Real-time Rendering and Animation of Vegetation

Information

• Publication Type: PhD-Thesis
• Workgroup(s)/Project(s):
  • TreeLumination
• Date: February 2009
• Date (Start): May 2005
• Date (End): March 2009
• Second Supervisor: Oliver Deussen
• Rigorosum: 6. March 2009
• First Supervisor: Michael Wimmer
• Keywords: Animation, Real-time Rendering, Vegetation

Abstract

Vegetation rendering and animation in real-time applications still pose a significant problem due to the inherent complexity of plants. Both the high geometric complexity and intricate light transport require specialized techniques to achieve high-quality rendering of vegetation in real time. This thesis presents new algorithms that address various areas of both vegetation rendering and animation.

For grass rendering, an efficient algorithm to display dense and short grass is introduced. In contrast to previous methods, the new approach is based on ray tracing to avoid the massive overdraw of billboard or explicit geometry representation techniques, achieving independence of the complexity of the grass without losing the visual characteristics of grass such as parallax and occlusion effects as the viewpoint moves.

Also, a method to efficiently render leaves is introduced. Leaves exhibit a complex light transport behavior due to subsurface scattering and special attention is given to the translucency of leaves, an integral part of leaf shading. The light transport through a leaf is precomputed and can be easily evaluated at runtime, making it possible to shade a massive amount of leaves while including the effects that occur due to the leaf structure such as varying albedo and thickness variations or self shadowing.

To animate a tree, a novel deformation method based on a structural mechanics model that incorporates the important physical properties of branches is introduced. This model does not require the branches to be segmented by joints as other methods, achieving smooth and accurate bending, and can be executed fully on a GPU. To drive this deformation, an optimized spectral approach that also incorporates the physical properties of branches is used. This allows animating a highly detailed tree with thousands of branches and ten thousands of leaves efficiently.

Additionally, a method to use dynamic skylight models in spherical harmonics precomputed radiance transfer techniques is introduced, allowing to change the skylight parameters in real time at no considerable cost and memory footprint.

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BibTeX

@phdthesis{Habel_2009_PhD,
  title =      "Real-time Rendering and Animation of Vegetation",
  author =     "Ralf Habel",
  year =       "2009",
  abstract =   "Vegetation rendering and animation in real-time applications
               still pose a significant problem due to the inherent
               complexity of plants. Both the high geometric complexity and
               intricate light transport require specialized techniques to
               achieve high-quality rendering of vegetation in real time.
               This thesis presents new algorithms that address various
               areas of both vegetation rendering and animation.  For grass
               rendering, an efficient algorithm to display dense and short
               grass is introduced. In contrast to previous methods, the
               new approach is based on ray tracing to avoid the massive
               overdraw of billboard or explicit geometry representation
               techniques, achieving independence of the complexity of the
               grass without losing the visual characteristics of grass
               such as parallax and occlusion effects as the viewpoint
               moves.  Also, a method to efficiently render leaves is
               introduced. Leaves exhibit a complex light transport
               behavior due to subsurface scattering and special attention
               is given to the translucency of leaves, an integral part of
               leaf shading. The light transport through a leaf is
               precomputed and can be easily evaluated at runtime, making
               it possible to shade a massive amount of leaves while
               including the effects that occur due to the leaf structure
               such as varying albedo and thickness variations or self
               shadowing.  To animate a tree, a novel deformation method
               based on a structural mechanics model that incorporates the
               important physical properties of branches is introduced.
               This model does not require the branches to be segmented by
               joints as other methods, achieving smooth and accurate
               bending, and can be executed fully on a GPU. To drive this
               deformation, an optimized spectral approach that also
               incorporates the physical properties of branches is used.
               This allows animating a highly detailed tree with thousands
               of branches and ten thousands of leaves efficiently. 
               Additionally, a method to use dynamic skylight models in
               spherical harmonics precomputed radiance transfer techniques
               is introduced, allowing to change the skylight parameters in
               real time at no considerable cost and memory footprint.",
  month =      feb,
  address =    "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria",
  school =     "Institute of Computer Graphics and Algorithms, Vienna
               University of Technology ",
  keywords =   "Animation, Real-time Rendering, Vegetation",
  URL =        "https://www.cg.tuwien.ac.at/research/publications/2009/Habel_2009_PhD/",
}