FLOCK2: A MODEL FOR ORIENTATION-BASED SOCIAL FLOCKING

2024. Hoetzlein, R. Flock2: A model for orientation-based social flocking
Journal of Theoretical Biology, vol 593, 7 Oct 2024, 111880
2024. Hoetzlein, R. arXiv Pre-print. April 27, 2024.
Source code. https://github.com/ramakarl/flock2

Highlights

• A new computational model for bird murmurations shows emergent orientation waves.
• Bird flight is controlled by an aerodynamic model of flight actuated strictly with heading targets.
• Energy and frequency analysis leads to a deeper understanding of model-based flocking.
• Collision experiments demonstrate how high speed flocking birds may avoid interpenetrating flocks.

Abstract

The aerial flocking of birds, or murmurations, has fascinated observers while presenting many challenges to behavioral study and simulation. We examine how the periphery of murmurations remain well bounded and cohesive. We also investigate agitation waves, which occur when a flock is disturbed, developing a plausible model for how they might emerge spontaneously. To understand these behaviors a new model is presented for orientation-based social flocking. Previous methods model inter-bird dynamics by considering the neighborhood around each bird, and introducing forces for avoidance, alignment, and cohesion as three dimensional vectors that alter acceleration. Our method introduces orientation-based social flocking that treats social influences from neighbors more realistically as a desire to turn, indirectly controlling the heading in an aerodynamic model. While our model can be applied to any flocking social bird we simulate flocks of starlings, Sturnus vulgaris, and demonstrate the possibility of orientation waves in the absence of predators. Our model exhibits spherical and ovoidal flock shapes matching observation. Comparisons of our model to Reynolds’ on energy consumption and frequency analysis demonstrates more realistic motions, significantly less energy use in turning, and a plausible mechanism for emergent orientation waves.

My Self-Recovery from Covid with Serious Heart Risk

This is a story of how I recovered from Covid while previously having a major heart reaction to my second Moderna vaccine. I am not a doctor, and this should not be taken as advice, but rather my personal story of how I beat Covid with a serious heart issue without ending up in the ER (again).

Backstory – My Heart Attack after Moderna Vaccine

In 2021, I took my second Moderna vaccine. Four days later I had intense chest pains. Not knowing what it was, I took ibuprofen to sleep and decided if it was still painful in the morning I would drive myself to the hospital. It was, and I went in the next day. After a 30 minute wait in an empty lobby they did an EKG and diagnosed a heart attack. At that point things happened quickly. I was taken by ambulance to a bigger hospital (Lee Healthpark, Ft. Myers), where the doctor wanted to perform a cardio angiography right away. This is the gold standard for detecting obstructions in arteries and veins around the heart and involves a wire physically inserted into an artery that is pushed into the heart where die is injected. The die is imaged by continuous xray. The entry point was my wrist.


Figure 1. Wrist entry point for an expensive cardioangiography. A wire was inserted from this point through the artery into my heart for direct visualization of obstructions. As a healthy, 46 year old, non-smoker, I had no obstructions.

I am convinced that medical practice in the US has become administratively overburdened, yet medically inflexible and dangerous. It’s focus is on risk management for hospitals over patient care. If there is a conflict between these the hospital wins. Doctors must follow a script provided by insurance companies for exact steps on the order of procedures. This makes obsolete any discussions with the patient about history or sensation. I told the doctors that I was physically fit, age 46, never smoker, exercise regularly, and the chance of an obstruction was extremely low. The cardio doctor suggested the $25,000 cardioangiograhy as my only option. I don’t believe he was seeking to understand the whole problem, just this narrow aspect of possible obstruction related to his area of expertise despite how unlikely. I think he enjoyed preforming the procedure, referring to his cardo ER as a “racing pit”, and his team as a “pit crew”, which has the effect of objectify the patient as.. a car (rather than a person). The cardioangiography showed no obstructions.

Figure 2. Echocardiogram performed the following day. This procedure could have been done first, and might have revealed something if observed before nitro medication.

An echocardiogram could have been performed first but wasn’t. This was done the following day. At the time I was diagnosed with Takotsubo cardiomyopathy, and this non-invasive test may have been able to identify the Takotsubo cardiomyopathy early. Interestingly the classical heart shape for Takotsubo was not observed in the echo on the next day. I am convinced that doctors really do not understand the heart effect of Covid or Covid vaccines. I had no better understanding of what happened.. and was sent home with Tylenol.

