1 00:00:08,960 --> 00:00:11,919 Hello, and welcome to the Physics World weekly 2 00:00:11,919 --> 00:00:12,419 podcast, 3 00:00:12,884 --> 00:00:15,945 the last episode of 2025. 4 00:00:16,484 --> 00:00:18,664 And it features Pat Hanrahan, 5 00:00:19,125 --> 00:00:19,945 who studied 6 00:00:20,245 --> 00:00:22,585 nuclear engineering and biophysics 7 00:00:23,285 --> 00:00:25,704 before becoming a founding employee 8 00:00:26,164 --> 00:00:26,984 of Pixar 9 00:00:27,449 --> 00:00:28,669 Animation Studios 10 00:00:29,210 --> 00:00:30,589 in the nineteen eighties. 11 00:00:31,289 --> 00:00:34,429 That conversation is coming up after this message 12 00:00:34,489 --> 00:00:35,469 about a webinar 13 00:00:35,850 --> 00:00:36,909 that we're presenting 14 00:00:37,289 --> 00:00:39,229 with Leo Cancer Care. 15 00:00:39,905 --> 00:00:41,364 It's called unlocking 16 00:00:41,905 --> 00:00:45,284 novel radiation beams for cancer treatment 17 00:00:45,664 --> 00:00:47,844 with upright patient positioning, 18 00:00:48,384 --> 00:00:51,045 and it will feature a panel of leading 19 00:00:51,104 --> 00:00:51,604 clinicians 20 00:00:51,984 --> 00:00:52,804 and experts. 21 00:00:53,789 --> 00:00:56,770 They will discuss how the shift in patient 22 00:00:56,909 --> 00:00:57,409 positioning 23 00:00:57,869 --> 00:00:59,570 is enabling the exploration 24 00:01:00,109 --> 00:01:02,049 of new treatment geometries 25 00:01:02,829 --> 00:01:03,570 and supporting 26 00:01:03,949 --> 00:01:04,689 the development 27 00:01:05,150 --> 00:01:05,969 of advanced 28 00:01:06,564 --> 00:01:08,344 future cancer therapies. 29 00:01:09,284 --> 00:01:12,424 The live event is aimed at medical physicists, 30 00:01:13,284 --> 00:01:14,584 radiation oncologists, 31 00:01:15,685 --> 00:01:16,185 radiotherapy 32 00:01:16,805 --> 00:01:17,305 planners, 33 00:01:17,685 --> 00:01:18,584 and researchers 34 00:01:18,965 --> 00:01:19,864 in the field. 35 00:01:20,700 --> 00:01:24,780 Participants will learn about this paradigm shift in 36 00:01:24,780 --> 00:01:25,280 radiation 37 00:01:25,579 --> 00:01:26,079 therapy, 38 00:01:26,939 --> 00:01:28,239 gain an understanding 39 00:01:28,619 --> 00:01:30,560 of emerging and novel 40 00:01:31,019 --> 00:01:31,519 radiation 41 00:01:31,819 --> 00:01:33,040 beam modalities, 42 00:01:33,944 --> 00:01:34,765 and discover 43 00:01:35,064 --> 00:01:36,045 how foundational 44 00:01:36,825 --> 00:01:37,325 radiation 45 00:01:37,704 --> 00:01:38,204 physics 46 00:01:38,825 --> 00:01:39,325 translates 47 00:01:39,784 --> 00:01:41,805 into real world impact 48 00:01:42,105 --> 00:01:43,484 in cancer care. 49 00:01:44,265 --> 00:01:47,179 The webinar is on the February 17 50 00:01:47,640 --> 00:01:48,780 at 4PM 51 00:01:49,239 --> 00:01:49,739 GMT. 52 00:01:50,520 --> 00:01:52,380 That's 11AM 53 00:01:52,680 --> 00:01:54,299 Eastern Standard Time. 54 00:01:54,920 --> 00:01:57,420 You can register for this free event 55 00:01:57,719 --> 00:01:59,579 on the Physics World website. 56 00:02:02,165 --> 00:02:05,765 Earlier this year, Physics World's Margaret Harris attended 57 00:02:05,765 --> 00:02:06,584 the Heidelberg 58 00:02:07,045 --> 00:02:07,545 Laureate 59 00:02:07,844 --> 00:02:09,305 Forum in Germany. 60 00:02:10,004 --> 00:02:14,104 This international event brings together early career researchers 61 00:02:14,689 --> 00:02:17,349 with some winners of the most prestigious 62 00:02:17,650 --> 00:02:19,189 awards in mathematics 63 00:02:19,569 --> 00:02:21,030 and computer science. 64 00:02:21,650 --> 00:02:24,610 There, she spoke to a laureate who's also 65 00:02:24,610 --> 00:02:28,389 won three academy awards. Here's that conversation. 66 00:02:36,794 --> 00:02:39,114 So I'm talking to Pat Hanrahan, who won 67 00:02:39,114 --> 00:02:41,995 the Association for Computing Machineries AM Turing Award 68 00:02:41,995 --> 00:02:42,974 in 2019 69 00:02:43,310 --> 00:02:45,870 for contributions to three d computer graphics or 70 00:02:45,870 --> 00:02:46,370 CGI. 71 00:02:47,069 --> 00:02:48,509 So you're best known for that type of 72 00:02:48,509 --> 00:02:50,269 work, but you actually started out, I think, 73 00:02:50,269 --> 00:02:52,989 in nuclear engineering Yes. And then you got 74 00:02:52,989 --> 00:02:55,229 a PhD in biophysics. Yes. So how did 75 00:02:55,229 --> 00:02:56,935 you get into those subjects? Tell me about 76 00:02:56,935 --> 00:02:58,935 nuclear engineering first. Well, when I was in 77 00:02:58,935 --> 00:03:00,615 school, I I really felt I wanted to 78 00:03:00,615 --> 00:03:03,094 become a physicist. Anyway, I like math too, 79 00:03:03,094 --> 00:03:04,935 and I like science in general, but I 80 00:03:04,935 --> 00:03:07,415 think physics was the field that was most 81 00:03:07,415 --> 00:03:09,270 interesting to me. And so, yeah, when I 82 00:03:09,270 --> 00:03:11,030 went to the University of Wisconsin actually, it 83 00:03:11,030 --> 00:03:12,790 was it was it was doubly nice because 84 00:03:12,790 --> 00:03:14,469 they had this really nice, what they call, 85 00:03:14,469 --> 00:03:15,370 honors program, 86 00:03:15,750 --> 00:03:17,270 where you have a lot of freedom in 87 00:03:17,270 --> 00:03:19,270 what classes you took and all that. So, 88 00:03:19,270 --> 00:03:21,349 you know, not just take physics, but do 89 00:03:21,349 --> 00:03:24,064 other things as well. Take chemistry, biology, other 90 00:03:24,064 --> 00:03:24,564 sciences. 