Sunday 30 November 2014

Righting a wrong farf

Please read the previous post first, if you haven't done so already. I ended that post with the observation that the wings might bend in the wrong direction. To see whether the opposite looked better, I inverted the warping of the wing and decreased its amplitude as well.

So here is the same farf but with wings that flex the other way. This one is better, I think.


Addition made December 2, 2014

Here's another small improvement: the plants in the background are completely static, whereas they should sway a bit in the wind. That is something Vue can take care of, so after some careful additional programming here is the result. Mind you, the video represents a time lapse shot of the tetropter in flight, and the relative speeds of motion of the tetropter and the plants have not been adjusted yet to look correct in relation to one another. But it works. Somewhere in the future the body of the tetropter needs to become more detailed and more mobile, etc., etc....

Saturday 22 November 2014

The wrong farf (Tetropters VI)

I made a few animations especially for the Loncon3 convention, some of them concerning tetrop
ters (see here for the previous tetropter post). The reason was that I wanted show some of the 'flight platforms' that tetropters could conceivable evolve into. So far, there are the 'standard, 'rowing', 'helicopter' and 'farf' modes.

Click to enlarge; copyright Gert van Dijk

These modes all have to do with the relative amount of movement in all the four ways a tetropter wing can move. The image above shows the idea: there is a general tetropter body, characterised by its vertical position, four jointed legs at the bottom and a head with sensors at the top (there is a head with smaller eyes and a mouth at the bottom end of the body, not visible here). The red, blue and green axes run through the attachment point of one wing and concern the movement of that wing. There are similar axes systems for the other wings, but these are not shown (the wings are, though, just). The arrows indicate the direction of rotation of each axes. A to and fro movement around the blue axis will result in a clockwise and anticlockwise movement. If you combine that with an up-and down movement around the red axis you get interesting patterns: the wing could describe a circle, but the most common pattern is a horizontal figure of eight. The wing moves clockwise and down, then at the end moves up quickly, so it can move down again while moving anticlockwise. That just leaves the green axis, which rotates the wing around its own longitudinal axis, allowing it to achieve the proper 'angle of attack'.

I said there are four ways to move a tetropter wing, and the fourth is not a rotation around an axis as are the first three, but warping the plane of the wing. Well, if you followed that an can envisage it, top of the class. Its more or less what you need to describe the movement of the wings of animals with hovering flight, so we are on common ground here.

I will probably come back to the other tetopter flight modes later, but let's talk about the farf mode. A farf is short for farfalla, the name the Furahan citizen-scientists gave to tetropters with a very long wing base. In fact, the image above has just such a wing membrane: you can see that the membrane lies against the vertical blue axis over its entire length. Actually, the wing membrane shown here would not be an actual one. It is just a rectangular placeholder, but is does show the principle of the thing nicely. This arrangement means that movement around the green axis cannot take place, and to get a good angle of attack the wing will have to warp considerably. If you think this scheme reminds you of a butterfly, you are right: butterflies also have wings with a broad long wing base. In fact, 'farfalla' is Italian for butterfly.

So here is an animation of a farf, made for this post, showing the placeholder wings. Not too bad, is it?

And this is the one I showed at Loncon3, with colours etc. Just about the day before I showed it, it dawned on me that I probably made a mistake in warping the wings. When the wings clap together, they have to be more or less flat, and then they should peel apart, first at the top, and then downwards towards the bottom. Well, that bit worked, but for some reasons I had also warped the wings in such a way that the distal end of the wings –that is the bit farthest away from the body- leans into the movement, so it moves before the part near the body. But the wings would encounter resistance from the air, and so the tip of the wings should probably lag behind the proximal part instead of leading it.

I do not think anyone noticed, but I also did not give the audience a long time to think about it. I will have to do another animation with the opposite effect, to see whether that looks better. But there's no time for that yet... Meanwhile, I hope you still enjoy the 'wrong farf', warped as it is.

Saturday 8 November 2014

Sean's 'spineless' story

With builders all over my house there is still no time to write new blogposts, but I have found a few minutes to bring you the second of my Furaha stories. Those who do not like them need not worry, because these are the only ones I ever wrote. So, here we go, with another glimpse at life in a culture dominated by the Institute of Furahan Biology.