I believe Covid upsets the medical protocols of insurance companies and hospitals. It is not well understood, while defying the modernized flow-chart approach to medicine.

That’s how this all started. A non-obstructive heart attack, despite not seeing the classical octopus shaped heart muscles in an echocardiogram done the following day, although the heart attack may have passed by this time. I was considered high risk for complications and told the benefits of further boosters we too risky for me.


Figure 3. Positive Covid-19 FlowFlex test on January 8th, 2023.

My Self-Recovery from Covid with a Serious Heart Risk

But this story is not about my heart condition, its about how I recovered from Covid without ending up in the ER again. Using actual knowledge and what I believe doctors should do.

I was able to avoid Covid for two years. Then on Jan 8th, 2023 after feeling extremely sick, I tested positive for Covid-19 (FlowFlex rapid test). I knew it was real because my heart rate jumped to 135 bpm and didn’t come down for the entire day. I felt extremely cold, chills, had a fever, and felt worse than any sickness I had experienced before.


Figure 4. A FitBit tracker shows my heart rate on my first day of Covid-19 (left), and the gradually decline in peak heart rate the following day (right). In the left figure you can see that my heart rate peaked at over 145 bpm and remained above 130 bpm throughout the day despite the fact that I was doing nothing more than sleeping or laying in bed.

I knew that I had to rest my heart immediately, and with two blanket layers, went to sleep for 14+ hours.

Why not the ER now? I was at high risk. Yet, I did not have chest pains (like before) and I knew if I could calm my heart that would be heading in the right direction. I didn’t yet feel an emergency was happening. Despite feeling crappy, having no appetite, unable to do anything standing for even 10 mins, I knew that everything must focus on relaxing and maintaining my heart. It must rest and recover.

Here’s what I learned for myself..

Fresh air is absolutely essential. The purpose of the heart is to move oxygen, from the lungs to the rest of the body. Covid is making that harder. Pulmonary cough even more so. More oxygen allows the heart to work less hard. I fully opened the window in my room, both day and night. I kept this as a hard rule. Oxygen!

Understanding oxygen in air: https://www.ictinternational.com/casestudies/understanding-oxygen-in-air/

Globally the air holds 21% oxygen on average. Humid air, such as in Florida, holds less oxygen. The percentage reduces to 18% oxygen in air when the relative humidity is over 80%. The oxygen percent drops another 2% if the temperature goes over 100 degrees. So on a hot, humid day, the oxygen in air is doubly reduced.

Did you know that your own exhaled CO2 builds to impairment levels when sleeping in a fully closed, non-ventilated room?

Sleeping closed room indoor CO2 analyzed: http://vair-monitor.com/2016/09/29/sleeping-closed-room-indoor-co2-analyze/

Indoor carbon dioxide levels could be a health hazard: https://www.theguardian.com/environment/2019/jul/08/indoor-carbon-dioxide-levels-could-be-a-health-hazard-scientists-warn

CO2 is measured in parts-per-million (ppm) and just 1000 ppm can cause impaired thinking, while 5000 ppm is considered dangerous. CO2 can easily rise above 1000 ppm at night in an unventilated room. A ceiling fan does not help because it just circulates the air rather than bringing in fresh air. I needed as much oxygen as I could get! The windows stay fully open.

Proper tools. I knew this would not be a typical Covid recovery. The heart is a subtle thing that we aren’t usually aware of – hence the study of medicine. I knew that I could not rely on my “feeling” or sensation alone for something so critical as my heart. Here is what I had or acquired:

  • Fitbit watch ($100) – Continuous monitoring of heart rate during day and night, extremely valuable.
  • Wrist BP monitor ($40) – Check BP as needed
  • Finger Pulse Oximeter ($22) – Measure oxygen efficiency in the blood.
  • These aren’t proper tools by medical standards but they are for my use. That is considering both the quality and cost. A Fitbit watch and wrist BP used correctly perform the main tasks I needed them to – measuring how hard my heart is having to work.

