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## STBurn -- Burn Simulation

### STBurn

Having read the information on the previous page, you will figure out quickly how to use it. There is balloon/tool tip help for most tunable parameters.

STBurn will do complete burn simulations as fast as it can. I really put some effort into making the algorithm fast (and it actually outperforms quite a lot the an older burn version of some other former student...). To see how fast it is, the sps= value in the right top displays the complete burn simulations per second.

The program works as follows: It repeatedly does a complete burn sim meaning: it creates a new forest with some tree density, automatically ignites it (as set in the Ignition box), runs the sim's time ticks until no tree is burning any more. Now, the program knows: the fraction of burnt trees and the duration of the fire (in time ticks).
This data is collected as follows:
STBurn holds a number of records (see Record limit spin box) which save the collected data. Newer data will replace older data and all the data in the record is presented in the statistics diagram. Hence, by using a small value for the limit (2000 or so) you can watch the curves deform while you change parameters such as the tree mass, the initial fire size or the combustibility, etc. The current number of records is displayed after n= on the right top.

If the statistics window has the input focus, you can switch on the different components using the keys e,c and d as indicated at the bottom of the window. The X-axis displays the tree density, the Y-axis is primarily the fraction of burned trees. Each simulation is given a blue pixel (matching tree density and burned fratction). The blue points are averaged together for every 0.01% tree density and displayed using the red curve. The amber vertical bars visualize the standard deviation of the fraction of burnt trees.
The green curve, finally, displays the duration of the fire as function of the tree density. The duration-Y-axis is scaled in a way that the longest duration fills the whole diagram.

It may seem unexpected that the diagram goes up in the left bottom corner but the reason is simple: It's the (auto-) ignition. If you have a tree density of, say, 0.005 and ignite 5 of the trees then this may already be 20% of all trees. The fire will not spread but as we initially set fire on 20% of the trees, the fraction will stay 20% at the end of the sim and be displayed.

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