Saturday, 26 December 2015

The Return of the Common Cloakfish

From time to time I find that my self-imposed restriction on not doing any Furaha work except working on The Book begins to chafe. I know that animations cannot feature in a book, but they are fun if very time consuming, and that holds for blogging too. So I gave myself a short vacation from painting and went back to an old favourite: cloakfish. The type of cloakfish shown in this blog previously as well as in this particular post is by now a primitive one. More evolved cloakfish have shown a considerable adaptive radiation: bodies were squeezed, cloaks either merged with the body or were stretched, etc., etc. There are now 'short sleeved' cloakfish as well as 'long sleeved cloakfish'.  The protocloakfish I will show in this post is a long sleeved one: the cloaks are considerably longer than they are wide.

The novel feature I wished to explore had to do with cloak movement. Until now, the cloaks moved with waves undulating backwards over the fin, pushing the animal forward. If you look closely at squid and cuttlefish, Earth's own indigenous aliens, you can at times observe that there seem to be several waves travelling over their fins at the same time: let's call them major waves and minor ones, and each set seems to be controlled independently. Here is a YouTube video showing squid movement: most of the time you see just one type of wave, but at times the pattern changes. I would not be surprised to learn that fin control in cephalopods is neurologically quite complex. I really must look up what I can find about that in my books on cephalopods (yes, I have more than one book on cephalopods: every self-respecting geek with an interest in speculative biology should devote part of a book shelf to cephalopods).

video


To start with, here is a simple animation showing just one wave pattern; let's call these the major waves. The waves are fairly large, meaning their amplitude is large and so is their length: they take up a sizeable portion of the cloak. The gait of the four cloaks is the 'opposite' pattern, in which the waves of neighbouring cloaks approach one another. The red ball is there only as a reminder where the 0,0,0 point is in this virtual 3D space.

video


The next phase, above, is of course to show the minor waves: there are more of them and they travel faster along the cloak. Mind you, I have not considered the effects of interacting waves on propulsion much yet; my first suspicion is that they can augment one another, but if they can do that, they can probably also hinder one another.  Hm. This will require thought.

video

Anyway, programming and visualising all this makes it difficult to think of everything at once, so first let's see what the combination looks like. Here it is. I like it; it is complex and looks organic and fairly odd. The movement reminds me of that of nudibranchs (if 'nudibranchs' mean nothing to you, just use that word to search for images in Google. You may find that you have to make room next on your book shelf next to the cephalopod section; nudibranchs look delightfully alien too.)

video
   
Very well, let's now assemble a whole cloakfish with this new swimming pattern. The body assemby is modelled very roughly here, without any details at all. As you can see, I wondered whether cloakfish might be able to change colour? I do not see why not, so here is my first attempt ever of depicting a Furahan animal changing colour. For the technically minded, the colour changes require  two steps: first I wrote a simple Matlab program to interpolate colours between two images, resulting in a new set of images showing intermediate changes. Second, I wrote a python script to get Vue Infinite, the programme I use to render the image, to load a different image to use as texture for each frame. In this case the changes in colour are not that big, but you can probably envisage cloakfish changing colours in much more radical fashion.

video


video

Here is the colour change again, first in close-up, and then in the form of a short scene of a common cloakfish making its way over a reef. Those who are very observant will see that the alignment of the body with the cloak-and-dagger assembly differs between the two animations. The reason for that is simply that I forgot to rotate the body around its longitudinal axis by 45 degrees. The reef scene shows the correct position of the body.

Anyway, clearly and obviously, animations have their own attraction and advantages, such as showing colour changes. How can I ever show a cloakfish changing colour on a painting?