    I consider these essential tools for monitoring the heart. One could have a heart rate of 80 bpm yet a blood pressure of 150/100 or 100/60 would be dangerous. Together heart rate and BP tell me how hard my heart it working. To make the heart work less, it’s all about the oxygen, so the PulseOx measures that conversion efficiency of the lung as a percentage of oxygen bound to the blood. I could determine what to do based on these measurements rather than a guess or feeling.

    Don’t exercise. There is a school of thought that says you should do light exercise during Covid recovery. With a heart condition the conclusion I came to is don’t!. Just a few minutes walking pushed my heart rate to 120-130 and made me feel faint. Give it time, let my heart heal, let it recover and let my body learn how to deal with Covid. Rest first above all else.

    Temperature regulation. With the window fully open for oxygen, I needed to control my temperature. In January in Florida it was cold at night but hot during the day. Two heavy blankets worked well, that I could layer or unlayer as needed. This helped drop my fever.

    Cough control. Coughing is a difficult issue because it may be a lack of oxygen causing the cough (dry cough). Combine that with a pulmonary infection and it could make it very difficult to breath and sleep (mucus producing cough). I found the most important thing is don’t bury my head in the heavy blankets. While comforting, there’s no oxygen under a blanket. When I sleep on my side, I feel my lungs are compressed, and the cough is worse because airways are blocked. So I learned to sleep on my back, lungs flat, even if I do turned my head to the side. Pushing the blanket close to the side of my head, but not obstructing my face, helps me to feel I am sleeping sideways even though my back and lungs are laying completely flat. If I need even more air, I stretch my head up, making a straighter airway to my lungs.

    Lots of water. With heavy blankets, I was sweating profusely. The FDA recommends that men drink a full 3.7 litres (1 gallon) of water per day when we are healthy!. Despite how abhorrent anything tastes, even water, I knew that I needed to drink at least a full gallon every day. One day I missed a water session before afternoon nap and and woke up incredibly dizzy, that was the closest I came to thinking a heart attack was imminent (but still no chest pains). But I drank water and laid down immediately. If I felt incredibly terrible at any time, it was most likely water, and drinking two glasses usually resolved it.

    Food. This is tricky because I had no appetite and knew that some foods would just make me sick. I found that the best were fresh fruits (containing more water) and some soups. Others have suggested gatoraid and green tea. Gradually I found I could add more foods to build strength, and this made sense as I recovered.

    Tylenol (acetaminophen). I now accept no other pain meds due to my heart condition. Ibuprofen, Tramadol, etc. all have possible heart interactions that can raise or lower blood pressure. Not taking any chances. Tylenoln is know to reduce pain while also stabilizing heart rate and pressure. If I have trouble sleeping due to a cough, I take Tylenol.

    Careful self-monitoring. During this entire time I was monitoring my heart closely. What was my heart rate?, my blood pressure?, my PulseOx? Were they in reasonable ranges or at least getting better? Did I feel any acute chest pain that might suggest a heart attack? Everything was focused on easing the stress on my heart, first with fresh air/oxygen, then with limited activity and plenty of sleep. Everything else was secondary despite how uncomfortable it was.

    Fortunately this careful approach worked for me. On day 1 of my Covid recovery my heart rate stayed at 135 bpm the entire day and even while sleeping, yet with normal BP. My Fitbit recorded a 17 hour sleep, that must be some kind of record. On day 2 my heart rate averaged 100 bpm including during sleep, where my typical nightime heart rate is 65-70. So I knew that my heart was still working too hard. However, it was still dropping, by day 3 my heart rate dropped to high 90s.

    I felt a bit better at this point, but if I tried to get up a do something even for 10 mins my heart rate would jump to 140 bpm. I wasn’t in the clear yet. I knew that I just need more rest and sleep until my body could figure out how to fight Covid and my heart could get back to normal. It’s all about oxygen, rest, and water. I had two rounds of Moderna vaccine so my outcome should be better than being unvaccinated.

    Reflections on our Medical System

    I truly shudder to think what would have happened if I went into an ER.

    Do I think any of the above things would have happened in a calm, considerate way, focused on these basics and easing patient stress toward healing?

