Saturday, 22 October 2011

Lifting the cloak on Cloakfish

There is an odd difference between drawings and photographs of animals. In a photograph a galloping animal may be caught in time in just such a way that only one of its legs touches the ground. No-one will think twice about whether this is 'correct' or not. But do the same in a painting, and people will start thinking that the painter has it all wrong. Something like that happened to my Furahan Fish IV, shown in this blog earlier.

Click to enlarge; copyright Gert van Dijk

Here it is again. I received some questions where it right front fin had gone. Was it amputated or had I forgotten it? No, I replied, I worked out the perspective and the missing fin is simply hidden by the body. I admit that I saw these people's point and have been tempted to tweak the perspective a bit and have the tip of the 'missing' fin emerge from behind the body. Its absence seems to be disturbing in a way. While working on Fish and Cloakfish I experimented a bit with the reasons.


Click to enlarge; copyright Gert van Dijk

This image shows two versions of a ray-like species of Fishes IV. The top image shows a layer for the perspective lines as well as a layer containing some rough idea of light and colour. Layers, for those of you not familiar with computer painting programs, are the computer equivalent of a pane of glass on which you paint. The painting as a whole can consist of many such panes, each consisting a different bit of the painting. The trick is that you can make layers invisible, change their transparency or swap their order. I use Painter 11 as I like its tools, that resemble artists' brushes more than the tools of Photoshop CS5. As you can see from the sketch the perspective effect is fairly strong, meaning that parallel lines diverge quite a bit. Still, the drawing seems to work, perhaps because all parts of the animal are visible.



Apart from 'regular' Fishes, I have been working on Cloakfish, completely unrelated to Fishes I to VI. You will find cloakfish on the main Furaha page, but also here on the blog. Apart from a few sketches almost all my earlier work on cloakfishes involved computer graphics, because I wished to see their four 'cloaks' move while swimming. At present it is time to paint them, but I wished to get their cloaks right, and doing that by hand would be very difficult. So I took recourse to computer graphics, a process best described as 'practical' ('cheating' comes to mind, but why not use tools when available?). To help the process, I adapted earlier programmes in Matlab so I could produce a cloak with any shape I wished, as on the left, that is warped to produce waves progressing along it, as on the right. Right; make four of them, export them as 3D files, import them in a suitable 3D program (Vue Infinite in my case, and we are ready to play.


Click to enlarge; copyright Gert van Dijk

Here is an example. The left panel shows the four cloaks, striped to help visualise their 3D shape, attached to a central axis (that is called a 'dagger', by the way). The body proper is formed by some basic shapes such as cylinders and rectangles. I thought it might be worthwhile to put lots of parallel rods in the image that could help get a better feel for the perspective. I set the focal distance of the imaginary camera in Vue to 35 mm, and that is the image in the left-hand panel. The perspective looks believable, does it not?

The right-hand side was produced in Painter 11. I imported the image from Vue and painted a rough cloakfish on a semitransparent layer above it. I decided to play around with the front edge of the funnel. In that stage of their evolution, cloakfish were all filter feeders, so the opening in the front doubles as a food and a respiratory intake. Some cloakfish evolved feelers, and those are what you see here. I wasn't happy with the sketch though, and wondered whether the perspective was part of the problem.


Click to enlarge; copyright Gert van Dijk

So I went back to Vue, altered the characteristics of the 'camera' to give it a long lens, and repeated the process. Well, well. The result looked more suitable for an illustration that the earlier one, even though that one was realistic. More realistic, because the combination of the lens with the size of the animal resulted in a perspective closer to what you would see if you were a human on Furaha. Obviously, my attempt at 'mathematical correctness' did not work. Perhaps it can be as counterproductive as its political counterpart. Anyway, I was not happy with the funnel opening.

Perhaps it was time for a redesign. Should cloakfish really all be filter feeders? There certainly are small filter feeders on Earth (polyps etc.), but there is curious gap in size in filter feeders: either they are small or they are colossal, such as whales. I cannot think of sardine- or tuna-sized filter feeders. While I haven't thought that problem through, it seems a real one. I wanted cloakfish to occupy lots of niches and needed a good range of sizes. Perhaps the beasts needed a separation of alimentary and breathing tracts after all.

Click to enlarge; copyright Gert van Dijk

Here is an all-new cloakfish. The inner body protrudes forward from the funnel, that, as before, contains the gills. I played with it having four jaws, but decided against it. What you see here is the latest thing in cloakfish design: a regular mouth with a horizontal split. It need not stay that way, though. As you can see, their eyes have shifted forwards on the funnel to improve frontal vision while still having excellent all-round vision. And the perspective? Well, a view without strongly convergent lines, such as this one, may help viewers get a good feeling for the animal's shape.

Saturday, 8 October 2011

From kudu to bogorbes

There is too much going on at present for me to write any blog entries on arcane biomechanical biomechanics on other planets. For once, I will focus on some personal aspects behind a Furahan animal, an idea suggested by two anniversaries of past events. Twenty years ago I visited sub-Saharan Africa for the first time. I wished to see animals in the wild, reasoning that the slow degradation of the world's biodiversity would render such visits meaningless in time. I wasn't wrong about the degradation, but it is not too late for a visit yet.

I had a great time, camping in the wild, seeing animals as they are supposed to be, and revelling in an over-abundance of beauty. Any readers who have been to Eastern of Southern Africa may recognise African influences in my paintings.

