If people are curious about why smoke simulations can take a while to create in 3D for
#SpaceX #Starship, here is a detailed thread, which explains the reasons behind my smoke simulations:
Hopefully, people will now understand, of, what it takes to create those smoke plumes.
Starship - VFX/CGI Ground smoke plumes:
Creating smoke plumes digitally is one of the most complex things in VFX (VisualFX).
Having different forces interacting with each other makes things really hard to simulate and to predict how they will behave. Using Houdini as the main simulation package, I will go deep into explaining how different forces interact with each other and how different settings influence those forces.
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Chapter 1 – The emission source:
In real life, when rocket engines start to fire, the exhaust hits the water that is being injected before the ignition process. When those hot gases come into contact with the water, they turn into steam. In 3D, we usually refer to this as smoke.
To start with the emission source, I add a simple sphere, which acts as the emission object for a particle system. This particle system is later used to drive the main smoke simulation on top of it. Simulating the real physical conversion from hot exhaust gases into white steam plumes during launch through water would be a very complex undertaking.
Because of this, the process is simplified by using a basic emission object that emits particles. The particle system is given collision properties and several forces, such as turbulence, roughness (noise), and adjustable force amplitudes.
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Chapter 2 – Driving the smoke simulation:
Once the main particle system is established, it is used to create the smoke simulation. Before this can be done, the particles need additional attributes, such as a density attribute. This density attribute is fed into a smoke solver in Houdini, which is able to emit smoke based on the particle data.
The smoke solver acts as the main brain of the simulation. This is where all smoke-related forces are calculated and combined. Having the correct attributes in place is essential for the smoke simulation to function properly and to produce usable results.
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Chapter 3 – Smoke forces:
This is the most complex, but also the most interesting, part of the simulation process.
The solver used for this setup contains many different forces, each with multiple sub-levels of settings. This makes the entire workflow very demanding and sensitive to small changes.
The forces involved include:
Wind, which pushes the fluid in a specified direction and simulates air currents.
Buoyancy, which causes hotter and less dense fluid to rise while cooler and denser fluid sinks.
Drag, which resists the motion of the fluid and adds a sense of air resistance.
Disturbance 1, which introduces large-scale, gentle, random variations in the flow.
Disturbance 2, which adds medium-frequency breakup and more noticeable variation.
Disturbance 3, which creates small-scale, high-frequency noise for fine surface detail.
Turbulence 1, which generates large rolling or boiling motions.
Turbulence 2, which introduces medium-sized swirling eddies.
Turbulence 3, which creates small, sharp vortices and energetic motion.
Confinement, which sharpens and preserves existing fluid details against natural diffusion.
Each of these forces has its own set of sub-settings that can be adjusted independently. Many of them include ramps and a parameter called the input range.