    Not a freaking chance! My own past experience has shown, repeatedly, that hospitals are about efficiency and risk mitigation and I don’t see any efforts in the medical community to address these fundamental failures. I believe the most important factors in my recover were oxygen and decent rest. In an ER oxygen would be administered directly but good rest depends on comfort, lack of interruption and calm – things that ECU (Emergency Care Units) at hospitals often forgo due to risk management practices – hourly blood draws, cold rooms, excess lighting, monitor noises. Science-based methods, flow chart medicine, nurse shortages, and rising patient numbers have nearly eliminated the concepts of patient dialog and comfort as factors in care and recovery (unless you have money). Understaffing makes these challenges more difficult.

    Back in 2021, the doctor who did the original wrist-entry cardioangiograhy, asked me to stay overnight in the hospital to monitor me. My heart attack symptoms and chest pains were reduced earlier that day due to use of nitrous meds. However, after the tests he “forgot” to prescribe any pain meds that evening, and I woke up in the hospital at 2am with the same chest pains that I went in with during the heart attack. It took 2 hours to find, and get approval (?), from another doctor to get new chest pain meds – I was probably having another heart attack. Meanwhile I was in a cold room, with thin blankets, while nurses woke me every 2 hrs attempting to draw blood from shivering vein-constricted fingertips, because I was told that two easily accessible IVs put in earlier could only be used by the doctors. Can we not invent a machine that pulls a small amount of blood through an IV while you sleep and tests it discretely? Why draw blood so frequently? Risk management. I believe overnight stays in the ECU are only there to prevent a major emergency, but may in fact make the situation worse since that don’t focus on symptoms and recovery. In my experience it wasn’t for care; I didn’t sleep at all due to the cold and failed blood draws.

    I was only able to talk to the cardio doctor a total of 15 mins, 5 mins when he first insisted on the cardioangiography and 10 mins when they sent me home with Tylenol. My impression is that he didn’t really listen to a single thing I said.

    Doctors wonder why patients take to self-learning and online knowledge. The reason should be very clear, our medical system is failing the patient in favor of the hospital, the insurance company, and the system. Patients in the US deserve a better system. Listening, patient care, comfort, history and communication should happen with science and risk management, not exclusive to these.

    This recent story began when I went on a two week trip over the 2022-2023 new year, for me, a long time to be away from my 15-month old daughter Camellia. Covid was diagnosed by rapid test toward the end of my trip. When I came back I went directly into home quarantine for Covid. She wasn’t even aware I was back, since my room door was closed, and I kept quiet not wanting her to be exposed to me. She doesn’t know I am here, but I know she is there. I can hear her playing.

    Update:
    On April 21st, 2023 I experienced a very serious episode of food poisoning. I had vomited six times, and woke up at 2am with a heart rate of 170 bpm, and extreme sweating. Whereas my actual Covid-19 positive sickness from January 2023 had resulted in a serious cough and high heart rate, I did not experience chest pains at that time. However, during this food poisoning in April 2023 the chest pains were extreme. I am familiar with digestive-related chest pains, which feel like a pressing, bubbly pain from the stomach upward. This chest pain occured a few days after the primary sickness. The chest location was much higher, in line with the clavicles, and spreading across the chest from the center. The chest pain was intense enough to cause dizziness and blurred vision. Yet my heart rate and blood pressure had dropped to normal by this time. I am suspicious that these chest pains may be a form of long term Covid, where any type of sickness will induce a heart-attack like chest pain.

    The question for cardiologists is this: What could cause an upper chest pain and dizziness yet not be a heart attack? Is there the possibility that long-term Covid-19 symptoms could cause this, and if so what are the mechanism and proper treatment?

    PS. I am not against medical science per se, and especially the modern benefits of technology and medicine. This article calls out specific systematic practices by insurance companies, hospitals and by doctors that have, in an extreme sense, shifted away from actual patient care and recovery.

    A Procedural Model for Diverse Tree Species

    Rama Hoetzlein
    13th Procedural Content Generation (PCG) Workshop, Sept 5-8th, 2022

    A Procedural Model for Diverse Tree Species, Pre-print
    A Procedural Model for Diverse Tree Species, Talk Slides
    Procedural Content Generation Workshop, 2022 Papers

    Abstract

    The modeling of trees represents a unique and classical challenge in computer graphics. Models of 3D trees must express the form, complexity, structure, growth and diversity of real trees. Presently the most common methods for the modeling of 3D trees include a) user-based creative modeling, b) direct geometric capture such as LIDAR and photogrammetry, or c) indirect methods such as machine learning from images. These techniques often require significant human effort, large amounts of data, considerable computation resources, or any of the above. While there are methods that consider the direct procedural generation of trees, current models often require some human supervision to focus on naturally plausible variants. Instead, our approach is to construct a botanically inspired, harmonic, procedural model for trees which directly produces realistic yet diverse trees.

