Quantum Visualization in Houdini
Kate...How is this relevant to VFX?
Quantum Physics along side AI, are arguably two of the most important emerging technologies of the previous decades. I've talked before of how AI is impacting the film industry. (You can find these articles HERE, and HERE) In summary, AI is already being integrated into VFX roles, and it is a huge factor in how movies are created and marketed. On a side note, go check out Serjan Burlak's work. HERE His work is a great example of how different aspects of science can be integrated into Houdini.
So how could the world of Quantum Physics be applied, and useful to our industry in VFX? Or does it even matter? In this article I'll try to answer both of those questions. I will also break down and explain the study of Quantum Physics as well. I like to think that visual effects artists are the scientists of the post-production world. So I hope you are ready to learn some applied physics.
First an apology to Scott Lang. Yes, I do indeed place the word quantum before everything.
What is Quantum Physics?
Every object in the universe operates according to quantum physics. Quantum physics describes matter and energy as quantum wave-functions. The result of these functions sometimes operate like waves, and sometimes act like particles. The word "quantum" comes from the Latin word for "how much". Considering that quantum physics deals with discrete amounts of matter, this is a pretty good name.
When dealing with the quantum field, the data is always measured in integers. Frequency and wavelengths of light are also important in this field as the measurement of it's energy can be calculated from these factors. Light with a low frequency and long wavelength generates less energy, and emits cooler colors. While light with a higher frequency and shorter wavelength emits hotter tones. Light is a particle that moves as a wave. As such, the study of it is one of the founding concepts of quantum physics.
This field can also be a bit confusing. Quantum physics deals with sets of probabilities. Therefore, it is impossible to predict with certainty of an outcome of a single experiment on a quantum system. Part of the process of studying this field is finding the possibilities for every single outcome of an experiment. Then taking the results and comparing them with the theory and the experiment to generate the most likely answer.
Before we move on, it's probably good if we talk about the theory of Entanglement and Einstein. Albert Einstein one of history's smartest people, and greatest developers of the scientific field. He is recognized with creating the theory of relativity(which is an incredibly important factor in quantum mechanics), the mass–energy equivalence formula, countless contributions to theoretical physics, and founding the original statements for entanglement.
Entanglement describes the relationship between two systems that correlate with each other, even though they exist in different locations. For example, the movement of a particle that exists in your coffee mug could be related to another particle in outer space. However,Einstein calculated that you would need to know the common factors of each particle for this to work. The entanglement system would also rely on these particles communicating faster than the speed of light. Which around Einstein's time was highly theoretical and was considered wrong. In the late 1960's a physicist named John Bell revisited entanglement, and proved that quantum mechanics predicts correlations between distant systems. This finalized the idea that the results of quantum physics is non-local, and that measurements made at one location are dependent on another.
This is probably the most important cat in the history of the world. It's also the backbone theory of quantum mechanics. Ethically, this experiment is going to sound very wrong to people have never heard it before. But please keep in mind that this cat in the box scenario is a thought experiment.
The system goes something like this. A cat is placed in a sealed box with a container of radioactive substance. As this substance breaks down it can trigger a hammer inside the box to break open a vile of acid. Which would kill the cat. As we cannot directly observe the cat, the acid, or any of the other substances inside the box, the cat can be considered both alive and dead at the same time.
This cat state is a paradox situation that explains how entanglement and quantum superposition works. (We'll cover superposition a bit later.) It has been observed and achieved with photons. As well as achieved with trapping beryllium ions in a superposed state.
Particles and Their Characteristics
Before we dive too deeply, I thought it might be good to go over some particles that are studied in quantum physics, and their properties.
Electrons: Electrons are the subatomic particles that orbit the nucleus of an atom. They contain a negative charge, and are smaller than the size of the atom they orbit around.
Ions: An ion is a charged atom or molecule. When an atom is attracted to another atom because it has an unequal number of electrons and protons, the atom is called an ion. If the atom has more electrons than protons, it is a negative ion,which is called an anion. If it has more protons than electrons , the atoms is a positive ion.
Protons: Protons are positively charged subatomic particles found within atomic nuclei.
