Simulating Sharks

Chomp, Chomp, Chomp….

Currently, there are around 520 species of shark. Sharks also fit into a group of animals called cartilaginous fishes. There are over 1200 species of these fish. They not only include sharks, but also skates, rays, and chimaeras. They are fish that have structures of cartilage in their bodies.

Sharks have existed for millennia.There are many existing fossil records of sharks from prehistoric times, and from well over 400 million years.

There isn’t too much data for how long sharks live for, but their age range varies per range of species. Sharks like the Smooth Dogfish only live for 16 years, Porbeagle Sharks live for 46 years, and Whale Sharks can live for over 100 years. The world's longest living shark is the Greenland Shark. It can live for over 400 years.

They can also be found in almost any ocean.

Some species of sharks also don’t need to swim constantly in order to keep breathing. Some sharks such as the nurse shark have spiracles that force water across their gills automatically. So they never need to stop moving. Sharks don’t need sleep like we do, instead they have active and restful periods.

They lack eyelids, so their eyes remain open always. Different species have been observed hanging in open water with their mouths open. It is thought that this is their restful period.

Sharks also have an excellent sense of hearing. Their ears are located inside of their head, and on both sides. They can hear frequencies under 1,000 hertz, which most aquatic creatures can be heard under. This helps the creature locate prey and splashing sounds in water.

The size of the animals also varies per species. Sharks can be as small as a human hand to over 12 metres long. The larger the shark, the larger the prey it will feed on. Some feed on plankton, while others feed on fish and squids.

Sharks play a critical part in the world's ecosystem. As predators they keep all over species in the ocean under control. They prevent overpopulation in fish, while doing so they impact all parts of the ecosystem.

Shark Facts

Shark Studies

Sharks are very ancient creatures. So many studies on them are focused on their ancestors. So let’s talk about dinosaurs.

One ancient shark scientists are looking at is the 300 million year old “Godzilla Shark”. This shark was discovered in 2013. Palaeontologists were able to verify this species existence after finding a 6.7foot long fossilised skeleton in the Manzano Mountains near Albuquerque, New Mexico. The jaws of the creature included 12 rows of teeth and 2.5 foot long spines on its back.

It was given the nickname godzilla shark after its massive size, and is now formally called Hoffman's dragon shark (Dracopristis hoffmanorum). This species of shark fits into a group of sharks called Ctenacanths. These creatures diverged from the branch of sharks we know today around 390 million years ago. Ctenacanths have much more rigid jaws, which are less flexible than regular sharks. This makes them less efficient predators and more bottom feeders in their environment.

Their teeth were also more adapted to crushing and grasping prey than tearing them to shreds. Their spines are thought to be used as defence against larger sharks.

Another large dinosaur shark is the megalodon. You might have heard of this famous shark. But they existed around 23 million years ago. Their newborns are slightly larger than human adults (2 metres), and the full grown size of them is around 14 metres.

A hypothesis of why these sharks grew so big is that they are thought to consume their siblings in the womb. This behaviour has been seen in modern sharks, and helps make sure the babies have enough nutrients before they are born.

Little is known about the shark's biology, but the little of what we do know is about its skeleton. Its skeleton was mainly made up of cartilage, which is why so few fossilised remains exist of it. Cartilage is very hard to preserve over time, and isn't as dense or solid as bones.

Lately, scientists have been studying the shark’s vertebrae. Unlike the rest of their body, the backbones of the shark can harden over time due to calcium salts. Which in turn fossilize the cartilage. The vertebrae of the shark are also a great way for scientists to map the age of the shark as they are similar to trees.In the sense where they have annual growth bands.

In order to find these bands, researchers used an imaging technique calle micro-computed tomography. These images showcased 46 growth bands in the vertebrae they scanned. Which means the said shark lived for about 46 years.

Jumping back into the modern era, there are a few efforts to preserve and monitor the species of shark we have left. Global populations of sharks have declined over the past 50 years. So keeping them off of the endangered list of species has become very important. Environment factors are playing a huge role in their demise, as well as rising ocean temperatures.