91 00:03:24,864 --> 00:03:26,625 So yeah. So I was always interested in 92 00:03:26,625 --> 00:03:28,704 physic. I love my intro physics course. I 93 00:03:28,704 --> 00:03:29,364 can still 94 00:03:29,664 --> 00:03:32,144 remember the lectures and, you know, going through 95 00:03:32,144 --> 00:03:33,044 it all. And, 96 00:03:33,344 --> 00:03:35,104 yeah. So I just loved physics, you know, 97 00:03:35,104 --> 00:03:36,884 all the way through the undergraduate 98 00:03:37,185 --> 00:03:38,084 physics, mechanics, 99 00:03:38,730 --> 00:03:39,230 electrodynamics, 100 00:03:40,169 --> 00:03:42,569 quantum mechanics. I just loved all those courses, 101 00:03:42,569 --> 00:03:43,550 my favorite courses. 102 00:03:43,849 --> 00:03:46,169 But why nuclear engineering specifically? Why not? Well, 103 00:03:46,169 --> 00:03:47,610 I think it was mostly because of this 104 00:03:47,610 --> 00:03:50,090 honors program. I was actually I actually and 105 00:03:50,090 --> 00:03:51,770 I when I went there, the chairman of 106 00:03:51,770 --> 00:03:52,349 the department, 107 00:03:52,650 --> 00:03:53,790 offered me a job, 108 00:03:54,665 --> 00:03:56,344 and he was the chair of the nuclear 109 00:03:56,344 --> 00:03:58,745 regulatory commission at the time. So I ended 110 00:03:58,745 --> 00:04:00,665 up, you know, in in this department. But, 111 00:04:00,665 --> 00:04:02,025 you know, I was he was working for 112 00:04:02,025 --> 00:04:03,784 the nuclear regulatory commission. This was, you know, 113 00:04:03,784 --> 00:04:05,165 like, in the late seventies. 114 00:04:05,705 --> 00:04:08,025 You know, nuclear power was having you know, 115 00:04:08,025 --> 00:04:10,120 people were pretty down on that. Right? And 116 00:04:10,120 --> 00:04:11,400 when I was reading about all this stuff, 117 00:04:11,400 --> 00:04:12,919 I got pretty down on it too because 118 00:04:12,919 --> 00:04:14,680 they weren't really addressing a lot of the 119 00:04:14,680 --> 00:04:16,439 currents. I think that's maybe changing a little 120 00:04:16,439 --> 00:04:17,740 bit, but I was definitely 121 00:04:18,279 --> 00:04:20,620 not that interested especially at towards the end. 122 00:04:21,160 --> 00:04:23,560 So I wanted to work on other areas 123 00:04:23,560 --> 00:04:24,220 of physics. 124 00:04:24,654 --> 00:04:26,415 I did a lot of theoretical physics. You 125 00:04:26,415 --> 00:04:28,095 know? Like, when I was a graduate student, 126 00:04:28,095 --> 00:04:29,935 I I had to take, like, I don't 127 00:04:29,935 --> 00:04:32,415 know, five courses in quantum mechanics, you know, 128 00:04:32,415 --> 00:04:34,574 quantum field theory. You know? I was really 129 00:04:34,574 --> 00:04:37,079 headed towards the theoretical physics thing, but I 130 00:04:37,079 --> 00:04:38,519 don't know what you I I the the 131 00:04:38,519 --> 00:04:41,000 low level of physics just wasn't really exciting 132 00:04:41,000 --> 00:04:42,439 me. So I I wanted to be a 133 00:04:42,439 --> 00:04:43,899 physicist, but I 134 00:04:44,360 --> 00:04:46,279 wanted to work on sort of higher level 135 00:04:46,279 --> 00:04:46,779 problems. 136 00:04:47,560 --> 00:04:50,439 So I I admired, like, Francis Crick, and 137 00:04:50,439 --> 00:04:51,660 he was, like, a theoretical 138 00:04:52,524 --> 00:04:53,904 biologist in some sense. 139 00:04:54,285 --> 00:04:55,725 And I thought, well, maybe I could become, 140 00:04:55,725 --> 00:04:57,264 like, a theoretical biologist. 141 00:04:57,964 --> 00:04:59,584 And then I met this person, 142 00:05:00,045 --> 00:05:01,964 and I was, he had was one of 143 00:05:01,964 --> 00:05:04,865 the founders of the computational neuroscience program. 144 00:05:05,319 --> 00:05:07,800 Or well, I'm sorry. Not computational neuroscience. That 145 00:05:07,800 --> 00:05:11,160 didn't exist. Neuroscience program. And, he was working 146 00:05:11,160 --> 00:05:13,319 on neurobiology of nematodes. He had worked for 147 00:05:13,319 --> 00:05:14,139 Sydney Brenner. 148 00:05:14,600 --> 00:05:16,279 And so I thought, well, I could I 149 00:05:16,279 --> 00:05:17,560 could do you know, he and they weren't 150 00:05:17,560 --> 00:05:19,319 being very quantitative, and I thought I could, 151 00:05:19,319 --> 00:05:21,555 like, apply what I know about physics to 152 00:05:21,555 --> 00:05:23,314 help them, you know, build up models of 153 00:05:23,314 --> 00:05:25,154 the nervous system. And I I started doing 154 00:05:25,154 --> 00:05:27,715 some simulations and things like that. Yeah. And 155 00:05:27,715 --> 00:05:28,995 is that about the time that you got 156 00:05:28,995 --> 00:05:31,314 first involved in Pixar, the project that became 157 00:05:31,314 --> 00:05:33,395 the first Toy Story film? No. That took 158 00:05:33,395 --> 00:05:34,675 a little while. I mean, you know, you 159 00:05:34,675 --> 00:05:37,170 have to realize computer graphics didn't exist then. 160 00:05:37,170 --> 00:05:39,410 It really didn't exist. I mean, you know, 161 00:05:39,410 --> 00:05:41,649 it just did not exist. My advice so 162 00:05:41,649 --> 00:05:43,170 it turned out it's sort of funny story. 163 00:05:43,170 --> 00:05:46,069 Sydney Brenner, you know, Nobel laureate in biology. 164 00:05:46,610 --> 00:05:48,129 There was he had two a bunch of 165 00:05:48,129 --> 00:05:51,165 colleagues and students, Francis Crick. There was another 166 00:05:51,165 --> 00:05:53,245 guy named John White and another guy named 167 00:05:53,245 --> 00:05:54,064 John Sulston. 168 00:05:54,444 --> 00:05:56,145 And John White is famous for 169 00:05:56,524 --> 00:05:57,024 determining, 170 00:05:57,645 --> 00:05:59,725 the structure of the nervous system of c 171 00:05:59,725 --> 00:06:01,245 l. So they all worked on C. Elegans, 172 00:06:01,245 --> 00:06:03,185 which is a a free living nematode. 