Atoms: Atoms are the basic units of matter. They are made up of three different particles. Protons, neutrons and electrons. The word atom comes from the Greek word for indivisible. This is because it was once thought that atoms were the smallest particles in the universe.
Kaons: These particles are made up of quarks. Quarks that make up Kaons can be strange (or anti-strange) quarks, or up or down quarks. Kaons that contain a charge are called Mesons.
Photons: A photon is a particle that has waves of electromagnetic radiation. Photons are just electric fields traveling through space. They has no resting mass, charge, or state. But they travel at the speed of light.
Muons: This is a subatomic particle. This particle is similar to an electron but it is 207 times as heavy. It has two forms. One has a negative charge and one has a positive charge. It was discovered in 1936 by physicists Carl D. Anderson and Seth Neddermeyer.
Neutrons: This subatomic particle contains no electric charge, and is one of two particles that make up the nuclei of atoms. It has the mass of one atomic unit. Because it exists inside of an atom, it can also be referred to as a nucleon.
Quarks: Quarks are one of the fundamental components of matter. They help build neutrons, protons, and electrons. Different groups of quarks are called flavors. There are currently six of them known in existence. The six quark flavors can then be placed in three groups. Up and down, charm and strange, and top and bottom.
Neutrinos: Neutrinos are one of the most abundant particles in the universe. They have a very small mass, and have no charge. But they are very hard to detect through nuclear and physical studies. This is because nuclear forces treat electrons and neutrinos identically. So you can sometimes confuse the two while observing them.
Bosons: Bosons are a special type of particle as there is no limit to the number that can occupy the same quantum state. They also help form the element helium-4. Their force is build into them as a spinning motion. Bosons carry forces, and are considered one of the few particles to form the current founding states of matter. The other two being fermions, quarks, and electrons.
Leptons: Leptons are composed of particles that exist on their own. The word lepton comes from the Greek word leptos. Which translates to small. There are six different types of leptons. These contain electrons, the muons, and tau particles. The rest of the categories contain neutrinos of these particles.
The Differences and Definitions Between Quantum Studies
Now that we are through the basics of Quantum Physics, let's talk about the subcategories of this science, and their definitions. Rather than having this article be 300 pages long, I thought it might be better just to break down the categories and studies into a respectful summary. Here are a few groups that scientists of the quantum theory study.
Quantum Mechanics: This is a theory in physics describing the properties of the world on an atomic or subatomic scale. This is different than regular physics or mechanics as classical physics only describes movements and functions on a macroscopic or ordinary scale of measurement. Quantum mechanics also runs on the idea that all energy and momentum can be measured from finite values. These values are called Quantization.
Quantum Computing: This process is used to create computers that run on particles than ones and zeros. It operates the computer based on the actions of particles, rather than a binary code. Since particles can be in multiple places at once, they have the ability to use superposition to orient their existence where ever they need to travel. We can't see where these particles are traveling, as once we have viewed the particle it will not be in the same place as it was. These particles can also take on both the values of one and zero at the same time. This process would not only make regular computers faster, but also help us develop technology.
Quantum Materials: This is a term used to describe any material that has a strong electronic correlation. So pretty much any substance that has superconducting state or property. For example, MRIs, Hard Disk Drives, and biosensors all contain quantum materials to make them work.
Quantum Field Theory: Quantum Field Theory is a framework of theories that is used to construct models of subatomic particles. It combines classical field theory, special relativity, and quantum mechanics to study particle movements.
Quantum Electrodynamics: This science is studied under quantum field theory. It describes the interaction between light and matter particles and their electrodynamics.As well how these interactions take place over space and time. This theory combines the mathematics between quantum mechanics and special relativity.
Scattering Theory: This is a theory for studying and understanding the scattering of waves and particles. This describes how particles from an object react and collided with that of another. For example, sunlight traveling through water or glass. Under the scattering theory there are a few sub-categories. Bragg Scattering is one. This describes the diffraction of electrons from X-rays as they lose or gain energy from colliding with metal foil.
