| 1. |
- Billeter, Markus, 1984, et al.
(author)
-
Real-Time Multiple Scattering using Light Propagation Volumes
- 2012
-
In: Proceedings - I3D 2012: ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games. 2012 16th ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games, I3D 2012, Costa Mesa, CA, 9-11 March 2012. - New York, NY, USA : ACM. - 9781450311946 ; , s. 119-126
-
Conference paper (peer-reviewed)abstract
- This paper introduces a new GPU-based, real-time method for rendering volumetric lighting effects produced by scattering in a participating medium. The method includes support for indirect illumination by scattered light, high-quality single-scattered volumetric shadows, and approximate multiple scattered volumetric lighting effects in isotropic and homogeneous media. The method builds upon an improved propagation scheme for light propagation volumes. This scheme models scattering according to the radiative light transfer equation during propagation. The initial state of the light propagation volumes is based on single-scattered light identified with shadow maps; this allows generation of a high quality initial distribution of radiance. After propagation, the resulting distribution is used as a source of diffuse light during rendering and is also ray marched for volumetric effects from multiple scattering. Volumetric shadows from single-scattered light are rendered separately. We compare the new method to single-scattered volumetric shadows produced by contemporary techniques, plain light propagation volumes (which this new method extends), and a simple composition thereof.
|
|
| 2. |
- Olsson, Ola, 1976, et al.
(author)
-
Clustered Deferred and Forward Shading
- 2012
-
In: HPG '12: Proceedings of the Conference on High Performance Graphics 2012. - 2079-8679. - 9783905674415 ; , s. 87-96
-
Conference paper (peer-reviewed)abstract
- This paper presents and investigates Clustered Shading for deferred and forward rendering. In Clustered Shading, view samples with similar properties (e.g. 3D-position and/or normal) are grouped into clusters. This is comparable to tiled shading, where view samples are grouped into tiles based on 2D-position only. We show that Clustered Shading creates a better mapping of light sources to view samples than tiled shading, resulting in a significant reduction of lighting computations during shading. Additionally, Clustered Shading enables using normal information to perform per-cluster back-face culling of lights, again reducing the number of lighting computations. We also show that Clustered Shading not only outperforms tiled shading in many scenes, but also exhibits better worst case behaviour under tricky conditions (e.g. when looking at high-frequency geometry with large discontinuities in depth). Additionally, Clustered Shading enables real-time scenes with two to three orders of magnitudes more lights than previously feasible (up to around one million light sources).
|
|
| 3. |
- Olsson, Ola, 1976, et al.
(author)
-
Tiled and clustered forward shading: supporting transparency and MSAA
- 2012
-
In: SIGGRAPH '12: SPECIAL INTEREST GROUP ON COMPUTER GRAPHICS AND INTERACTIVE TECHNIQUES CONFERENCE. - New York, New York, USA : ACM Press. - 9781450316835 ; , s. 37:1-
-
Conference paper (peer-reviewed)abstract
- We present details of Tiled and Clustered Forward Shading in its application to rendering transparent geometry and using Multi Sampling Anti Aliasing (MSAA). We detail how transparency and MSAA is supported, and present performance results measured on modern GPUs.Previous techniques for handling large numbers of lights are usually based on deferred shading [Andersson 2009; Lauritzen 2010]. However, deferred shading techniques struggle with impractically large frame buffers when MSAA is used, and make supporting transparency difficult. In addition, deferred shading makes it more difficult to support custom shaders on geometry.Tiled Forward Shading is a new and highly practical approach to real-time shading scenes with thousands of light sources, introduced by Olsson and Assarsson in 2011 [2011]. Their results, measured on an GTX 280 GPU, indicated that tiled forward shading was impractically slow. Performance on more recent GPUs has improved considerably (approaching that of tiled deferred), which opens up the possibility of using the technique to support transparency and MSAA.Clustered Shading further extends tiled shading by adding depth partitioning [Olsson et al. 2012]. We show how Clustered Forward Shading can be extended to support transparency efficiently.Forward shading naturally supports both transparency and MSAA, which has been shown in previous work. However, the performance and implementation details have not previously been investigated.We provide details on how to construct the light grid for use with transparency. When the transparent geometry is considered, the depth range optimization cannot be fully used. Instead, only a more conventional hierarchical depth test can be used. The grid structure can be built once, and quickly pruned to prepare a more efficient instance for opaque geometry. However, as each transparent layer must consider all the lights in the tile, performance does not scale linearly with the depth complexity, but far worse (Figure 1, right).To improve on this we extend clustered forward shading by constructing the grid using a pre-pass over all geometry (not just opaque), and flagging clusters as a side effect. This allows us to quickly find the unique clusters used. As clusters contain only space around actual samples that need shading, efficiency is much better (Figure 1, left).For deferred shading a single 1080p, 16x MSAA, 16-bit float RGBA buffer requires over 250Mb of memory. In addition, each sample may need to be shaded individually, effectively running shading at a per-sample frequency. For forward shading, no G-Buffers are required and MSAA is trivially enabled.A brief performance and memory comparison is shown in Figure 2, showing that clustered forward outperforms tiled forward by more than 2 times, and also outperforms tiled deferred, if MSAA is used.
|
|