173 00:06:03,680 --> 00:06:06,240 So, John White had, like, figured out the 174 00:06:06,240 --> 00:06:08,879 entire wiring grant by sectioning the words and 175 00:06:08,879 --> 00:06:11,360 worm and tracing all the neurons. And, 176 00:06:11,839 --> 00:06:14,019 John Solston had, worked on 177 00:06:14,560 --> 00:06:17,680 developmental biology, and he recorded, you know, how 178 00:06:17,680 --> 00:06:18,339 the cells 179 00:06:18,814 --> 00:06:20,574 divided, you know, from an egg all the 180 00:06:20,574 --> 00:06:22,435 way to a full grown one. 181 00:06:22,975 --> 00:06:24,975 And, anyways, the three of them all got 182 00:06:24,975 --> 00:06:25,954 really the same computers. 183 00:06:27,294 --> 00:06:27,794 And, 184 00:06:28,334 --> 00:06:30,495 and so, you know, my my adviser was 185 00:06:30,495 --> 00:06:32,014 in that group, and he was trying to 186 00:06:32,014 --> 00:06:33,555 convince me to work on computers. 187 00:06:34,129 --> 00:06:36,370 And I didn't have any background in computers. 188 00:06:36,370 --> 00:06:37,829 So I started simulating, 189 00:06:38,370 --> 00:06:39,589 this nervous system, 190 00:06:40,129 --> 00:06:42,209 and I had you, write these programs that 191 00:06:42,209 --> 00:06:43,829 simulated. I was, like, solving, 192 00:06:44,209 --> 00:06:47,169 like, basically cable equations for neurons because these 193 00:06:47,169 --> 00:06:49,189 neurons are, like, you know, electrical cables. 194 00:06:49,995 --> 00:06:52,074 But I needed to do visualization. I had 195 00:06:52,074 --> 00:06:53,435 to be able to see my result. Like, 196 00:06:53,435 --> 00:06:55,915 you just so my roommate introduced me to 197 00:06:55,915 --> 00:06:57,275 computer graphics. He said, oh, by the way, 198 00:06:57,275 --> 00:06:58,975 do you know about this graphic stuff? 199 00:06:59,355 --> 00:07:00,975 You know, I just sort of got enchanted 200 00:07:01,115 --> 00:07:02,235 by what I could do with it because 201 00:07:02,235 --> 00:07:03,835 I could take all my theories, like, whether 202 00:07:03,835 --> 00:07:06,580 it was simulation of neurons or whatever I 203 00:07:06,580 --> 00:07:08,819 was interested in and see it, you know, 204 00:07:08,819 --> 00:07:11,080 make it really concrete. And it just became 205 00:07:11,779 --> 00:07:13,460 even more fun. You know? Like, the the 206 00:07:13,460 --> 00:07:14,439 physics was suddenly 207 00:07:14,740 --> 00:07:16,500 infinitely more fun because I could see it. 208 00:07:16,500 --> 00:07:18,564 You know? Like, I could do animations, 209 00:07:18,944 --> 00:07:20,305 not much animation, but I could at least 210 00:07:20,305 --> 00:07:21,904 make pictures and so on. So I sort 211 00:07:21,904 --> 00:07:24,145 of got seduced by that idea, and it 212 00:07:24,145 --> 00:07:26,225 it was a wide open field. You know? 213 00:07:26,225 --> 00:07:28,305 Physics and, you know, biology was, you know, 214 00:07:28,305 --> 00:07:30,680 sort of slow paced. This was, like, completely 215 00:07:30,680 --> 00:07:32,759 wide open. So, like like like, the first 216 00:07:32,759 --> 00:07:34,280 week I worked on it, I, like, wrote 217 00:07:34,280 --> 00:07:36,280 a paper. I got accepted in the major 218 00:07:36,280 --> 00:07:37,800 conference. You know? Whereas in physics, you know, 219 00:07:37,800 --> 00:07:39,319 I'd been a grad student for a couple 220 00:07:39,319 --> 00:07:41,560 years, never written a paper. And so then 221 00:07:41,560 --> 00:07:43,080 I decided I had you go learn more 222 00:07:43,080 --> 00:07:44,220 about computer graphics, 223 00:07:44,794 --> 00:07:46,714 but, you know, because there was nobody there. 224 00:07:46,714 --> 00:07:48,954 There was only one or two places in 225 00:07:48,954 --> 00:07:50,794 the world that was doing computer graphics, and 226 00:07:50,794 --> 00:07:53,435 eventually, I ended up at Pixar a couple 227 00:07:53,435 --> 00:07:54,495 years later. Yeah. 228 00:07:55,435 --> 00:07:58,314 And a lot of your research on computer 229 00:07:58,314 --> 00:08:01,720 generated imagery focuses on getting the simulated world 230 00:08:01,720 --> 00:08:02,459 to display 231 00:08:03,079 --> 00:08:05,000 things in the way it's grounded in physics. 232 00:08:05,000 --> 00:08:06,519 Yeah. Yeah. You know, you literally wrote the 233 00:08:06,519 --> 00:08:09,479 book about physically based rendering. Yeah. What are 234 00:08:09,479 --> 00:08:11,639 the benefits of that approach, and what are 235 00:08:11,639 --> 00:08:14,055 some of the main challenges in it? That's 236 00:08:14,055 --> 00:08:15,035 a great question. 237 00:08:15,335 --> 00:08:17,095 You know, I love that question. I mean, 238 00:08:17,095 --> 00:08:18,694 you know, you know, we're we're creating a 239 00:08:18,694 --> 00:08:21,335 virtual world, and the world, you know, has 240 00:08:21,335 --> 00:08:23,495 physics in it. I mean, you know, and 241 00:08:23,495 --> 00:08:25,175 just imagine. I mean, what we did, we're 242 00:08:25,175 --> 00:08:26,694 just trying to create a world that, like, 243 00:08:26,694 --> 00:08:29,120 if somebody looked at it had all the 244 00:08:29,120 --> 00:08:31,439 phenomena that we think of in physics and 245 00:08:31,439 --> 00:08:33,759 even biology as well, but all these phenomena. 246 00:08:33,759 --> 00:08:35,160 So, you know, like, what are some of 247 00:08:35,160 --> 00:08:37,299 the found well, a cloud might move. Right? 248 00:08:37,759 --> 00:08:40,019 Wind will move the leaves of the tree. 249 00:08:40,079 --> 00:08:41,519 You know, you could have an object, a 250 00:08:41,519 --> 00:08:42,339 rock falling. 251 00:08:42,725 --> 00:08:44,725 You know, get out something a building kind 252 00:08:44,725 --> 00:08:47,045 of blowing apart. You could have, you know, 253 00:08:47,045 --> 00:08:50,485 cloth, you know, conforming to somebody's skin. You 254 00:08:50,485 --> 00:08:52,965 have the muscles moving the body. I mean, 255 00:08:52,965 --> 00:08:54,965 there's just physics everywhere in the world. Right? 