# Burning Down an Entire Virtual Forest! 🌲🔥 ## Метаданные - **Канал:** Two Minute Papers - **YouTube:** https://www.youtube.com/watch?v=AGCH1GR7pPU - **Дата:** 22.06.2021 - **Длительность:** 5:39 - **Просмотры:** 117,081 - **Источник:** https://ekstraktznaniy.ru/video/13885 ## Описание ❤️ Check out the Gradient Dissent podcast by Weights & Biases: http://wandb.me/gd  📝 The paper "Fire in Paradise: Mesoscale Simulation of Wildfires" is available here: http://computationalsciences.org/publications/haedrich-2021-wildfires.html 🙏 We would like to thank our generous Patreon supporters who make Two Minute Papers possible: Aleksandr Mashrabov, Alex Haro, Andrew Melnychuk, Angelos Evripiotis, Benji Rabhan, Bryan Learn, Christian Ahlin, Eric Haddad, Eric Martel, Gordon Child, Ivo Galic, Jace O'Brien, Javier Bustamante, John Le, Jonas, Kenneth Davis, Lorin Atzberger, Lukas Biewald, Matthew Allen Fisher, Mark Oates, Michael Albrecht, Nikhil Velpanur, Owen Campbell-Moore, Owen Skarpness, Ramsey Elbasheer, Steef, Taras Bobrovytsky, Thomas Krcmar, Torsten Reil, Tybie Fitzhugh, Ueli Gallizzi. If you wish to appear here or pick up other perks, click here: https://www.patreon.com/TwoMinutePapers Károly Zsolnai-Fehér's links: Instagram: https://www.instagram.com/twominutepapers/ Tw ## Транскрипт ### [] Dear Fellow Scholars, this is Two Minute Papers with Dr. Károly Zsolnai-Fehér. In a previous episode not so long ago, we burned down a virtual tree. This was possible through an amazing simulation paper from 4 years ago, where each leaf has its own individual mass and area, they burn individually, transfer heat to their surroundings, and finally, branches bend, and, look can eventually even break in this process. How quickly did this run? Of course, in real time. Well, that is quite a paper, so if this was so good, how does anyone improve that? Burn down another virtual tree? No, that would be too easy. You know what, instead, let’s set on fire an entire virtual forest. Oh yeah! Here you see a simulation of a devastating fire from a lightning strike in Yosemite national park. The simulations this time around are typically sped up a great deal to be able to give us a better view of how it spreads, so if you see some flickering, that is the reason for that. But wait, is that really that much harder? Why not just put a bunch of trees next to each other and start the simulation? Would that work? The answer is a resounding no. Let’s have a look why, and with that, hold on to your papers because here comes the best part: it also simulates not only the fire, but cloud dynamics as well. Here you see how the wildfire creates lots of hot, and dark smoke closer to the ground, and, wait for it…yes! There we go! Higher up, the condensation of water creates this lighter, cloudy region. Yes, this is key to the simulation, not just because of the aesthetic effects, but this wildfire can indeed create a cloud type that goes by the name flammagenitus. So, is that good or bad news? Well, both! Let’s start with the good news: it often produces rainfall, which helps putting out the fire. Well, that is wonderful news, so then, what is so bad about it? Well, flammagenitus clouds may also trigger a thunderstorm, and thus, create another huge fire. That’s bad news number one. And bad news number two: it also occludes the fire, thereby making it harder to locate and extinguish it. So, got it, add cloud dynamics to the tree fire simulator, and we are done, right? No, not even close. In a forest fire simulation, not just clouds, everything matters. For instance, first we need to take into consideration the wind intensity and direction. ### Wind speed [2:57] This can mean the difference between a manageable or a devastating forest fire. Second, it takes into consideration the density and moisture intensity of different tree types ### Density and moisture intensity [3:10] - for instance, you see that the darker trees here are burning down really slowly. Why is that? This is because these trees are denser birches and oak trees. Third, the distribution of the trees also matter. Of course, the more the area is covered by trees, the more degrees of freedom there are for the fire to spread. And, fourth. Fire can not only spread horizontally from tree to tree, but vertically too. ### Vertical spread [3:45] Look! When a small tree catches fire, this can happen. So, as we established from the previous paper, one tree catching fire can be simulated in real time. What about an entire forest? Let’s take the simulation with the most number of trees, my goodness, they simulated 120k trees there. And the computation time for one simulation step was…95. So, 95 what? 95 milliseconds. Wow! So this thing runs interactively, which means that all of these phenomena can be simulated in close to real time. With that, we can now model how a fire would spread in real forests around the world, test different kinds of fire barriers and their advantages, and we can even simulate how to effectively put out the fire. And don’t forget, we went from simulating one burning tree to a hundred and twenty thousand in just one more paper down the line. What a time to ### Gradient Dissent [5:06] be alive! Thanks for watching and for your generous support, and I'll see you next time!