    Knowledge Cultures in New Media Art

    Rama Hoetzlein
    ISEA 2022 International Symposium on Electronic Art, Barcelona, June 14th, 2022

    Knowledge Cultures in New Media Art, Paper pre-print
    Knowledge Cultures in New Media Art, ISEA Talk Slides
      Knowledge Cultures in New Media Art, ISEA 2022 Publication page

    Knowledge Cultures examines the many creative sub-groups in New Media Art and seeks to identify their explicit, hidden or shared ideological principles. This paper defines knowledge cultures as flexible, overlapping, non-exclusive, ideological sub-groups and seeks to identify such groups within the practice and theory of New Media Art. While practicing groups may be associated with specific media such as games, 3D printing, or artificial intelligence, we seek to identify knowledge groups by their explicit, hidden or shared ideological principles.


    Allegory of Forests

    48″ x 96″, Oil on canvas

    EXHIBITIONS
    2019, FM Oakland Studios
    2020, The In Art Gallery, Director’s Award (winner)

    The Allegory of Forests expresses connections between humanity and nature across vast distances compressed into the space of the canvas. Oil painting in large format allows me to explore meaningful spatial relationships not possible with photography. The forest fire, the secluded forest, the river, the glacier and the mountain coexist in a single space where these might be distinct photographic experiences. These domains are not simultaneously visible in reality but are connected in actuality.

    The forest fire references those of the immense Camp Fire that destroyed Paradise, California in 2018 (wiki, photos). The fire was originally painted in reds and oranges when I discovered the partially unfinished white of the canvas lends an intense brightness similar to the real event. Titanium white is then used directly to complete the surface, giving the appearance of the canvas itself consuming the building structures.

    People are absent; their impact is implied; our objects remain to represent us. The absence of people is also indicative of tragic unease and disaster. During the fires, the entire SF Bay Area and California valley sheltered to avoid smoke while the residents of Paradise abandoned their town. Without the presence of people our buildings and vehicles appear unnatural and out of place.

    Meanwhile, in remote places, horses and other animals live out their lives only remotely aware of human tragedy and its natural impacts. The effects, carried over great distances, are nevertheless persistent. Glaciers drip away in the distance (link). This ecology is lived and enacted within the space of the canvas.

    Rama – Holiday Wish List

    Hey Family & Friends,

    I realize it can be difficult to find a gift for me. I don’t need much and have what I need. I created this page by request and suggestion. Rather than make you guess, this is a list of stuff that you might think that I normally have, but don’t because I always feel like I can just put it off. Small, useful things most people have that I find tedious to go buy. I really would appreciate these, I just don’t want to admit it 🙂

    Every item here should be less than $40.

    1)

    1″ Butcher Block cutting board.

    Good cutting boards are hard to find. Less than 1″ will warp and buckle, and if not sealed properly they get moldy. A well-made, designer cutting board cost over $100 – don’t get! It’s just a nice piece of wood! I would make one for myself if I had the time. Minimal, wood, nice, thickness is key.

    2)

    Knife Sharpener

    Could really use one. But mostly don’t get one out of principle because I refuse to spend over $50 on a knife sharpener. Please don’t get me something on the right – these look fancy but will cost too much and break. A knife sharpener is simply a whetstone on a solid base (left). An antique shop might have one for $10.

    3)

    Electric Hair Clipper

    I’ve had mine for like 10+ years, but its reaching end-of-life. I haven’t been to a barber in same length of time – cut my own hair. Don’t need a close (screen) shaver. NOT cordless or battery, should plug in. Simple is better. $30 kits come with multiple depth attachments. Just always put it off because current one sort-of works, and I’ve fixed it like 3 times.