256 00:08:54,965 --> 00:08:56,570 And so, you know, if we're trying to 257 00:08:56,570 --> 00:08:57,970 simulate all I mean, we're trying to make 258 00:08:57,970 --> 00:08:59,690 a picture of all this stuff. I mean, 259 00:08:59,690 --> 00:09:01,050 how else would you do it? I mean, 260 00:09:01,050 --> 00:09:02,889 you you have to in some sense, you 261 00:09:02,889 --> 00:09:04,889 have to somehow capture the physics of the 262 00:09:04,889 --> 00:09:06,490 everyday world. It's I I call it the 263 00:09:06,490 --> 00:09:08,970 everyday world because it's at the human scale. 264 00:09:08,970 --> 00:09:11,115 You know? It's what we see around us. 265 00:09:11,355 --> 00:09:13,534 And I mostly worked on, 266 00:09:13,914 --> 00:09:16,075 simulating the appearance of it, right, which is 267 00:09:16,075 --> 00:09:17,595 like, you know, you know, why does it 268 00:09:17,595 --> 00:09:19,274 look the way it does? Like, why how 269 00:09:19,274 --> 00:09:22,315 do, like, materials scatter light, and how does 270 00:09:22,315 --> 00:09:25,259 light get transported through the environment, and, you 271 00:09:25,259 --> 00:09:27,899 know, even how cameras simulate cameras and simulate 272 00:09:27,899 --> 00:09:29,820 light sources. So, yeah, so if you look 273 00:09:29,820 --> 00:09:31,420 at the what we actually ended up doing, 274 00:09:31,420 --> 00:09:33,179 if you look at that book, you know, 275 00:09:33,179 --> 00:09:34,080 we write down 276 00:09:34,460 --> 00:09:36,700 a bunch of equations that describe the scattering 277 00:09:36,700 --> 00:09:39,279 of light off surfaces and off infinite media, 278 00:09:39,465 --> 00:09:41,245 and then we just solve this 279 00:09:42,024 --> 00:09:44,264 solve for the lightning distribution in the world. 280 00:09:44,264 --> 00:09:46,345 You know? And it's a just a giant 281 00:09:46,345 --> 00:09:47,725 computational science problem. 282 00:09:48,105 --> 00:09:49,945 But the challenge is you have all these 283 00:09:49,945 --> 00:09:50,925 real world materials, 284 00:09:52,345 --> 00:09:53,884 which are both complex. 285 00:09:54,529 --> 00:09:57,009 You know, they're not just like ideal mirrors 286 00:09:57,009 --> 00:09:58,929 and, you know, one type of cars where 287 00:09:58,929 --> 00:10:00,690 I just, like, opened up an optics book 288 00:10:00,690 --> 00:10:02,290 and said, how much is in this book 289 00:10:02,290 --> 00:10:04,389 that would help us do this? Almost nothing. 290 00:10:04,690 --> 00:10:06,210 You know what I mean? Because, you know, 291 00:10:06,210 --> 00:10:07,889 how does light scatter off skin? How does 292 00:10:07,889 --> 00:10:10,085 light scatter off a rock? How does light 293 00:10:10,085 --> 00:10:12,565 scatter off a cloud? Just not detailed stuff 294 00:10:12,565 --> 00:10:14,644 in there. So we'd often have to come 295 00:10:14,644 --> 00:10:15,625 up with, you know, 296 00:10:16,004 --> 00:10:16,504 approximations 297 00:10:16,884 --> 00:10:17,784 and models 298 00:10:18,164 --> 00:10:20,325 for all these things. And I worked a 299 00:10:20,325 --> 00:10:22,164 lot. Like, I I worked on my papers 300 00:10:22,164 --> 00:10:23,464 as I'm modeling skin. 301 00:10:24,419 --> 00:10:26,339 Hair. How does light scatter from hair? How 302 00:10:26,339 --> 00:10:28,899 does light scatter from cloth? Stuff like that. 303 00:10:28,899 --> 00:10:30,339 But, anyways, when it all is said and 304 00:10:30,339 --> 00:10:31,940 done, you get, you know, like, a billion 305 00:10:31,940 --> 00:10:32,440 objects 306 00:10:32,820 --> 00:10:34,679 each with really complex materials, 307 00:10:35,059 --> 00:10:37,375 and then you have to solve for the 308 00:10:37,375 --> 00:10:38,115 lighting distribution, 309 00:10:38,574 --> 00:10:41,454 which is really complicated because the objects have 310 00:10:41,454 --> 00:10:44,274 complicated shape. So we use Monte Carlo techniques. 311 00:10:44,495 --> 00:10:46,174 You know? In fact, just like what they 312 00:10:46,174 --> 00:10:48,815 did up during the war to simulate the 313 00:10:48,815 --> 00:10:49,794 neutron transport, 314 00:10:50,110 --> 00:10:51,870 And that's actually was the connection back to 315 00:10:51,870 --> 00:10:54,509 my work in nuclear engineering. I had learned 316 00:10:54,509 --> 00:10:57,230 about transport theory and Monte Carlo techniques, you 317 00:10:57,230 --> 00:10:59,309 know, in school. And so, you know, I 318 00:10:59,309 --> 00:11:01,009 I sort of also just sort of gravitated 319 00:11:01,070 --> 00:11:02,590 towards those problems because those are the ones 320 00:11:02,590 --> 00:11:03,570 I knew to sell. 321 00:11:03,904 --> 00:11:06,144 So you actually won, one of your three 322 00:11:06,144 --> 00:11:08,544 Academy Awards, Oscars, in other words Yeah. Is 323 00:11:08,544 --> 00:11:11,585 specifically for developing that software that simulates the 324 00:11:11,585 --> 00:11:13,665 subsurface scattering of light Yes. Yeah. In in 325 00:11:13,665 --> 00:11:16,304 materials that are translucent. Yeah. Yeah. Why is 326 00:11:16,304 --> 00:11:18,144 that so difficult, and why is it so 327 00:11:18,144 --> 00:11:18,644 important 328 00:11:19,340 --> 00:11:21,980 for film and computer graphics? Yeah. Well, okay. 329 00:11:21,980 --> 00:11:23,980 Why is it important? Well, I'm looking at 330 00:11:23,980 --> 00:11:26,080 you, and your skin looks really healthy. 331 00:11:27,019 --> 00:11:28,300 I mean, you know, I mean, you know, 332 00:11:28,300 --> 00:11:30,940 in real people, skin is really important. Right? 