Soft Shadow Mapping Research Articles

Revectorization‐Based Soft Shadow Mapping

AbstractIn this paper, we present revectorization‐based soft shadow mapping, an algorithm that enables the rendering of visually plausible anti‐aliased soft shadows in real time. In revectorization‐based shadow mapping, shadow silhouettes are anti‐aliased and filtered on the basis of a discontinuity space. By replacing the filtering step of the theoretical framework of the percentage‐closer soft shadow algorithm by a revectorization‐based filtering algorithm, we are able to provide anti‐aliasing mainly for near contact shadows or small penumbra sizes generated from low‐resolution shadow maps. Moreover, we present a screen‐space variant of our technique that generates visually plausible soft shadows with an overhead of only in processing time, when compared to the fastest soft shadow algorithms proposed in the literature, but that introduces shadow overestimation artefacts in the final rendering.

Multi-Resolution Rendering for Computationally Expensive Lighting Effects

Many lighting methods used in computer graphics such as indirect illumination can have very high computational costs and need to be approximated for real-time applications. These costs can be reduced by means of upsampling techniques which tend to introduce artifacts and affect the visual quality of the rendered image. This paper suggests a versatile approach for accelerating the rendering of screen space methods while maintaining the visual quality. This is achieved by exploiting the low frequency nature of many of these illumination methods and the geometrical continuity of the scene. First the screen space is dynamically divided into separate sub-images, then the illumination is rendered for each sub-image in an adequate resolution and finally the sub-images are put together in order to compose the final image. Therefore we identify edges in the scene and generate masks precisely specifying which part of the image is included in which sub-image. The masks therefore determine which part of the image is rendered in which resolution. A step wise upsampling and merging process then allows optically soft transitions between the different resolution levels. For this paper, the introduced multi-resolution rendering method was implemented and tested on three commonly used lighting methods. These are screen space ambient occlusion, soft shadow mapping and screen space global illumination.

An Efficient Soft Shadow Mapping for Area Lights in Various Shapes and Colors

An Efficient Soft Shadow Mapping for Area Lights in Various Shapes and Colors

Stochastic Soft Shadow Mapping

AbstractIn this paper, we extend the concept of pre‐filtered shadow mapping to stochastic rasterization, enabling real‐time rendering of soft shadows from planar area lights. Most existing soft shadow mapping methods lose important visibility information by relying on pinhole renderings from an area light source, providing plausible results only for small light sources. Since we sample the entire 4D shadow light field stochastically, we are able to closely approximate shadows of large area lights as well. In order to efficiently reconstruct smooth shadows from this sparse data, we exploit the analogy of soft shadow computation to rendering defocus blur, and introduce a multiplane pre‐filtering algorithm. We demonstrate how existing pre‐filterable approximations of the visibility function, such as variance shadow mapping, can be extended to four dimensions within our framework.

Efficient Screen Space Anisotropic Blurred Soft Shadows

Shadow mapping is an efficient method to generate shadows in real time computer graphics and has broad variations from hard to soft shadow synthesis. Soft shadowing based on shadow mapping is a blurring technique on a shadow map or on screen space. Blurring on screen space has an advantage for efficient sampling on a shadow map, since the blurred target array has exactly the same coordinates as the screen. However, a previous blurring method on screen space has a drawback: the generated shadow is not correct when a view direction has a large angle to the normal of the shadowed plane. In this paper, we introduce a new screen space based method for soft shadowing that is fast and generates soft shadows more accurately than the previous screen space soft shadow mapping method. The resultant images show shadows produced by our method just stand in the same place, while shadows by the previous method change in terms of penumbra while the view moves. Surprisingly, although our method is more complex than the previous method, the measurement results of the calculation time show our method is almost the same performance. This is because it controls the blurring area more accurately and thus successfully reduces multiplications for blurring.

Variance Soft Shadow Mapping

AbstractWe present variance soft shadow mapping (VSSM) for rendering plausible soft shadow in real‐time. VSSM is based on the theoretical framework of percentage‐closer soft shadows (PCSS) and exploits recent advances in variance shadow mapping (VSM). Our new formulation allows for the efficient computation of (average) blocker distances, a common bottleneck in PCSS‐based methods. Furthermore, we avoid incorrectly lit pixels commonly encountered in VSM‐based methods by appropriately subdividing the filter kernel. We demonstrate that VSSM renders high‐quality soft shadows efficiently (usually over 100 fps) for complex scene settings. Its speed is at least one order of magnitude faster than PCSS for large penumbra.

Packet‐based Hierarchal Soft Shadow Mapping

AbstractRecent soft shadow mapping techniques based on back‐projection can render high quality soft shadows in real time. However, real time high quality rendering of large penumbrae is still challenging, especially when multilayer shadow maps are used to reduce single light sample silhouette artifact. In this paper, we present an efficient algorithm to attack this problem. We first present a GPU‐friendly packet‐based approach rendering a packet of neighboring pixels together to amortize the cost of computing visibility factors. Then, we propose a hierarchical technique to quickly locate the contour edges, further reducing the computation cost. At last, we suggest a multi‐view shadow map approach to reduce the single light sample artifact. We also demonstrate its higher image quality and higher efficiency compared to the existing depth peeling approaches.

Robust Soft Shadow Mapping with Backprojection and Depth Peeling

Soft shadow mapping is an attractive solution to the problem of realtime soft shadows because it works with any kind of rasterizable geometry (in particular alpha-transparent textures and hair), it does not require any precomputation, and it is simple to implement on the GPU. However, state-of-the-art approaches have several limitations that prevent them from being practical for all scenes. First, parameter tuning is required to avoid surface acne. Second, gaps between shadowmap pixels are either ignored, which results in light bleeding, or handled using gap filling, which results in overshadowing. We present a more robust soft shadow mapping technique, based on a recent backprojection algorithm, that uses depth peeling to address the problems of surface acne and light bleeding. Our algorithm uses a multi-layer shadow map to reduce light bleeding, and midpoint shadow maps to handle self-shadowing more robustly. It provides high-quality soft shadowing for complex scenes, while still maintaining interactive...

High‐Quality Adaptive Soft Shadow Mapping

Abstract The recent soft shadow mapping technique [GBP06] allows the rendering in real‐time of convincing soft shadows on complex and dynamic scenes using a single shadow map. While attractive, this method suffers from shadow overestimation and becomes both expensive and approximate when dealing with large penumbrae. This paper proposes new solutions removing these limitations and hence providing an efficient and practical technique for soft shadow generation. First, we propose a new visibility computation procedure based on the detection of occluder contours, that is more accurate and faster while reducing aliasing. Secondly, we present a shadow map multi‐resolution strategy keeping the computation complexity almost independent on the light size while maintaining high‐quality rendering. Finally, we propose a view‐dependent adaptive strategy, that automatically reduces the screen resolution in the region of large penumbrae, thus allowing us to keep very high frame rates in any situation.