Difference between revisions of "Forest Fire Tutorial"
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− | <td height="150">If I am a healthy tree and I am next to a burning tree, with a | + | <td height="150">If I am a healthy tree and I am next to a burning tree, with a certain percent chance, I will change into a burning tree myself. This probability be a number (e.g. 80%) or can also be defined by a simulation property called Fire_Spreading_Probability.</td> |
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− | <td height="100">If I am a burning tree, with | + | <td height="100">If I am a burning tree, with certain percent chance i will turn into a completely burnt tree, to simulate the fire dying out. This probability can be a constant (e.g. 50%) or can be a "Fire_Die_Out_Probability" simulation property for easier experimentation. </td> |
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− | <td align="top" height="200">The PERCEIVE method of the tree determines whether a healthy tree should start burning - it does so if the healthy tree is next to at least one burning tree, with a certain probability | + | <td align="top" height="200">The PERCEIVE method of the tree determines whether a healthy tree should start burning - it does so if the healthy tree is next to at least one burning tree, with a certain probability (defined by the simulation property Fire_Spreading_Probability in this case). Please note that the PERCEIVE method does not actually set the tree on fire by turning it into a burning tree, but sets a variable/flag to indicate that the tree should be burning. This way, all the trees get a chance to determine whether they should be burning in parallel, avoiding the issue encountered in the previous section. |
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− | <td align="top" height="250">The ACT method of the tree actually carries out the burning: if the tree is healthy and its "burning" flag is set, it turns into the burning tree. Otherwise, if it's an already burning tree, with a certain probability, it turns into a burnt tree and increments the @burnt_trees counter (simulation property) | + | <td align="top" height="250">The ACT method of the tree actually carries out the burning: if the tree is healthy and its "burning" flag is set, it turns into the burning tree. Otherwise, if it's an already burning tree, with a certain probability (defined by the simulation property Fire_Die_Out_Probability), it turns into a burnt tree and increments the @burnt_trees counter (simulation property). |
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Revision as of 23:00, 21 August 2011
Contents
- 1 Introduction
- 2 Creating the Project
- 3 Creating Agents
- 4 Creating a Forest
- 5 Programing the Tree
- 6 Programming the Controller to synchronize/parallelize tree burning
- 7 Regenerating the forest with a certain density
- 8 Simulation Properties
- 9 Updating the world to include Controller and Start_Here agents
Introduction
The forest fire simulation built with this tutorial enables you to explore how forest fires unravel by letting you set fires to virtual forests with different tree densities. This simulation can them be used for data collection and analysis in math units.
Creating the Project
Launch AgentCubes and create a new project (choose the location and name of your project).
Creating Agents
The simulation has a Tree agent, a Ground agent, a Controller agent, and a Start Here agent.
Creating a Forest
If you haven't created a new world, use the + button at the top of the project window to create one. Please note that later on we will be generating the forest automatically, but for now let's do this manually: Select your Ground agent in the Agents list and using the Volume Insert tool, lay out a layer of Ground agents in the background of your world. Then select your healthy Tree agent shape and using the Draw tool place a few on the Ground. Place one Tree_Burning, which will start the fire, somewhere in the middle of the world to create a forest like the one shown below.
This is a good time to save the world!
Programing the Tree
We need to program the Tree agent to catch on fire if it's next to a burning tree and burn completely when the fire dies out. Select the Tree agent in the Agents list and its behavior will appear in the Behavior view. Create two rules for the tree:, one to start the fire if it's a healthy tree with a certain probability, and one to stop it when the fire dies out with a certain probability:
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Now try out your simulation by running it. Depending on the density of the forest you created, the fire spreads widely or dies out quickly.
But notice something: if you reset your world to its original saved state and hit the Step button to run one cycle of the simulation you will get something like this:
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How can we fix this? We need to coordinate the behavior of the tree so that within the same simulation cycle, all the trees have a chance to determine if they should be burning first, and then actually perform the burning actions. For that, we can use a Controller agent to synchronize the tree behavior (make it parallel).
Programming the Controller to synchronize/parallelize tree burning
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Now try running your simulation again. Stepping through your fire simulation should look like this:
<youtube>bbAA5qWKX50</youtube>
Regenerating the forest with a certain density
File:Controller behavior.png |
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Simulation Properties
Running your simulation will create the simulation properties used without your explicitly creating them. But especially for the input properties (e.g. Desired_Density), it's good to create them yourself so you can initialize it to the values you want - otherwise, the simulation automatically creates them with 0 as the default value. Pull up the Simulation Properties editor, using Tools->Simulation Properties and add the following properties:
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Once you have your properties set, make sure you hit the Save button to save them.
Please note that we capitalized the DESIRED_DENSITY and the PERCENT_BURNT to make it easier for users to tell which simulations properties they need to manipulate or look at for their experimentation.
Updating the world to include Controller and Start_Here agents
Add a controller agent and a Start_Here agent to your world as shown below, save your world, and you are ready to start data collection for the Sampling and Bivariate Data Analysis unit.