333 00:11:30,940 --> 00:11:33,340 It has to look right. And until then, 334 00:11:33,340 --> 00:11:34,399 it looked like plastic. 335 00:11:34,715 --> 00:11:36,154 You know, it looked like, yeah, just were 336 00:11:36,154 --> 00:11:38,235 completely covered in makeup. You know? You know, 337 00:11:38,235 --> 00:11:40,554 makeup and things like that, you know, almost 338 00:11:40,554 --> 00:11:41,915 like pink. You know what I mean? They're 339 00:11:41,915 --> 00:11:43,915 just very matte and, you know, very I 340 00:11:43,915 --> 00:11:45,995 mean, you know, that's why they're matte. They're 341 00:11:45,995 --> 00:11:47,740 not they did not you know, don't have 342 00:11:47,740 --> 00:11:49,180 all the complexity of real skin, but real 343 00:11:49,180 --> 00:11:51,820 skin has oil. It has texture to it. 344 00:11:51,820 --> 00:11:52,480 It has 345 00:11:52,940 --> 00:11:54,700 a bunch of properties that are very different 346 00:11:54,700 --> 00:11:57,519 than these idealized plastic like, paint like material. 347 00:11:57,820 --> 00:11:59,899 So so, obviously, for the movies, they want 348 00:11:59,899 --> 00:12:02,559 people to look, you know, natural and appealing. 349 00:12:03,144 --> 00:12:04,664 So that was one that was sort of 350 00:12:04,664 --> 00:12:06,985 a motivation for it. What was interesting, the 351 00:12:06,985 --> 00:12:08,365 discovery was that 352 00:12:08,825 --> 00:12:09,565 most materials 353 00:12:10,105 --> 00:12:13,225 are actually somewhat translucent, and subsurface scatter is 354 00:12:13,225 --> 00:12:15,929 actually more common than just normal surface scatter. 355 00:12:15,929 --> 00:12:17,690 So what happened in surface scatter, which you 356 00:12:17,690 --> 00:12:19,450 learn about in physics, you know, light ray 357 00:12:19,450 --> 00:12:21,769 hits the surface and just gets reflected off 358 00:12:21,769 --> 00:12:24,170 the interface between, say, the air and the 359 00:12:24,170 --> 00:12:26,809 the material itself. Yeah. Yeah. But in most 360 00:12:26,809 --> 00:12:28,809 materials, they're actually dielectric. And by the way, 361 00:12:28,809 --> 00:12:30,410 that's what happens in the metal. You know? 362 00:12:30,410 --> 00:12:32,334 Like, light can't go into a metal because 363 00:12:32,334 --> 00:12:32,995 it's conductive, 364 00:12:33,534 --> 00:12:34,914 so it has to get reflected. 365 00:12:35,294 --> 00:12:38,095 Okay? That's why metals are shiny. But most 366 00:12:38,095 --> 00:12:40,334 materials are dielectrics. You know? They have an 367 00:12:40,334 --> 00:12:42,815 index of refraction. And so most light goes 368 00:12:42,815 --> 00:12:44,815 into the materials. It doesn't get reflected. You 369 00:12:44,815 --> 00:12:46,589 know? You just look at it physically. And 370 00:12:46,589 --> 00:12:48,829 why are the dialectics? Well, they're rocks. You 371 00:12:48,829 --> 00:12:51,069 know? They're based on water. Like, we have 372 00:12:51,069 --> 00:12:53,009 a lot of water in our human body. 373 00:12:53,069 --> 00:12:54,929 You know? They're made of things like fibers, 374 00:12:55,149 --> 00:12:56,449 anything like biological. 375 00:12:57,149 --> 00:12:59,534 And most minerals are not metals. They're, 376 00:12:59,934 --> 00:13:02,095 you know, they're dielectric. So almost everything around 377 00:13:02,095 --> 00:13:03,634 us is a dielectric, 378 00:13:04,495 --> 00:13:06,815 and what happens is the light goes into 379 00:13:06,815 --> 00:13:09,134 the material and then it scatters around a 380 00:13:09,134 --> 00:13:11,054 little bit, and then it comes up. It 381 00:13:11,054 --> 00:13:13,294 looks like it's reflecting off it. Let's actually 382 00:13:13,294 --> 00:13:15,240 go on and scatter around, come out, And 383 00:13:15,240 --> 00:13:17,019 that's called subsurface reflection. 384 00:13:17,639 --> 00:13:19,320 You know, it's been studied, but it's never 385 00:13:19,320 --> 00:13:21,159 really been studied very much in natural no 386 00:13:21,159 --> 00:13:23,799 normal everyday materials like skin or whatever. So 387 00:13:23,799 --> 00:13:25,899 we we develop you know, like a physicist, 388 00:13:26,200 --> 00:13:28,600 you know, just, you know, we read models 389 00:13:28,600 --> 00:13:30,415 about how you might do that. I used 390 00:13:30,415 --> 00:13:33,075 to read books like people like in atmospheric 391 00:13:33,375 --> 00:13:36,254 sciences study that, meteorology study that, like, if 392 00:13:36,254 --> 00:13:38,035 you observe a planetary atmosphere 393 00:13:38,575 --> 00:13:40,335 from a distance, like, it's like you have 394 00:13:40,335 --> 00:13:43,554 this layer of gas around the planet, 395 00:13:43,879 --> 00:13:45,559 and so it's gonna be sort of like 396 00:13:45,559 --> 00:13:47,159 that. The light goes into the atmosphere and 397 00:13:47,159 --> 00:13:48,839 gets scattered. So there, you know, there's things 398 00:13:48,839 --> 00:13:50,039 known about it, but they were all like 399 00:13:50,039 --> 00:13:52,139 things like that, like, you know, planetary atmosphere. 