    4)

    Serving Trays

    I always thought it would be cool to have serving trays, so I could bring guests wine, or cheese, or whatever. I just never get around to it because I rarely have guests. But when people do visit, I wish I had these. Simplicity is key. Not fancy. Real bamboo, wood or metal. No fake materials.

    5)

    Decent, 7-port, Powered USB 3.0 Hub

    A simple, decent, powered USB hub that has 7 ports, with 900 milliamps per port for USB 3.0. Nothing fancy. Needs to provide enough power to supply three external hard drives. Not flakey.

    5)

    Shirts

    Ok. 🙂
    Just a warning, I have very specific tastes in clothing, so you’re getting in deep now.
    This will be a short introduction to men’s shirts. Proceed at your own risk!

    If you’ve made it this far, you must be serious.. Getting cloths as a gift for a man – that won’t be exchanged – is very hard.
    – I am always in need of nice shirts.
    – Not pants, not sweaters, not socks, not coats. Shirts.
    – NO flowery shirts, NO plaid, NO paisly, NO stripes, NO checkers.
    – NO bright colors, NO crazy designs, NO biker tats, NO logos, NO words really.
    – This isn’t to say other guys won’t appreciate them, they’re just not my style.
    – NO long sleeve! I live in Florida.
    – The hard part is that too many shirts ‘try too hard’ to be cool. Here are examples of shirts NOT to get me:

    – What I like are plain, solid and pastel colors, possibly with nice edging.
    – It’s very difficult to find nice shirts.
    – The proper name them is: mens casual short sleeve collar shirt, slim fit, size medium.
    – Here are some good ones.

    Those are two of my favorite shirts. Only $20 each.

    – My best shirts are Danish, Swedish and Nordic, but designer shirts are too costly. This one was $120 overseas. But please don’t try this – buying European is a very personal process, I prefer to do myself. Notice it has a micro-pattern, with custom trim, and a local Dutch label, which you can’t find online. I only have one like this:

    – Micro-patterns are interesting if they look solid from a distance.


    This photos is from a Johnston & Murphy catalog. You can see a nice shirt design is very thought out.

    – Here is the current set of shirts in my closet. Unfortunately, there aren’t enough colors, because colors are too often excessively bright and loud. I wish I had more subtle colors or micro-pattern. I like edging and colored threading (where the seams are done in a visible colored thread)

    – Where to get shirts? Good shirts can be found at.. H&M, TJ Max, Kohls, Dressman, Guess, all for less than $20. Slightly higher up is Johnston & Murphy. I won’t go more designer fashion than that unless I travel.

    Now you know something personal about me.

    – As a professor… a good shirt says to your students: “I’m not trying to please you, I’m not joking, not kidding around, I’m not your parents, I’m not too cool, I’m not ancient, I’m not cheapo, I’m not poor or rich.. I’m just your teacher.. But I know how to dress.”

    You know, you could just get me a cutting board.. 🙂

    I feel that a genuine gift is something where you learn something about that person to really understand them more deeply. But if I haven’t seen you in years – and I am a private person – it could be very difficult to find out about me. Before I would never write this page. But my thinking now is that I want to try and reduce your unexpected gifts that might contribute to landfill. So here is a list of things that I don’t want..
    DON’T GET ME:
    – Please don’t get me trinkets or desk items. These will end up in my “hide forever” drawer, only to come out to prove to you I still have them.
    – Don’t get me humorous or joke items. Unless it is an inside joke that just you and I can appreciate.
    – Don’t get me large items. I prefer minimalism and open, uncluttered spaces.
    – Don’t get me delicate things. On the airplane or in shipping they will break. Will also end up in hide drawer.
    – If you really want to get me a creative, sentimental gift, then you really need to know me well enough to know what themes I like. Since I don’t share often I can see how this would be hard.

    Simple, functional, household items is your best bet, because they will serve a purpose without adding to waste or to the hidden items box. But not random. I don’t need a tomato slicer because a knife if just fine. See list above.

    Anything functional above would be just perfect. Less than $40.

    I enjoy a simple life. I like things to work nicely, yet often postpone fixes out of principle or refuse to give into costly, cheaply made products.

