1. Hierarchical and Dynamic Large-Scale Railway-Track Modeling Method for High-Speed Train Real-Time Visual Simulation
Good afternoon, first of all, let me introduce myself.
My name is Shi-Jian Liu from Fujian University of Technology
Today I’d like to present our work, which is a modeling method of railway-track for Visual simulation.
Shi-Jian Liu1,2, Jeng-Shyang Pan1,2, Zheng Zou3, Bei-Ji Zou3 and Sheng-Hui Liao3
1Shcool of Information Science and Engineering
2Key Laboratory of Big Data Mining and Applications of Fujian Province
Fujian University of Technology
3Shcool of Information Science and Engineering
Central South University

2. Outlines 1. Introduction 2. Challenges & Related Works
3. Our method & Results
4. Conclusion & Future Works

3. Outlines 1. Introduction 2. Challenges & Related Works
3. Our method & Results
4. Conclusion & Future Works

4. Visual Simulations The Visual simulation is a little bit like VR.
The virtual scenes are projected and visualized on a large screen during the simulation
in the purpose of different demonstration.
For example, the project of ours is to demonstrate different states of high-speed train running on specific track,
Which can be used to train the drivers, or test for the simulated traction data in an intuitive way.

5. Actually, two graphic workstations and projectors are used in the project.
In order to produce 3D experience like watching the 3D movie in the cinema.

6. Outlines 1. Introduction 2. Challenges & Related Works
3. Our method & Results
4. Conclusion & Future Works

7. Challenges Large-scale scene Real-time rendering (≥30 fps)
modeling & management
Real-time rendering (≥30 fps)
Drawing,
Culling,
User Interaction
and other Program Actions
Visual Simulation versus Cartoon Films
Keep the frame rate
Real-time feedback
The challenges of this work include that
Firstly, there are large-scale scene should be present in the simulation,
Therefore, how to modeling the scene data and manage then efficiently are crucial to the system.
Secondly, in order to have a good user experience, the scene image should be rendered no less than 30 frame/second.
Furthermore, unlike cartoon films, the visual simulation is a real-time system,
Which allows user to interact with it and offer feedback in real-time.
In other words, they can be treated like online and offline system respectively.

8. Scene Railway track Models to be rendered Terrain Train
Trees, Buildings, …
Railway track …
The scene objects of the project including terrain, high-speed train and so on
While, in this work, we focus on the railway-track as depicted in the picture, which is a large-scale object generally.
For example, the distance of high-speed railway from Beijing to Shanghai is more than 1000 kilometers.

9. Approaches for modeling
3DS MAX / Multigen Creator
Small delicate models
Manual operation
Programming
Automatic one based on an algorithm or mathematical expression
Strategy to decompose the models
Approaches popularly used to generate the railway models can be categorized as manual and automatic methods.
Both of them have some advantages and drawbacks for our case.

10. Outlines 1. Introduction 2. Challenges & Related Works
3. Our method & Results
4. Conclusion & Future Works

11. Railway track a series of connected line sections
curved section
linear section
this paper proposes a novel bottom-up solution,
which considers the entire railway-track as the combination of multiple hierarchical models:
Namely the linear and curved ones.
In the view of track centre line

12. Our Method Combine the manual and automatic techniques together
Manual operation
Off-line modeling of repeated geometric structure of track
Automatic operation
On-line assembling of Element models
This method takes the advantages of manual and automatic method,
Specifically, small repeated geometric structure of the track will be off-line manual generated
and on-line assembled to form an integrated railway-track.

13. Data given by ID Type Origin(m) End(m) Curve Radius(m) … 3 Left curve
3014
4015
1000 4
Straight line
5664
NULL 5
Right curve
6323
3500 6
7593
Our method works based on the fact that
A specific railway-track can be described by its central line, which is available from CSR.
It can be divided into segments according to the type, i.e. the linear or curved one.

14. Statistics & Classification
Straight lines
One
Curves
1 ≤ Cluster ≤ 16
Curve Radius (m)
400
460
800
2200
2500
3500
4000
4500
count 1 2
5500
7000
8000
9000
10000
11000
12000
14000 19 29 49 54 13 21 6
3. Though there are many segments in a railway track,
The linear and curved segments can be classified into some categories, and the number of categories are limited.
4. Segment of a particular category can be divided into smaller components, which is named as element by us.

15. Element  Section  Railway
Therefore, once the element models are produced by experts,
The specific railway-track can be assembled hierarchically,

16. Scheme of the method Off-line phase On-line phase Definition
Manual modeling
On-line phase
Parameter calculation
Assembling
As mentioned before, our scheme consist of two phase.

17. Track elements modeling
Define
straight track element →
left and right curve element ↓
In the first phase, definition of the elements are given.

18. Elements
In order to generate the models like the figure shows

19. Scheme of the method Off-line steps On-line steps Definition
Manual modeling
On-line steps
Parameter calculation
Assembling
In the second phase,

20. Parameter calculation
Parameters are calculated according to the equations

21. Assembling Transformations in OpenGL translate rotate scale
In order to assemble the elements dynamically during the simulation.

22. Experimental Result
Here are some results based on our method.

23. Demo
We also provide a demo to show a visual simulation system which adopts the method.

24. Outlines 1. Introduction 2. Challenges & Related Works
3. Our method & Results
4. Conclusion & Future Works

25. Advantages Save memory Efficient and easy to carry out
repeatedly use of track element models
against → load more than terabytes of data
Efficient and easy to carry out
element models are accomplished (stored in binary files) before the program is running
against → modeling during the time when the program is running
In summery, a hierarchical and dynamic framework for modeling large-scale railway-
track described with its CL is introduced
The framework has many benefits. For example,
this bottom-up strategy, which bases on element models, saves memory a lot
It provides a new way of simplification in track modeling.
In additional, the method is also very efficient and easy to realize,
is competent for real-time rendering and user interactions.

26. Future works This work assumes that the height of track is a constant.
Thus, modeling track with slope will be one of our future works.
This work assumes that the height of track is a constant, because the variation of height would sharply
increase the complexity of element models. Deformations for element models may be a feasible direction
to solve this problem. Thus, modeling track with slope will be one of our future works.

27. Thanks for your attention ！
Q and A
Thanks for your attention ！