400 00:13:52,519 --> 00:13:54,360 So we yeah. We we just took a 401 00:13:54,360 --> 00:13:56,200 lot of those ideas that they had developed 402 00:13:56,200 --> 00:13:58,085 and and, you know, sort of, you know, 403 00:13:58,085 --> 00:14:00,264 mod used them to model things like skin. 404 00:14:00,644 --> 00:14:02,165 And in the same thing with hair, what 405 00:14:02,165 --> 00:14:03,625 happens is hair is mostly, 406 00:14:04,245 --> 00:14:06,325 translucent as well. It's like a little optical 407 00:14:06,325 --> 00:14:08,165 fiber. And so light goes into it, bounces 408 00:14:08,165 --> 00:14:10,085 around, and comes out. So these just lead 409 00:14:10,085 --> 00:14:12,264 to very different appearances than 410 00:14:12,629 --> 00:14:15,110 metals and things like that. So yeah. So 411 00:14:15,110 --> 00:14:16,230 I I did a lot of work on 412 00:14:16,230 --> 00:14:18,809 on, you know, just modeling different materials. And 413 00:14:18,870 --> 00:14:21,210 the subsurface scattering works, I mean, since everything 414 00:14:21,429 --> 00:14:23,750 looked like plastic, as soon as we wrote 415 00:14:23,750 --> 00:14:26,149 the paper, I mean, every studio in the 416 00:14:26,149 --> 00:14:27,210 world immediately, 417 00:14:28,414 --> 00:14:30,975 adopted them. And we we published the source 418 00:14:30,975 --> 00:14:34,095 code, and it was relatively simple model, so 419 00:14:34,095 --> 00:14:35,855 they could just, like, take it and put 420 00:14:35,855 --> 00:14:36,995 it into their system. 421 00:14:37,454 --> 00:14:39,294 And so yeah. So they like, within a 422 00:14:39,294 --> 00:14:41,389 year or two, everybody was using it sort 423 00:14:41,389 --> 00:14:43,230 of very quickly. And but, you know, it's 424 00:14:43,309 --> 00:14:44,669 it was I think it was the first 425 00:14:44,669 --> 00:14:47,870 time an academic paper had ever gotten an 426 00:14:47,870 --> 00:14:48,769 Academy Award. 427 00:14:50,829 --> 00:14:52,769 What would you say is the most difficult 428 00:14:53,115 --> 00:14:55,995 CGI problem either you've solved or you've seen 429 00:14:55,995 --> 00:14:58,875 someone else solve by some building on your 430 00:14:58,875 --> 00:14:59,375 work? 431 00:14:59,914 --> 00:15:01,455 Well, I I I think the 432 00:15:01,914 --> 00:15:04,095 I think the hardest thing to solve 433 00:15:04,794 --> 00:15:06,554 was not just, like, how to make, you 434 00:15:06,554 --> 00:15:08,940 know, skin look right. I mean, that's really 435 00:15:08,940 --> 00:15:10,160 insane, hard problem. 436 00:15:10,779 --> 00:15:12,639 It's how to build a system 437 00:15:13,259 --> 00:15:14,639 that would include everything. 438 00:15:15,179 --> 00:15:16,620 You know what I mean? Like, it's like 439 00:15:16,620 --> 00:15:18,620 this it's like sort of grand unified theory. 440 00:15:18,620 --> 00:15:21,519 Right? How can I build one rendering system 441 00:15:21,924 --> 00:15:23,625 that would handle any shape 442 00:15:23,925 --> 00:15:27,144 and any material and any light source, 443 00:15:27,605 --> 00:15:28,985 you know, and any kind of, 444 00:15:29,365 --> 00:15:32,165 you know, participating media and and just build 445 00:15:32,165 --> 00:15:34,325 a system that could do it all? And 446 00:15:34,325 --> 00:15:35,605 the problem is you if you if you 447 00:15:35,605 --> 00:15:37,259 can't do a bunch of stuff, like, say 448 00:15:37,259 --> 00:15:38,720 you couldn't do the atmosphere. 449 00:15:39,179 --> 00:15:40,700 I mean, it's just not gonna be useful. 450 00:15:40,700 --> 00:15:42,620 Right? And if you can't do people, it's 451 00:15:42,620 --> 00:15:44,559 not gonna be useful. You can't do plants. 452 00:15:44,860 --> 00:15:46,460 You know, like plants were a huge problem 453 00:15:46,460 --> 00:15:48,300 because there's so many leaves and they have 454 00:15:48,300 --> 00:15:50,460 such complicated scattering, but you have billions of 455 00:15:50,460 --> 00:15:52,559 them. You know? Billions of leaves and 456 00:15:53,035 --> 00:15:55,274 dandelions and stuff. So, you know, just having 457 00:15:55,274 --> 00:15:57,514 a system that could handle all this stuff 458 00:15:57,514 --> 00:15:59,615 and scale to the complexities, 459 00:16:00,475 --> 00:16:02,955 I mean, it's it's mostly an engineering problem, 460 00:16:02,955 --> 00:16:04,495 but it was it was a conceptualization 461 00:16:05,195 --> 00:16:07,610 problem. Like, how do you break down, 462 00:16:08,070 --> 00:16:09,929 you know, the world in some sense 463 00:16:10,389 --> 00:16:12,870 into all these what are some you know, 464 00:16:12,870 --> 00:16:14,070 you know, we sort of use, like, object 465 00:16:14,070 --> 00:16:16,070 oriented, but what are all the objects you 466 00:16:16,070 --> 00:16:18,389 need, and how are they all interrelated? How 467 00:16:18,389 --> 00:16:20,309 do they all work together? And then so 468 00:16:20,309 --> 00:16:22,605 that you can, like, plug in something new. 469 00:16:22,605 --> 00:16:24,205 Like, when we had that skin model, like, 470 00:16:24,205 --> 00:16:25,565 you just plug it in. You know, the 471 00:16:25,565 --> 00:16:27,804 system had the design. So that was actually 472 00:16:27,804 --> 00:16:29,485 my first academy where we had this system 473 00:16:29,485 --> 00:16:30,705 we called Reyes, 474 00:16:31,165 --> 00:16:33,585 R E Y E S, for the California. 475 00:16:33,725 --> 00:16:35,825 There's this park called Point Reyes. 476 00:16:36,740 --> 00:16:38,339 It's a very beautiful place. It was near 477 00:16:38,339 --> 00:16:41,779 Lucasfilm, so everybody knew about it. But it 478 00:16:41,779 --> 00:16:44,259 it was the acronym for renders everything you 479 00:16:44,259 --> 00:16:46,419 ever saw. So, you know, the first thing 480 00:16:46,500 --> 00:16:48,259 what I mostly worked on at Pixar was 481 00:16:48,259 --> 00:16:50,024 just how to build this system. You know? 482 00:16:50,105 --> 00:16:52,105 How how to build a system that renders 483 00:16:52,105 --> 00:16:54,264 everything you ever saw. And, you know, it's 484 00:16:54,425 --> 00:16:55,404 it was very, 485 00:16:56,024 --> 00:16:58,264 very challenging and non trivial to think of 486 00:16:58,264 --> 00:17:00,264 how to design this thing so it would 487 00:17:00,264 --> 00:17:01,705 work. And it's still being used. I mean, 488 00:17:01,705 --> 00:17:03,144 I did this many, many years ago. But, 489 00:17:03,144 --> 00:17:04,904 you know, once you get the basic framework 490 00:17:04,904 --> 00:17:05,549 in place, 491 00:17:06,110 --> 00:17:07,869 you know, you can just keep enhancing it 492 00:17:07,869 --> 00:17:09,630 because you can add stuff to it and 493 00:17:09,630 --> 00:17:11,070 they it just sort of you know, you 494 00:17:11,070 --> 00:17:13,309 have the right design when something new comes 495 00:17:13,309 --> 00:17:15,070 along and just sort of clicks into place. 