    If you’re on this page, now you know 🙂

    Sincerely,

    Rama

    Race to Virtual Reality:
    The Future of VR Headset Visual Acuity

    The release of the Oculus Rift DK1 in 2013 brought Virtual Reality to the mainstream, again. With low latency and 110 degree field-of-view, for the first time this offered a reasonably priced VR headset that doesn’t make people nauseous (for most). Since then companies such as HTC, Samsung and Oculus have entered and propelled the VR Headset market forward. None-the-less building a good VR Headset is a difficult challenge as consumers expect high resolution, wide field-of-view, low latency, and decent contrast.

    To understand trends in VR Headsets we look at visual acuity as measured in pixels per degree (ppd). While other measures are also important, such as field-of-view, this metric indicates the visual density of the device – a strong factor in the perception of quality and reduction of the pixel grid effect. Although this market is still in very early development, analysis of VR Headsets from 2013 to 2019 shows a roughly linear growth in ppd (left side of image). The Oculus Rift DK1 from 2013 has an acuity of 5.8 ppd, whereas the more recent Gear VR from 2019 has an acuity of 16 ppd.

    Meanwhile, looking at recorded 360-degree Video Content (right side of image), we see a trend from 2K to 4K in the past 5 years, with the future looking at 8K content. There is currently very little 8K video content but that is expected to change. More importantly the technology for 8K video recording and playback is now possible. With a 360 degree field-of-view 8K video content contains an acuity of 22 ppd, surpassing the most modern headsets. In other words, even with the best VR headset you won’t be able to make out all the details found in an 360-degree 8K video.

    Human vision has an acuity of 60 ppd – up to 12,000 pixels across a 210 degree field-of-view. A linear trend shows that VR Headsets will slowly inch their way toward this goal, depending primarily on the OLED and related markets to push higher screen pixel densities. At the current rate, we can estimate that VR Headsets may match human visual acuity by the year 2070. Thus you might not want to wait for the “perfect” headset as it could be a while. In the meantime factors such as field-of-view, low latency, contrast, tracking and interaction will provide a great deal of variety in the market before we get there. By 2100, a century from now, people could be enjoying VR experiences as richly detailed as waking life – hopefully with sunglasses instead of heavy headsets.

    Essential Resources for Understanding Global Change

    The following are a set of resources to help understand modern global change.

    This list of essential resources is intended for the general public and presents important authors across major fields of study that everyone should know.

    Resources were chosen based on their relevance to global issues, the importance of its contribution to other fields, the importance of concepts to raise public awareness, and clarity of presentation or writing to a public audience.

    Field Author Media Resource
    Climate Greta Thunberg Interview School Strike for Climate: 15-Year-Old Activist
    Speech Writing Save the World by Changing the Rules
    Womens Rights Tarana Burke Lecture Me Too is a movement, not a moment
    Rituparna Bhattacharya Paper #MeToo Movement: An Awareness Campaign
    Policy Alexandra Ocassio-Cortez Interview Rep. AOC Explains Why the Green New Deal is About More than Climate
    House Resolution The Green New Deal
    Labor Elizabeth Warren Lecture The Coming Collapse of the Middle Class
    Paper The Growing Threat to Middle Class Families
    City Planning Elon Musk Interview The Future we’re building – and boring (tunneling)
    Computer Science Lee Sudol vs. AlphaGo Documentary Film AlphaGo (Artificial Intelligence)
    Biology Marla Spivak Lecture Why bees are dissapearing
    Paper The Plight of the Bees
    Energy Michael Shellenberger Lecture Why renewables can’t save the planet
    Book Break Through: From the Death of Environmentalism to the Politics of Possibility
    Relationships Esther Perel Lecture Rethinking infidelity.. a talk for anyone who has ever loved
    Miller McPherson Paper Social Isolation in America: Changes in Core Discussion Networks in over Two Decades
    Education Davis Guggenheim Documentary Film Waiting for Superman
    Hannh Ardent Paper The Crisis in Education

    by Rama Karl Hoetzlein and Andy Hacket

    Full document (CC-BY):


     A Practical Guide to Rudderless Sailing

    Why sail rudderless?

    We believe that rudderless sailing allows the novice sailor to improve boat balance, sail trim and centerboard control much more directly. The rudder provides a guarantee for your point of sail whereas rudderless involves maintaining your point of sail by understanding and feeling all the forces on the boat. Aside from its help in managing rudder failures, we believe that rudderless gives the sailor a better intuitive sense for how to trim and balance a boat; which is valuable for performance sailing, sail trim and general good form.

