1 99:59:59,999 --> 99:59:59,999 Okay, in our last little vignette into the 2 99:59:59,999 --> 99:59:59,999 history of agent-bnased modelling, we're 3 99:59:59,999 --> 99:59:59,999 going to talk about particle systems 4 99:59:59,999 --> 99:59:59,999 and computer graphics. So, early on 5 99:59:59,999 --> 99:59:59,999 in computer graphics, visualisations were essentially 6 99:59:59,999 --> 99:59:59,999 accompalished by creating large, flat surfaces 7 99:59:59,999 --> 99:59:59,999 and then combining in ways to create what was 8 99:59:59,999 --> 99:59:59,999 computer grpahics. And to tis day, a lot of 9 99:59:59,999 --> 99:59:59,999 computer grpahics is still done that way. 10 99:59:59,999 --> 99:59:59,999 Like you place textures on these polygons and you place them 11 99:59:59,999 --> 99:59:59,999 But there's another way to do graphics, which is 12 99:59:59,999 --> 99:59:59,999 to think of graphics, not as a polygon 13 99:59:59,999 --> 99:59:59,999 but just as a point, and you give that point a size. 14 99:59:59,999 --> 99:59:59,999 But your'e essentially mani;ulating the centre of that 15 99:59:59,999 --> 99:59:59,999 point rather than manipulating all four corners 16 99:59:59,999 --> 99:59:59,999 of a square.... 17 99:59:59,999 --> 99:59:59,999 and in fact, surfaces don't work very well for smoke, stars 18 99:59:59,999 --> 99:59:59,999 light or even birds, for that matter. So, instead you need 19 99:59:59,999 --> 99:59:59,999 some soft of point representation 20 99:59:59,999 --> 99:59:59,999 as we talked about. And this point 21 99:59:59,999 --> 99:59:59,999 representation of graphics came to 22 99:59:59,999 --> 99:59:59,999 be known as particle systems. And what's 23 99:59:59,999 --> 99:59:59,999 interesting is that once that you think 24 99:59:59,999 --> 99:59:59,999 of these things as points, well a lot of our physics models 25 99:59:59,999 --> 99:59:59,999 are actually written as points, as idealised points 26 99:59:59,999 --> 99:59:59,999 so then you can apply those physics models to computer 27 99:59:59,999 --> 99:59:59,999 graphics in a very easy and intuitive 28 99:59:59,999 --> 99:59:59,999 way and you can create interesting displays. 29 99:59:59,999 --> 99:59:59,999 in computer graphics. So, how does this 30 99:59:59,999 --> 99:59:59,999 relate to ABM? Well, particle systems 31 99:59:59,999 --> 99:59:59,999 also exhibit emergent phenomenon. So, for example, if I'm 32 99:59:59,999 --> 99:59:59,999 representing a bunch of 33 99:59:59,999 --> 99:59:59,999 red particles as a fire, then when they overlap, 34 99:59:59,999 --> 99:59:59,999 depending on how I've done the transparecies, they 35 99:59:59,999 --> 99:59:59,999 appear denser of lighter so I can get 36 99:59:59,999 --> 99:59:59,999 this like flickering flame like effect htat looks 37 99:59:59,999 --> 99:59:59,999 very similar to a fire, right.