It is important for the rapid visualization of large scale forest scene to dynamically simplify and recombine model data. In order to preserve the geometric features and visual perception of tree model, this paper presents a real-time information recombination method of complex 3D tree model based on visual perception. This method adopts visual attention model and the visual characteristic of tree structures, and then uses geometry-based and image-based methods to simplify tree models and construct a hybrid representation model. The hybrid representation model reflects the visual perception features of 3D tree models that can embody topological semantics in dynamic simulation. In addition, this method automatically extracts the representation information of 3D tree model based on visual perception, and recombines model information in real time according to the dynamic viewpoint of virtual scene. Finally, this method is applied in the simplification of different tree models, and it is compared with the existing tree model simplification methods. Experimental results show that this method can not only preserve better visual perception for 3D tree models, but also effectively decrease the geometric data of forest scene, and improve the rendering efficiency of forest scene.

Real-time information recombination of complex 3D tree model based on visual perception

The effectiveness of 3D tree model simplification techniques and their objective and subjective performance evaluations are examined in this work. The simplification techniques developed in [1, 2] were based on pixel-based metrics, which did not consider the tree model's leaf density. For performance improvement, we perform simplification based on the tree leaf density of rendered images viewed from multiple angles. Furthermore, objective performance analysis is conducted to evaluate how well different algorithms are able to simplify tree models that appear as close to the original tree model with a given budget on the number of tree leaves in the model. To this end, a performance metric based on the Gabor filter is developed to analyze the orientation and spatial relationship within the rendered tree models. Finally, subjective evaluation is conducted by a group of 23 people. Both the objective and the subject evaluations reach a consistent conclusion; namely, the newly proposed densitybased simplification technique offers the best results.

Enhanced 3d tree model simplification and perceptual analysis

Plants and trees are an essential part of outdoor scenes. They are represented by such a vast number of polygons that performing real-time visualization is still a problem in spite of the advantages of the hardware. Some methods have appeared to solve this drawback based on point- or image-based rendering. However, geometry representation is required in some interactive applications. This work presents a simplification method that deals with the geometry of the foliage, reducing the number of primitives that represent these objects and making their interactive visualization possible. It is based on an image-based simplification that establishes an order of leaf pruning and reduces the complexity of the canopies of trees and plants. The proposed simplification method is viewpoint-driven and uses the mutual information in order to choose the leaf to prune. Moreover, this simplification method avoids the pruned appearance of the tree that is usually produced when a foliage representation is formed by a reduced number of leaves. The error introduced every time a leaf is pruned is compensated for if the size of the nearest leaf is altered to preserve the leafy appearance of the foliage. Results demonstrate the good quality and time performance of the presented work.

Viewpoint-Driven Simplification of Plant and Tree Foliage.

For the rapid visualization of large-scale forest scene, this paper proposes a real-time recombination method of complex 3D tree model information. This method adopts visual attention model and the visual characteristic of tree structures, then uses geometry-based and image-based methods to simplify tree models and construct a hybrid representation model for the 3D tree models based on the visual perception. It reflects the visual perception features of 3D tree models that can embody topological semantics in dynamic simulation. Finally, the method in this paper is applied to the simplification of several tree models, and compared with some existing tree model simplification methods. The experimental results show that this method can not only preserve better visual perception of 3D tree models, but also effectively decrease the geometric data of the forest scene, and improve the rendering efficiency and real-time walkthrough speed of forest scene.

Real-time recombination method of complex 3d tree model information on visual perception preserving

We present a set of techniques to simplify tree models for faster rendering while retaining their visual resemblance to the original model. This goal is achieved by setting a budget constraint of how many leaves shall be rendered, and we select leaves with higher possibilities to be visible to generate a simplified model for rendering. We first examine how leaf objects can be prioritized to provide a tree model suitable for a single viewing angle. The camerapsilas projected screen space is partitioned into several small regions to ensure that each region is guaranteed to be filled with a certain number of leaves. Each region selects higher priority leaves by utilizing the leaf objectspsila spatial relationship to the camera. Then, an iterative algorithm is proposed to allocate leaf objects at different viewing angles. The algorithm chooses different viewing positions for leaf allocation at each iteration with the goal of maximizing the resemblance to the original tree model at all possible angles. Three criteria taken in consideration for viewing angle selection are: distance, leaf normal, and unfilled pixel. Experimental results are provided to demonstrate time efficiency of the proposed techniques at the cost of little visual degradation.

C.-C.J. Kuo

Papers

Fast and Flexible Tree Rendering with Enhanced Visibility Estimation