Here we see the submarine on a journey through the bloodstream of a human host. Suspended in the watery plasma are myriad red blood cells, carrying oxygen from the lungs to other parts of the body, and a few of the bigger white blood cells. Guardians of the body, the white cells move independently by extending pseudopods, seeking out and attacking any foreign substances. One is chasing the submarine and almost has a grip on the wing fin, but deft work by the pilot should see another group of tourists safely home.
The submarine is a CSG object made entirely of superellipsoids, with other shapes subtracted to make the viewport and portholes. These are filled with a thin screen of yellowish glass, and some interior lights provide the window glow. The paintwork is a simple colour_map (I didn't have time to do an image_map!) and layered over it is a bozo map to represent dirt or other stains.
The red blood cells are fairly simple blobs, with sphere components spun along a sinusoidal circle. The centre is filled with a flat sphere, and two spheres are subtracted to make the dimples. The cells are created by a macro call, which I looped with random numbers for the placement, adjusting until it looked right and there were no object intersections.
The white blood cells are semi-random blobs made of a number of unevenly scaled spheres. The translucent texture allows you to see some more solid blobs inside which represent the cellular nucleus and other components. I gave the white cells a refractive index only slightly higher than 1, to simulate an index a little higher than the plasma in which they are floating. This way I didn't have to give the whole interior of the background blob a refractive index.
The entire scene is, however, filled with a weakly scattering medium, to show the spotlight beam and provide the ambience of being inside a liquid. I always seem to make scenes that require lots of media, which seems to push the render time up by a factor of 5 to 10. :-(
There are only five light sources in this scene: The spotlight, two
lights inside the submarine to provide the glowing windows, and two
shadowless fill lights, which were dimmed down to make the whole scene
gloomy like you'd expect inside a human body.