Satellite remote sensing(SRS) is playing a huge role in tracking the behaviour of sharks, as well as their populations. They allow for a huge area of ocean to be monitored, as well as options to track specific groups of sharks. Additionally, it allows for certain environmental factors to be tracked over time, and how the long term effects of the environment might affect the ecosystem over time.

This is a promising technology, and there are a lot of different avenues to explore with SRS.

Shark Simulations

Now onto simulating sharks….There are a few awesome scientific examples of shark simulations out there, so let's take a look at them.

There have been a few visualisations in the fast couple of years that have focused on the skin of sharks. Certain sharks have something called denticile development that takes part across their body. These denticles are teeth like protrusions across the shark's skin. After studying them for a bit, scientists noticed something super interesting about them.

The denticles seemed to follow a turing-like pattern across the sharks. This means their distribution follows a reaction-diffusion system. This pattern has also been seen in other vertebrates to help create their feathers, scales,teeth, and skin textures. This trait confirms that most vertebrates have shared ancestors between them. In sharks, it is still not confirmed what these denticles are used for. In other species this reaction-diffusion pattern is used to create drag reduction, thermoregulation, and communication.

Alan Turing patterns are responsible for most of nature's diversity. It is also responsible for limb growth in animal tissue.

You can check out this study here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6221541/

Models of sharks are also starting to be used in classrooms to better explain natural selection to students. Particularly with hammerhead sharks. In a classroom it's often hard to explain a theory straight off the bat. So any diagrams that you can use, can help create a better understanding of the material.

These hammerhead models and simulations were created by Georgia Southern University, and they are designed for easy manipulation of variables, and custom factors. Using these simulations students can see in realtime evolutionary outcomes for changing environmental factors. The simulation also allows for students to control the cephalofoil of the shark. This allows for the aerodynamics of the shark to change, and in turn how the surrounding water currents might affect it.

There are also a few dynamic models of lemon sharks out there on the internet. Vertebrates, such as sharks that live for long periods of time, are often affected by environmental pollution.This in turn affects their ageing. In order to make sure these creatures live long successful lives, we need to combat how pollutants spread throughout the water, and create successful treatments for them.

A group of scientists completed a 17 year study in a coastal nursery in Bimini, Bahamas to help build these models of lemon sharks. Lemon sharks are traditionally very hard to study, as finding older adults can be difficult. They used a Markov-chain stochastic model to start tracking the traits of these animals. This study was able to showcase that pollution is leading to shorter lifespans of these sharks, delayed breeding times, causing randomised population fluctuations.

Shark Simulations in Houdini and in VFX

So in VFX, sharks are animated and simulated quite frequently. A lot of effort goes into simulating the water around them as well as their textures and animation. When I landed my first role as an fx artist, the studio I worked at had just wrapped on this film called The Meg. From what the staff around me told me, simulating massive amounts of water sequences was painful, and required a huge amount of farm space. So their stories scared me away from water simulation for a long time, but also made me a bit curious on how the shark elements were layered around them.

There are a few amazing UK studios that really dig in deep when it comes to simulating sharks. Outpost VFX being one of them. For a film called 47 metres down, they worked on over 420 shots which involved both 2D and 3D effects work. They used a combination of live action plates with CG sharks, and full CG environments.

Their techniques were quite impressive as they had around 40 artists working on the film, and were the only VFX vendor on it. So creating the close up sequences, shark attacks, and deep sea shots was a big undertaking. They mainly used Houdini for the fluid and particle simulations, sculpted the sharks in Zbrush, and animated in Maya.

In Houdini, there are a lot of references out there of sharks leaping out of the water, and fluid and whitewater being created around them. However, there aren't many examples of shark skin, shark behaviour, or accurate swimming patterns.

However, I did find a really great example of them in Andrew Lowell’s fxphd || fxguide course. Andrew has this amazing course regarding fuzzy logic and particle behaviour in Houdini, which you can check out here: https://www.youtube.com/watch?v=i8DBCWRze74

In this course Andrew uses fuzzy logic and particles to create shark swarms. Using feedback systems and vector maths, he was able to create some very realistic looking swarms. I highly recommend checking it out.