Real-time animation of vegetation : novel 2D approach and interactive authoring interface

• Main Author: Chen, Kan
• Other Authors: Alexei Sourin
• Format: Theses and Dissertations
• Language: English
• Published: 2017
• Subjects: DRNTU::Engineering::Computer science and engineering::Computing methodologies::Computer graphics
• Online Access: http://hdl.handle.net/10356/69490
• Institution: Nanyang Technological University

Real-time animation of vegetation (a field of plants), e.g., grass, shrubs, and trees, has many applications such as in movies, cartoons, and games. However, animating a vegetation scene is a challenging problem, because in general a vegetation scene has complex geometry and may consist of large quantity of elements (grass blades, leaves etc.). The conventional method of manual drawing (e.g., 2D cartoons) or setting poses of plants at many key frames (e.g., 3D animation movies) requires tedious work and art skills. Physics-based methods can achieve physically realistic animation, but they require high computational costs and lack intuitive direct control. This thesis presents novel algorithms to efficiently animate vegetation in 2D images and 3D scenes in real-time as well as provide users with an intuitive interface to easily and rapidly design and generate animation of short plants. This work focuses on modeling the motions of plants under the influence of external forces, e.g., natural wind and passing object. Based on observations, vegetation elements may stick together and move in groups, exhibiting harmonic motion effects such as deforming and oscillating. To realize these effects, a real-time method has been proposed, which combines fluid simulation, wave simulation, and grid-based image warping to simulate harmonic motions of vegetation in 2D images, in particular cartoon style images. For real-time 3D applications such as games, it is important to lower the computational cost of vegetation animation while still making the animation looks visually plausible. Therefore, an efficient 2D-based approach for real-time animation of vegetation in 3D scenes has been proposed, especially suitable for vegetation with densely leaved foliage. This approach represents vegetation as view-dependent 2D billboard layers, adopts the proposed 2D harmonic motion simulation for modeling the dynamics of vegetation at the first layer (closest to the viewer), and utilizes this dynamics to guide the animation of the rest of the layers while addressing the motion effects in depth and occlusion effects. Lastly, short plants, such as grass, flowers, and shrubs, are common vegetation species. It is not always easy or intuitive for users to generate their desired motions of short plants using existing methods. Thus, a novel approach to author the common motions of short plants which are bending and twisting has been proposed. It is based on the observation that hand motions can represent the bending and twisting motions of short plants and using hand to describe motions is natural and proficient for human. Therefore, a hand is used as a `puppet' to author the animation of one single short plant. First, the global motions of the short plant are authored, followed by the motions of its elements such as leaves. A framework to utilize the animation results to animate a field of short plants has also been proposed. Using the proposed methods, the manual efforts of animators and the computational costs can be significantly reduced, and natural-looking vegetation animation (comparable with real videos, cartoons, and the results using existing commercial software) can be achieved. The proposed 2D method can be applied to enhance vegetation photographs or paintings with animated vegetation motions as well as to help animators to create cartoon animations of vegetation. Additionally, this method can be incorporated with haptic interaction to provide users with a multisensory experience with images. The proposed 3D animation method allows dense vegetation scenes to be animated in real-time applications. The proposed animation authoring method empowers users to intuitively and rapidly author and generate their desired motions of short plants.