Quantum Chemistry: This field is also called molecular quantum mechanics. This study focuses on the application and development of quantum mechanics between chemical systems. Technologies that have been developed from this field have been vast. For example, infra-red tools, nuclear research tools such as nuclear magnetic resonance spectroscopy, and microscopy devices.
Quantum Electrochemistry: This is a fusion between electrodynamics, quantum mechanics, and electrochemistry. It was first founded as a theory in the early 1960s. This process describes how protons transfer in reactions while in chemical systems.
Direct Quantum Chemistry: This theory measures the motion of the nuclei and the electrons on the same time scales. Which is different than other fields of quantum study that study these two particles on different timescales. These measurements are used calculate motion from high-speed atomic collisions.
Condensed Matter Physics: Condensed-matter physics is the study of substances in their solid state. This study overviews the macroscopic and microscopic physical properties of materials or objects. It creates an understanding of the electromagnetic forces between atoms. It also takes into account the temperature and different magnetic fields of the particles.
Now there are a ton of categories of Quantum Theory. But I do not have room in this article to write them all down. So let's move on to the concepts that are applied while working in this field. These are mathematical formulas that are used to describe the movement of particles,waves, motions, and numbers that exist in this science. You could use these systems in Houdini to create point movement patterns.
Definitions and Examples of Quantum Theory in Action
Macroscale Quantum Effects: While a quantum effect is an effect that is not properly predicted by classical physics. A macro-scale quantum effect is something a bit different. Quantum effects describe the movement of matter particles acting like waves. Macro-scale quantum effects describe particles moving in non-random waves. Particles that move in non-random waves contain more coherence in their form as their particles are aligned.
Free Particle: This is a particle not bound by external forces, and moves according to it's surrounding space. It has a fixed velocity, and it's momentum is created by differences between it's mass and velocity.
Particle In a Box: This model is also called the infinite potential well. It is used to describe the differences between classical and quantum physics. It is a model of a situation where a particle is trapped in a box, but is free to move wherever it would like inside the container. It can contain any position, energy level,or velocity inside the box. It can never be still, and will move from place to place based on how it interacts with the box, what it's energy levels are, and it's velocity. It's outcomes will be different if it's situation is applied to classical or quantum physics. If you are using quantum quantum physics to describe the particle, the particle will only contain positive energy levels. By only having positive energy, the particle will only move to certain areas of the box, or will be detected at certain states. The same goes with negativity energy levels.
Quantum Harmonic Oscillators: A regular harmonic oscillator is a function that describes how curves fluctuate around their origin or equilibrium. Picture a sin curve repeating forever on a graph. The sin curve is repeating the same movement while trying to return to the center of the axis. This would be called an oscillation. The force this curve has while pushing itself away from the equilibrium is called inertia. The force bringing it back down is called elasticity or restoring force. A quantum harmonic oscillator applies the same knowledge, but can calculate these curves in a finite amount of space, one-dimension, or calculate it with discrete energy values.
Solution of Schrödinger Equation For a Step Potential: This is also called a Heaviside step function. Step potential describes how matter waves are reflected and transmitted. By adding Schrodinger's Equation to this function, we can calculate the waves of free particles and their Planck–Einstein relation. This relation states that the energy of a photon is proportional to its frequency.
Josephson Voltage Standard: This concept revolves around the Josephson effect. The Josephson effect sets a standard for voltage using frequency references of particles. It is applied to superconducting circuit chips to generate stable voltages across superconductors. This technique is used to measure and set voltage standards around the world.
Quantum Dots: These are the Nano-particles of semiconductors. They are considered a quantum material. They are made of nano-scale crystals, and these crystals are designed to transport electrons. They can emit colors. Depending on the size and the combination of particles , the crystals can also create artificial molecules.
Cubic Harmonic: This called a Real Function. Real functions are equations that assigns values to arguments. For example y = b(x). Cubic harmonics measure the symmetry of the orbits surrounding atoms.
Quantum Numbers: These can be characterized as conserved values in a dynamic simulation of a quantum system. Or they are also described as : sets of numerical values which give acceptable solutions to the Schrödinger wave equation. The values of these numbers contain known quantities that you can factor into your equations.