Sean’s 'Spineless' Story

‘Spine Country is not for the spineless’, Sean Nastrazzurro said to a crowd of undergraduate students. They had just come bustling in and had sat down at Sean’s table, which had been the only one with any vacant chairs left. They were sitting on the terrasse of the Bar des Biologistes, where Sean used to go after having given his afternoon lectures, to drink some spiked coffee and also to look at the young female students passing by. The undergraduates had begun talking about the prospects for their first Field Trips, one year from now. Sean had heard countless such conversations, but listened because they he could not help overhearing them anyway and because he was a bit bored. A thin boy had mentioned Spine Country, where Sean had worked for several years. At that point he had decided to join in their conversation. His remark had had the desired effect: they had stopped talking and were looking at him.
‘That’s what they told me when I went there: Spine Country is not for the spineless. In fact, they tried to warn me away from it, when I was up for my Field Trip, as you are now.’
He looked over the rim of his glass at the students, particularly at the girls, to see if they were impressed. They looked at best mildly interested, so he decided to put in a bit more effort.
‘But I didn’t listen, and went anyway. The place nearly killed me on several occasions. I remember three Class IV Danger Situations in the first two years I was there. But what I really learned from my FT was that you have to rely on your own ingenuity, and shouldn’t just go by the Book’.
This was a shrewd move on Sean’s part, because he knew that undergraduates became restless before their Field Trips and always felt that the Institute restricted them too much. The ‘Book’ he referred to was the Institute’s Handbook for Field Trips. It represented the IFB’s hard-learned lessons how to survive in Furaha’s unknown wildernesses, and students were told again and again to go by the Book. In most cases the Book was right: the lessons in it were quite often hard-won, but that didn’t keep the students from disliking it.
‘Tell us what happened, Dr. Nastrazzurro’, a somewhat plump blond girl named Hilde with a tight shirt asked. ‘Did you get to add a Caution?’
In her eyes, adding a ‘Caution’, a cautionary addition to a Rule, was probably heroic hard-won proof of having survived a dangerous situation. Sean looked into her eyes with what he hoped was a wise expression.
‘No, I didn’t. But I can tell you what happened, so you will now that there is more to FTs than going by the Book.’
Sean pulled up his left trouser leg, and bared his leg, which still had enough of a tan from his last holiday on it to look manly. The students all looked silently at the ragged scar running down the side of this leg.
‘See that scar?’ Sean asked needlessly. ‘I got that in Spine Country’.
He dropped his trouser leg and sat back. He could see that he had their full attention now. Hilde leaned forward over the table with great interest. Sean sipped his spiked coffee without taking his eyes away, and nearly spiked his right eye with his spoon as a result.
‘Hmph’, he said, blinking his tears away, ‘Let me think for a minute now’.
This was no exaggeration, because he needed to come up with a good story.
‘Let’s see… Well, I first travelled to Spine Country as a botanist to study thornbushes.’
At this, Hilde backed away a bit with a vaguely disappointed look on her face. Sean, who was indeed a botanist, silently asked himself for the thousandth time in his life why the girls always went for the Carnivore guys.
‘I mean’, he added quickly, ‘that my Professorandus wanted me to study the way thornbushes lock their branches together with their spines, but I did a double task. I also studied the impact of large animals on the Thorn Biome’.
That went down a lot better, as Sean knew it would: ‘Large Animals’ usually got people's attention.    