    A few motivations for this guide. First, we’d like to mention Joel Brand’s e-book Rudderless Sailing from 2013 as an excellent review of rudderless sailing theory. We are also inspired by Harry Morton and Israel Smith’s youtube video “29er No rudder sailing with Dave O’Connor” from 2012 which demonstrates two-handed rudderless on a small 29’er – with a spinnaker! Pretty amazing sailing, and still one of the few videos of rudderless with tacks and jibes. This isn’t to say there aren’t many great rudderless sailors. Yet we feel the lack of examples is because it is currently viewed as an extra skill rather than as a form. We hope to change that.

    The primary reason for this Practical Guide to Rudderless is to provide a starting point for any club or novice sailor to learn rudderless as a way to intuitively feel the forces on the boat. While we briefly touch on theory, our focus is on a practical guide that helps you to understand what is happening when you’re on the water. Of course nothing can replace actual sailing. So our intention is to give you an idea of what you’re likely to experience, the tools you have to respond to it, and exercises to help you gradually improve.

    This was a senior project with the Cal Sailing Club in Berkeley! Thanks for their support!

    Questions & comments
    Both are welcome below! We’re happy to provide this and hope to improve it.

    PROCESS

    VOX3 is a stereolithographic 3D printer with a voxel-based workflow. Stereolithography, or SLA, 3D printing uses a photosensitive liquid polymer to create hardened layers of material. Whereas laser SLA exposes each layer by tracing the outline of the part with a laser, projector-based SLA exposes a single layer all at once. This process is most similar to the Formlabs desktop 3D printing process.

    WORKFLOW

    The unique aspect of the VOX3 is a voxel workflow based on the NVIDIA Jetson TX2. A typical workflow for 3D printing is to model a part with polygons, then load the part on a CPU host which performs voxelization and then generates either G-code or the slice images required for SLA printing.

    By running GVDB Voxels on the Jetson TX2, we are able to perform advanced processing in the printer itself. The Jetson TX2 has dual video outputs, enabling it to run the slice projector and a preview monitor. Using 256 parallel CUDA cores, the Jetson TX2 can process polygonal and voxel models on the device. This workflow implies the ability to transmit, process, in-fill and slice volumetric data directly on the 3D printer.

    The VOX3 workflow allows for live processing of the part during printing. Although not used in our prototype, feedback from the printer via cameras and sensors could be sent to the Jetson to make live adjustments. Additionally, re-processing can be performed since the VOX3 has full access to the original and voxelized model in printer memory. In our demo the VOX3 takes a polygonal model as input, performs full, high resolution voxelization to a sparse 3D volume, and computes each cross sections on-the-fly as needed for projection while printing.

    DESIGN & CONSTRUCTION


    Figure 1. Frame assembly

    The VOX3 was designed as an experimental prototype. The process of bottom-up SLA printing requires a projector, a built tray, a moving build platform and a mold release mechanism. Figure 1 shows the basic frame assembly. The Z-axis and build platform are controlled with a leadscrew and a 1A stepper motor. The front mounted motor is used to tilt the build tray after each printed layer.


    Figure 2. First projection test

    With the frame designed as two stacked aluminum cubes, the projector is mounted in the lower cube and points upward at the build tray. Figure 2 shows the first projection test.


    Figure 3. Completed VOX3 printer

    The completed 3D printer is shown in Figure 3 with the Jetson TX2 (panel top left), and a Smoothieboard (panel bottom left) which controls the two stepper motors. Special UV transparent glass (center) is required so that the projector light has sufficient power density to polymerize the SLA liquid. The build tray holds the liquid, not shown in this photograph.

    RESULTS



    The VOX3 was exhibit at the 2017 GPU Technology Conference as part of the NVIDIA display on Optimized 3D Printing with the GVDB Voxels software. Since resin printing can be messy and requires refilling, the display was operated in demo mode which shows the moving printer head and 3D slices computed in real-time.


    Also exhibit were 3D printed parts made by Voronoi in-filling with GVDB Voxels. The Lucy model was printed as both a solid part and with voronoi filling to demonstrate weight reduction computed interactively and entirely with voxels.