Quantum Superposition: Plain superposition is defined as adding two physical states together to form another physical state of matter. Quantum superposition is related, except it refers to the solution to the Schrödinger equation. The result of quantum superposition is a state of matter that is the sum of various other forms of matter. Not just two.
Vacuum State: This quantum state contains the lowest possible energy. It has no particles, but contains electromagnetic waves and particles that pop in and out of existence.
How do Quantum Scientists Traditionally Visualize Particles?
Scientists mostly use 2D representations of the waves and fields of what they observe. This is because it is not only cheaper to create a 2D model on one plane, it also can be a more accurate portrayal based on the experiment.
If a scientist was exploring the particle in a box theory as discussed above, it would be easier to visualize the particle's path as a line. As well as mapping the particle back and forth across those lines. In a 2D plane this could be as simple as showing a moving dot on a line, with four other lines around it forming the box. By deconstructing this experiment to a 2D visualization it helps the viewer easily understand what is happening in the experiment. However, if you were to visualize this movement in a 3D space, the viewer might see the particle's lines overlap, and the box could quickly become a mess of overlying web of paths.
Yet, 3D environments are being used to visualize energy fields of atoms, quantum superposition, and much more. By creating a 3D version of energy fields or particles, the scientist has the ability to view the interactions from different moments in space.
I was unable to find the exact software that they use to visualize these experiments. But CERN has open source database software on the their site that they regularly use in their research. One being Inventio. This software has multiple functions regarding research data management, and digital assets management.
More recently, a paper was released promoting the use of Houdini for Astrophysical Visualization. Astrophysics and Quantum Physics are linked very heavily. As they both deal with measuring spectrums of light, atomic interactions, and particle movements in the vacuum of space. This article was published in April of 2017. Since then, NASA has started to use it in their simulation work.
Would Houdini Help The Field of Quantum Physics?
For most of this section, I will be referencing the Houdini for Astrophysical Visualization study. Simply because they have formulated an amazing system for importing datasets and using the software accordingly. (You can find it HERE)
NASA and other bodies starting to use Houdini, is a perfect example of how flexible and powerful the software is. As quantum physics can be a difficult process for anyone to understand. It is important to create a visual representation of it in the most simplest way. Houdini has this advantage. As long as it can read any incoming data set format, it can assign any of the values with it's library of attributes. J. P. Naiman, Kalina Borkiewicz, and A. J. Christensen, the researchers of the astrophysical visualization study, have already created tutorials and downloadable example data sets and scripts to use in the software. Considering that one of the creators of Houdini was the designer of the simulations for the Canadarm, it is fitting for the software to have come full circle and helped in scientific exploration.
Houdini is also perfect for representing manipulating particles within a volume or finite space. Jumping back to our particle in a box experiment, Houdini could help simplify this particle behavior while also combining experimental factors. The collision system in Houdini has default physical settings for the user to adjust the temperature, dynamic friction, and bounce. This would be perfect for adjusting the collision factors of the box. For the particles, Houdini has a simple POP network that can generate particles from anything. It also has a default interface to adjust the particle's temperature, friction, and bounce. Inside this POP network you can also add wind factors, or adjust the particle's speed through substeps, timescale, or advecting it through volumes. All of these changes can be done under a few minutes.
Houdini contains line and trail SOPs that you could use to generate a trailing path from the moving particles, and create original path of the first particle. The CHOP network could also help to visualize the frequency of the particles if they generate sin, cos, or tan waves throughout the scene.
In an interesting twist of events, quantum physics has already already helped the world of VFX. When Marvel was creating the second Ant-Man movie, their head visual effects supervisor Stephane Ceretti had a background in quantum mechanics. This allowed him to create a realistic abstract representation of the quantum realm. He once again helped create the phasing motion of the villain Ghost. Knowing that a particle can be in multiple places at the same time, he was able to give the effect a proper backstory and representation. Method Studios was also a huge factor in this movie's development. They referenced macro and cellular level photography and played with different ways to visualize quantum mechanics. Without this effort, the effects probably wouldn't be as memorable.
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