Click to enlarge; copyright Gert van Dijk

Here is a sketch proving the point: a group of predators is enjoying their meal on a steppe or savannah, watching some large herbivores and being watched in turn. The scientist in me insists in adding that this is not a typically African scene: similar scenes have been played out on European, Asian, American and probably Australian steppes and savannahs countless times, with different species in the prey and predator roles for each time and place. But it is only in Africa that such biomes have not been wholly replaced by wheat fields, livestock pastures or the human habitat, explaining the strong association of such scenes with Africa. In my case, the associations have a strong personal flavour as well.

That visit changed my life because I met my wife to be during that trip. We got married a few years later, and visited Africa several times afterwards, something I stopped doing after she died, also quite some time ago. At the time she was as enamoured with the wildlife as I was. I returned home earlier than my travel companions, and immediately sent off countless rolls of film to be developed (it was 20 years ago). I sent a few prints to my fellow travellers, and decided to tweak one I would sent to my later wife in Paris, where she then lived.

Click to enlarge; copyright Gert van Dijk

I took out my oil paints and altered a photograph of a greater kudu, an antelope, standing on the shores of Lake Bogoria in Kenya. I added a third pair of legs in the front as well as a new neck and head, and masked out bits of leftover kudu. I varnished the photograph so my handiwork was not too apparent. I sent my 'cooked kudu' to her, and she had a good laugh with it. She mixed the photograph with photographs of her own of that trip. A friend of hers went through her stack of vacation photographs, said "Tiens, il y a six pattes" ("Hey, there's six legs") on encountering the photograph and then simply continued flicking through the pictures, without apparently realising that a large six-legged herbivore was more than just a trifle strange, in Africa or anywhere else...

My wife later dubbed the animal a 'bogorbes' (Venia lauta), and it has been part of the Furahan fauna ever since. You will find it on the cover of Sigismunda Felsacker's travelogue "Paleo Days" (see the New Hades book shop), and the blurb text there was written by my wife; not everyone in the Furaha universe is fictional.

Saturday, 1 October 2011

"Maybe if you stick on another leg at the end of the tail?"

Designing a novel way of walking for extraterrestrial animals is complicated. I tried my hand at designing gaits for large hexapodal creatures (see the main Furaha site), radial walking patterns and also explored walking with an odd number of limbs. In all such efforts the trick is to achieve something that looks interesting as well as believable. In the context of speculative biology 'believable' is balanced somewhere between 'Earth normal' and weirdness. One thing is clear though: you cannot get a believable result by assembling an animal of leftover bits and pieces, such as just sticking an extra leg on the end of a long tail.

Or can you? As usual, evolution on Earth manages to come up with designs that, if invented by a mere human, would fall in the category of unacceptable weirdness. The following video shows an insect that looks odd, but oddness by itself is fairly normal for insects. Look how it moves: most of the time insects walk with a double tripod gait: the front and hind legs on one side move in unison with the middle leg on the other side. When these three legs touch the ground they form a stable tripod. The other three legs meanwhile are lifted and swung forwards, and when they touch the ground, they will form a tripod as well. The two tripods are exactly out of phase, so when one hind leg is on the ground the other should be in the air. Now have a look at the hind legs of this interesting beastie, a trilobite beetle from Borneo. The original is here.

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Its pairs of legs are in phase, a bit unexpected, but slow-moving insects can do that. But that is not all: it uses the tip of its abdomen as an additional unpaired leg. It curves its abdomen forwards, plants its 'leg' on the ground, and pushes backwards with it. Anatomically this may not be a proper leg, but functionally this animal certainly uses seven legs: it's a heptapod!

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Here's another video. The beginning shows that this species can also walk with the front legs out of phase, but you do not get to see all legs that well. It is clear though that it uses the end of its abdomen as a seventh functional leg.

Why do these animals walk in this weird fashion? The gait does not look quick or agile. In fact, the animals appear to be rather slow and clumsy. A bit of research points to an answer. These 'trilobite beetles' are said to belong to the genus Duliticola, and using Google with that name results in a paper starting with the brilliantly surrealistic sentence 'There are two trilobite larva species in Singapore.' Apparently, the male and female of these species differ greatly in shape: the males look like typical beetles while the females are neotenous. Now neoteny is a condition in which sexual maturity occurs while the body is still in a larval stage. The axolotl is a famous example, and humans are sometimes thought to display neoteny as well.

But what does that mean for the strange gait of this apparently female insect? Well, it looks a bit like a regular adult insect, with a hard exoskeleton and all, but its general body shape is in fact that of a caterpillar. Caterpillars display complex gaits, not too surprising if you think about their body plan: six regular legs that will become the legs of the adult insect, a number of 'prolegs' (the knobby stumps further along a caterpillar's body), as well as final 'anal prolegs'. All of these are attached to a boneless body, providing endless opportunities of combining walking with stretching of the body. So that explains the trilobite beetle's walk: its' a caterpillar in disguise. Never underestimate insects' capability of oddness.

There is of course more to be told about caterpillar movement. In fact, at least in some species their gut moves inside their body before the outside follows up. The following video show that very nicely as well as the combination of body stretching with using legs. Perhaps there is a risk that you will learn more about caterpillar movement that you bargained for, but personally, I love details.

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