they are used as visual clues to determine spacial relationships and real-time shadows will gain importance in current real-time computer graphics applications for this reason. Twenty-five years ago, Crow published the shadow volume approach for determining shadowed regions of a scene. In this paper we present a modified real-time shadow volume algorithm that can be used in an Augmented/Mixed Reality application.
Soft shadow volumes for ray tracing
ACM Transactions on Graphics, 2005
We present a new, fast algorithm for rendering physically-based soft shadows in ray tracing-based renderers. Our method replaces the hundreds of shadow rays commonly used in stochastic ray tracers with a single shadow ray and a local reconstruction of the visibility function. Compared to tracing the shadow rays, our algorithm produces exactly the same image while executing one to two orders of magnitude faster in the test scenes used. Our first contribution is a two-stage method for quickly determining the silhouette edges that overlap an area light source, as seen from the point to be shaded. Secondly, we show that these partial silhouettes of occluders, along with a single shadow ray, are sufficient for reconstructing the visibility function between the point and the light source.
New Silhouette Detection Algorithm to Create Real-Time Volume Shadow
2011 Workshop on Digital Media and Digital …, 2011
This paper introduced new real-time application for outdoor computer graphic programming to control the amount of shadow with effect of sun's position. The position of sun plays an important rule for outdoor games. Calculation of sun's position, as a result, position and length of shadows require a lot of attention and preciseness. Julian dating is used to calculate the sun's position in the virtual dome. In addition, of computer graphics, building design is another field that this paper contributes on it. To create shadow, projection shadow is proposed. By calculating the sun's position in the specific date, time and location on the earth, shadow is generated. Length and angle of shadow are two parameters measured for building designers and both of them are calculated in this proposed real-time application. Therefore, it can be used for teachers to teach some part of physics about earth orbit and effect of sun on shadow and it can be used in building design and commercial games in virtual reality systems.