496 00:17:15,070 --> 00:17:16,670 You know what I mean? So that that 497 00:17:16,750 --> 00:17:18,190 I think that was the hardest part. I 498 00:17:18,190 --> 00:17:20,194 mean, you know, maybe not quite as mathematical, 499 00:17:20,335 --> 00:17:22,515 but just how to conceive of this thing 500 00:17:22,654 --> 00:17:24,595 in a way that, you know, was both 501 00:17:24,654 --> 00:17:27,214 conceptually elegant, but also worked. You know what 502 00:17:27,214 --> 00:17:29,315 I mean? It could be efficient and and 503 00:17:29,454 --> 00:17:30,815 and so on. So that I think that 504 00:17:30,815 --> 00:17:32,759 was the hardest problem. Yeah. What would you 505 00:17:32,759 --> 00:17:35,559 say then is the the most difficult unsolved 506 00:17:35,559 --> 00:17:37,400 problem? What what can't you do now that 507 00:17:37,400 --> 00:17:38,680 you really like to be able to do 508 00:17:38,680 --> 00:17:39,740 in computer graphics? 509 00:17:40,519 --> 00:17:41,880 Well, I think that I have a couple 510 00:17:41,880 --> 00:17:43,400 of opinions. I mean, you know, on the 511 00:17:43,400 --> 00:17:45,340 on the so we would call this photorealistic 512 00:17:45,720 --> 00:17:47,545 rendering and so on. I mean, I don't 513 00:17:47,625 --> 00:17:49,144 I mean, pretty much, you know, we've been 514 00:17:49,144 --> 00:17:50,825 working on it so long. I mean, I 515 00:17:50,825 --> 00:17:52,424 don't know if you go to movies. Some 516 00:17:52,424 --> 00:17:53,705 of the people do, but, you know, the 517 00:17:53,705 --> 00:17:55,865 movies are pretty convincing at this point. You 518 00:17:55,865 --> 00:17:57,464 know? And even like Toy Story was the 519 00:17:57,464 --> 00:17:59,224 first one that we did. It was a 520 00:17:59,224 --> 00:18:00,365 cartoon movie. 521 00:18:00,664 --> 00:18:02,205 Now, you know, you see movies 522 00:18:02,920 --> 00:18:04,380 routinely that just 523 00:18:04,920 --> 00:18:05,900 is completely indistinguishable 524 00:18:06,519 --> 00:18:07,019 from, 525 00:18:07,320 --> 00:18:09,640 you know, from things like Avatar and, you 526 00:18:09,640 --> 00:18:12,119 know, all these movie. So it's pretty hard. 527 00:18:12,119 --> 00:18:13,240 I mean, I don't know if I can 528 00:18:13,240 --> 00:18:14,059 think of really, 529 00:18:14,599 --> 00:18:17,559 one thing. I find natural scenes, outdoor scenes, 530 00:18:17,559 --> 00:18:19,305 sort of still somewhat unsatisfying. 531 00:18:20,085 --> 00:18:21,765 I mean, remember, they still fake a lot 532 00:18:21,765 --> 00:18:23,465 of stuff. They don't model everything 533 00:18:24,085 --> 00:18:25,924 and so on, so they can avoid, you 534 00:18:25,924 --> 00:18:27,865 know, showing you things that they can't do. 535 00:18:27,924 --> 00:18:30,005 But I find, you know, really if I 536 00:18:30,005 --> 00:18:31,865 take a walk in the forest or something, 537 00:18:32,119 --> 00:18:33,960 you know, there's something about it that I 538 00:18:33,960 --> 00:18:35,880 don't I don't see in the computer, but 539 00:18:35,880 --> 00:18:37,240 I can't quite pin it down. That's the 540 00:18:37,240 --> 00:18:39,160 other problem. What? You're you're looking at this 541 00:18:39,160 --> 00:18:40,940 stuff. Like, you look I'm looking at skin. 542 00:18:41,240 --> 00:18:43,240 Like, what are we not getting about it? 543 00:18:43,240 --> 00:18:45,480 You know? There's something underlying the phenomena of 544 00:18:45,480 --> 00:18:47,734 the scattering. So I don't quite know exactly 545 00:18:47,795 --> 00:18:48,615 for these 546 00:18:48,994 --> 00:18:49,494 natural, 547 00:18:50,195 --> 00:18:53,234 environments what we're getting wrong. But, anyway, I 548 00:18:53,234 --> 00:18:54,994 think that's one. But I actually think, you 549 00:18:54,994 --> 00:18:55,494 know, 550 00:18:55,955 --> 00:18:58,615 a more interesting thing is not just photorealistic 551 00:18:59,154 --> 00:19:01,029 effects, but, you know, how to make it 552 00:19:01,029 --> 00:19:02,710 easy. You know, like, I gave a talk 553 00:19:02,710 --> 00:19:05,589 once about starting with Leonardo, how, you know, 554 00:19:05,589 --> 00:19:08,970 we sort of reproduced what Leonardo had discovered, 555 00:19:09,029 --> 00:19:11,349 right, like perspective and shading and all that 556 00:19:11,349 --> 00:19:13,289 stuff, and we just computerized it. 557 00:19:13,865 --> 00:19:15,465 But then the event art sort of went 558 00:19:15,465 --> 00:19:17,785 in lots of different directions. It wasn't just 559 00:19:17,785 --> 00:19:19,865 about realism. You know? So, like, maybe how 560 00:19:19,865 --> 00:19:21,485 to make other kinds of pictures, 561 00:19:22,105 --> 00:19:24,424 like, either more abstract kind of pictures like 562 00:19:24,424 --> 00:19:26,930 an artist might do, or more functional kind 563 00:19:26,930 --> 00:19:28,390 of pictures, like, in visualizations 564 00:19:28,690 --> 00:19:30,529 of things. You know, just how you know, 565 00:19:30,529 --> 00:19:32,609 because there you're not just simulating the physics. 