A Method of Optimizing Terrain Rendering Using Digital Terrain Analysis

Terrain rendering is an important issue in Geographic Information Systems and other fields. During large-scale, real-time terrain rendering, complex terrain structure and an increasing amount of data decrease the smoothness of terrain rendering. Existing rendering methods rarely use the features of terrain to optimize terrain rendering. This paper presents a method to increase rendering performance through precomputing roughness and self-occlusion information making use of GIS-based Digital Terrain Analysis. Our method is based on GPU tessellation. We use quadtrees to manage patches and take surface roughness in Digital Terrain Analysis as a factor of Levels of Detail (LOD) selection. Before rendering, we first regularly partition the terrain scene into view cells. Then, for each cell, we calculate its potential visible patch set (PVPS) using a visibility analysis algorithm. After that, A PVPS Image Pyramid is built, and each LOD level has its corresponding PVPS. The PVPS Image Pyramid is stored on a disk and is read into RAM before rendering. Based on the PVPS Image Pyramid and the viewpoint’s position, invisible terrain areas that are not culled through view frustum culling can be dynamically culled. We use Digital Elevation Model (DEM) elevation data of a square area in Henan Province to verify the effectiveness of this method. The experiments show that this method can increase the frame rate compared with other methods, especially for lower camera flight heights.

Level of detail parent and dynamic culling scheme for flight simulator

Background/Objectives: Due to huge volume of data, it is required to reduce the number of vertices in flight simulator through level of detail and culling. However, it is required to integrate them accordingly.Methods/Statistical analysis: Due to high point of view, terrain data in wide area are usually rendered in the flight simulator. So, conservational level of detail and culling schemes have adaptation problem in flight simulator. To defeat this problem, dynamic culling scheme and level of detail parent method based on line of sight are proposed.Findings: Experiment scenarios are built to measure and compare the frame per second and number of vertices in four separate schemes, that is, scheme without the proposed algorithm, applying view frustum culling and applying culling and level of detail together and graphic processing unit based parallel processing algorithm, respectively. The proposed scheme reveals the similar values in the case of small-volume of terrain data. On the other hand, frame per second is significantly improved in huge volume of terrain data by reducing the number of vertices through dynamic culling and level of detail parent method. Specially, when level of detail parent method is applied to rendering the city with large number of buildings, the proposed scheme reveals the best frame per second among the comparative schemes.Improvements/Applications: Improved rendering algorithm was proposed to handle huge volume of terrain data and thereby to prove the applicability of the proposed scheme in other simulator.

Galactica, a Digital Planetarium for Immersive Virtual Reality Settings

The authors describe a new Digital Planetarium system and application (“Galactica”), for interactive visualization of astrophysical data and phenomena in immersive virtual reality (VR) settings, based in OpenSceneGraph (OSG). Galactica enables a visual and aural experience of a virtual space traveler, that can go anywhere in the Solar System and the Milky Way at any speed. The application was tested with an available dataset of such scenery, featuring 100 629 textured billboards representing stars and additional 104 328 polygons, representing constellations, orbits, planets and respective moons of the Solar System. The authors have computed the frame rate, GPU traverse time, Cull traverse time and Draw traverse time for three visualization conditions: (A) standard OSG view frustum culling technique; (B) view frustum culling with an octree organization of the scene; (C) view frustum culling with same organization of the scene and the occlusion culling algorithm. They have generally concluded that their acceleration techniques out-performs the standard OSG view frustum culling for the mentioned metrics, when around half or less than half of the dataset is in view of the virtual camera.

AN IMPROVED VIEW FRUSTUM CULLING METHOD USING OCTREES FOR 3D REAL-TIME RENDERING

The generation of real-time 3D graphics scenes normally demands high computational requirements. Several applications can benefit from efficient algorithms for rendering complex virtual environments, such as computer games, terrain visualization, virtual reality and visual simulation. This paper describes an improved view frustum culling method using spatial partitioning based on octrees for 3D real-time rendering. The proposed method is compared against two other approaches. Experiments using four different scenes are conducted to evaluate the performance of each tested method. Results demonstrate that the proposed method presents superior frame rate for all scenes.

Interactive Rendering of Indoor and Urban Environments on Handheld Devices by Combining Visibility Algorithms with Spatial Data Structures

This work presents a comparative study of various combinations of visibility algorithms (view-frustum culling, backface culling, and a simple yet fast algorithm called conservative backface culling) and different settings of standard spatial data structures (non-uniform Grids, BSP-Trees, Octrees, and Portal-Octrees) for enabling efficient graphics rendering of both indoor and urban 3D environments, especially suited for low-end handheld devices. Performance tests and analyses were conducted using two different mobile platforms and environments in the order of thousands of triangles. The authors demonstrate that navigation at interactive frame rates can be obtained using geometry rather than image-based rendering or point-based rendering on the cell phone Nokia n82.

Interactive Rendering of Indoor and Urban Environments on Handheld Devices by Combining Visibility Algorithms with Spatial Data Structures

This work presents a comparative study of various combinations of visibility algorithms (view-frustum culling, backface culling, and a simple yet fast algorithm called conservative backface culling) and different settings of standard spatial data structures (non-uniform Grids, BSP-Trees, Octrees, and Portal-Octrees) for enabling efficient graphics rendering of both indoor and urban 3D environments, especially suited for low-end handheld devices. Performance tests and analyses were conducted using two different mobile platforms and environments in the order of thousands of triangles. The authors demonstrate that navigation at interactive frame rates can be obtained using geometry rather than image-based rendering or point-based rendering on the cell phone Nokia n82.