‘One day, I was very far away from my camp. I had gone out very far, near to Coogan’s Bluff, at the transition between Spine Country and the Hopeless Desert. That’s a place you don’t want to be unless you’re well prepared. Come to think of it, perhaps you shouldn’t want to be there at all. But I had come well-prepared. For instance, I always had my nose filters in. You need nose filters because there are microtetropters there that zoom in on moisture and will burrow right up your nose, if you aren’t careful.’
At this, Hilde turned up her own nose and shivered delightfully.
‘I also wore my protective goggles, and wore my belt with positioning equipment, my emergency medkit and my EK. So, I…’
'What is an EK?’, the thin boy interrupted, the one who had brought up Spine Country in the first place.
 ‘An Emergency Kit, that’s what an EK is. Don’t get caught without one. Now, let me go on’, Sean said, looking reproachfully at the boy.
‘So, except for all the usual tools, such as a corder and a CRM analysis kit, I…’
‘Plant CRM in Thorn Country is similar to Bogorian geneshards, right?’ the same boy asked, who apparently badly wanted to impress the girls. As everyone knew this about complex replicating molecules this feeble attempt did not earn him any respect.
‘Obviously, my dear boy, obviously’, Sean said, to add insult to injury.
He was pleased to see that some the girls frowned at the boy, who seemed to shrink a little. Sean finished his cup and paused to look into it. Unfortunately, none of the students got the hint and offered to get him another one, so he sighed and went on.
‘I was weighted down with all this equipment, and that didn’t even include the sample cases and portable immobilisers to hold the specimina’.
He said ‘specimina’ instead of ‘specimens’, because jargon helped to impress the students. They tended to copy it immediately. 
‘One day, I stopped to drink some water, and set down my pack under a Bruja Tree. I don’t suppose you’ve heard of Bruja Trees?’
They all looked at him blankly, which he took as a sign of interest, which it was not.
‘Bruja Trees, or Knuckle Bushes, are large mixomorphs that compete with desert plants in arid regions.’
Sean started to speak about the mixomorph-plant interactions, and about the way thornbushes curved their spines around one another to create an impenetrable wall. This was something he was really interested in, but he saw that they were losing interest quickly, and changed tack.
‘All of a sudden, a big Thornrunner came out from under some thorn bushes near my shelter’, he said. ‘It looked ferociously at me, and I knew I shouldn’t disturb it, but nobody had told the Thornrunner that it shouldn’t disturb me! Now thornrunners are kind of stupid. They are the only animals that can run through thornbushes, because they are so tough that the thorns can’t puncture their skin. This thornrunner did not like my looks, or perhaps I startled it, but it did its thing: it turned its eyes out of the way and made a run for it. It came straight at me, so I had to jump aside to avoid it taking a bite out of my hide!’
He paused to add drama.
‘I couldn’t jump far enough though, because the ground was covered with footspikes and blister roots. Footspikes are barbed sticks growing out of the ground. Sometimes they are hidden just beneath the surface. If you step on one, it will go right through your shoe and leave a nasty barb in your foot. Blister roots are even worse, because they are poisonous, and even a light touch will burn your skin. Because of them you can’t run fast in Spine Country, because you have to look where you put your feet at every step. So I couldn’t get away from the thornrunner fast enough, and it took a swipe at me and bit a chunk of flesh right out of my leg. I was lucky it didn’t get all four of its jaws around my leg, because it would probably have bitten my foot off entirely.’
Caught up in his own story, he picked up his cup again, only to discover that it was still empty. He looked around at the students, none of whom made any attempts to order him another spiked coffee. Still, they were all looking at him earnestly, except for the thin boy, who seemed to have lost interest. He had dug out a link and had started to work its controls. Sean didn’t much care for him anyway.     
‘That must have been really awful’, Hilde said, once more leaning over the table.
‘What did you do then? How did you get back to camp?’
‘Well, that took some doing, I can tell you’, Sean said happily. ‘First, I started to...’
‘I don’t get it, dr. Nastrazzurro’, the thin boy interrupted, ’You said we shouldn’t rely on the Handbook too much, but what did you do that wasn’t in it?’
Sean was surprised for a moment, at a loss for words. In fact, what he had said earlier about the Book was only meant to get their interest, and he had more or less forgotten about it. He started to think of a reply, but the boy, tapping at his link, beat him to it.
‘This is strange’, the boy said with a frown. ‘I've called up the Handbook’s link version, and I can’t find anything about any thornrunner attacks on humans. I thought animal attacks resulting in injury were all supposed to be on the link?’
The students looked from Sean to the boy and back again.
‘Of course they are’, Sean tried, ‘But you must have the general version there, not the detailed one for local researchers.’
‘Oh no, doctor Nastrazzurro’, the thin boy said in a high-pitched voice. ‘You see, I want to go to Spine Country for my Field Trip, to do research on thornrunners. I want to become a Zoologist.’
Sean began to really dislike him.
‘I have requested access to the full records, and got it. I just linked into them. There is not a single record of any thornrunner attack on a human being on record. Let me see…I’m down to Class VII Danger situations now, but still nothing… maybe if I look for events at Coogan’s Bluff…’.
Sean saw that this irritating spotty pre-zoologist was really spoiling his story, and tried to change tack again.
'Never mind all those old records, let me just get back to my story now. With the wound in my leg, I had to…’
‘Aha!’ the boy yelped, without listening to Sean at all.
He stabbed at the display with a bony finger.
‘There was an incident at Coogan’s Bluff, reported by automatic medsoft. A junior botanist was treated for a stab wound in the left leg, caused by stepping on a footspike! Let’s see, there’s a link to Records… Here it is: there is one reprimand on record for someone not wearing class II leg protectors.’
The boy looked up, a grin on his thin face. The other students seemed unsure what to do. They looked at Sean now, waiting for his reply. Sean knew he was beaten.
‘Oh well’, he said. ‘I might have touched a footspike, it all went so quickly, but only because the thornrunner pushed me aside. And if you wear Class II Leg protectors in Spine Country, you’ll get toerot.’
The students’ expression did not change, even though that bit actually was true.
Sean added: ’Anyway, se non รจ vero, e molto ben trovato.’
‘What does that mean, doctor Nastrazurro?’, Hilde asked. She was leaning backwards now, her arms crossed in front of her.
‘It’s ancient, it's Italian, and it means that it’s a good story even if it isn’t true’, Sean mumbled. The students looked silently into their glasses and cups. Sean sighed and did the same, but his cup was still empty. He stood up, bade the students good-day, and walked to the bar to get himself another cup of spiked coffee. While he waited at the bar he thought to himself ‘No sense of humour, undergraduates don’t have a sense of humour. And I hate zoologists anyway’.