566 00:19:32,609 --> 00:19:34,130 You have to ask but you still you 567 00:19:34,130 --> 00:19:36,049 know, it might be some formal technique. Let's 568 00:19:36,049 --> 00:19:37,589 say we had some theory of aesthetics 569 00:19:38,265 --> 00:19:40,345 or something like that. Maybe we could formalize 570 00:19:40,345 --> 00:19:42,025 that and have a computer do that kind 571 00:19:42,025 --> 00:19:43,384 of stuff. Yeah. You see some of that 572 00:19:43,384 --> 00:19:45,785 generated by AI right now. But, yeah, just, 573 00:19:45,785 --> 00:19:47,465 you know, other there are different kinds of 574 00:19:47,465 --> 00:19:47,965 picture. 575 00:19:48,585 --> 00:19:50,505 And I think we could make a lot 576 00:19:50,505 --> 00:19:52,904 of other interesting pictures besides just sort of 577 00:19:52,904 --> 00:19:53,404 photographic, 578 00:19:53,750 --> 00:19:55,529 You know, sort of a classic thing, like, 579 00:19:55,830 --> 00:19:57,509 first we once we had a camera, like, 580 00:19:57,509 --> 00:19:58,789 you know, what do we why do we 581 00:19:58,789 --> 00:20:00,710 need to you know, we don't want it 582 00:20:00,710 --> 00:20:02,950 to we have cameras to take realistic pictures. 583 00:20:02,950 --> 00:20:05,109 We don't need, you know, artists to draw 584 00:20:05,109 --> 00:20:07,634 perfectly realistic pictures. Yeah. So you're still looking 585 00:20:07,634 --> 00:20:10,115 for the Pixar version of Picasso. Yeah. Yeah. 586 00:20:10,115 --> 00:20:12,455 Exactly. Yeah. Yeah. Yeah. Exactly. Exactly. 587 00:20:13,075 --> 00:20:14,994 So final question. How if you could just 588 00:20:14,994 --> 00:20:16,275 sum it up, how do you think your 589 00:20:16,275 --> 00:20:18,835 training in physics has helped you in your 590 00:20:18,835 --> 00:20:19,335 career? 591 00:20:19,759 --> 00:20:21,359 Well, I certainly learned a lot of phys 592 00:20:21,519 --> 00:20:23,619 you know, physical phenomena, you know, 593 00:20:24,240 --> 00:20:25,059 like transport, 594 00:20:25,519 --> 00:20:26,339 light optics, 595 00:20:26,960 --> 00:20:28,980 and mechanics, classical mechanics. 596 00:20:29,440 --> 00:20:32,085 You know, lots of, particular things I learned. 597 00:20:32,325 --> 00:20:33,924 But the best thing I learned was how 598 00:20:33,924 --> 00:20:34,825 to solve problems. 599 00:20:36,085 --> 00:20:37,684 I mean, you know, I mean, you just 600 00:20:37,845 --> 00:20:39,365 you know, the problems they gave you to 601 00:20:39,365 --> 00:20:40,804 solving, you just had to solve. And there 602 00:20:40,804 --> 00:20:42,404 was a certain way of solving them. You 603 00:20:42,404 --> 00:20:44,404 know? How do you like, you notice I 604 00:20:44,404 --> 00:20:46,484 use the word modeling and simulation a lot. 605 00:20:46,484 --> 00:20:48,849 You know? Like, you have physical models and, 606 00:20:49,230 --> 00:20:51,230 you know, models are useful, but they're not 607 00:20:51,230 --> 00:20:52,509 the whole thing. You have to, you know, 608 00:20:52,509 --> 00:20:54,049 you have to pick the right model 609 00:20:54,509 --> 00:20:56,269 for, you know, you know, like, start out 610 00:20:56,269 --> 00:20:57,649 with really phenomenological 611 00:20:57,950 --> 00:20:59,470 like models, but they can still be super 612 00:20:59,470 --> 00:21:02,049 useful when you also want more fundamental models. 613 00:21:02,174 --> 00:21:03,855 But there's many models, and you have to 614 00:21:03,855 --> 00:21:05,695 pick the right one. And then and so 615 00:21:05,695 --> 00:21:07,394 you just have to pick the right one. 616 00:21:07,695 --> 00:21:08,975 And, you know, a lot of people, they 617 00:21:08,975 --> 00:21:10,735 they just they don't know how to pick 618 00:21:10,735 --> 00:21:12,414 the right model. You know what I mean? 619 00:21:12,414 --> 00:21:13,775 And then you and then you have to 620 00:21:13,775 --> 00:21:14,755 crank through whatever 621 00:21:15,089 --> 00:21:17,569 it takes to sort of make it solvable. 622 00:21:17,569 --> 00:21:19,169 You know what I mean? Like, you know, 623 00:21:19,169 --> 00:21:21,169 it might involve spherical harmonics or it might 624 00:21:21,169 --> 00:21:22,690 involve a bunch of stuff. And then some 625 00:21:22,690 --> 00:21:24,690 of that stuff sort of just difficult. Right? 626 00:21:24,690 --> 00:21:26,769 You just gotta have the the you have 627 00:21:26,769 --> 00:21:29,410 to be, like, powerful problem solver to actually 628 00:21:29,410 --> 00:21:31,434 turn that into, like, something that works. So 629 00:21:31,434 --> 00:21:32,875 I think that's what I learned in physics. 630 00:21:32,875 --> 00:21:34,575 And, you know, that skill, 631 00:21:35,674 --> 00:21:37,674 it was I just think that's why physicists 632 00:21:37,674 --> 00:21:39,434 are so successful when they go to other 633 00:21:39,434 --> 00:21:41,434 fields, is they just have this magical ability 634 00:21:41,434 --> 00:21:43,615 to solve problems in other fields. Yeah. 635 00:21:44,179 --> 00:21:45,700 That kind of fun. Thank you very much. 636 00:21:45,700 --> 00:21:46,679 Yeah. Thank you. 637 00:21:53,859 --> 00:21:57,220 That was Margaret Harris in conversation with Pat 638 00:21:57,220 --> 00:21:57,720 Hanrahan, 639 00:21:58,515 --> 00:22:00,375 who has won three Oscars 640 00:22:00,755 --> 00:22:02,775 in addition to the ACM's 641 00:22:03,154 --> 00:22:04,855 AM Turing Award. 642 00:22:05,154 --> 00:22:07,414 Thanks to both of them for a fascinating 643 00:22:07,634 --> 00:22:08,134 conversation. 644 00:22:08,994 --> 00:22:11,875 And thank you for listening to the Physics 645 00:22:11,875 --> 00:22:13,335 World weekly podcast 646 00:22:13,909 --> 00:22:15,529 in 2025. 647 00:22:16,150 --> 00:22:17,450 I'm Hamish Johnston, 648 00:22:17,750 --> 00:22:20,409 and our producer is Fred Iles. 649 00:22:20,950 --> 00:22:22,089 We'll be back again 650 00:22:22,390 --> 00:22:24,089 in 2026.