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Dynamics - Forces

Updated: Mar 28, 2022

It would not be an exaggeration to say that forces are the mother of all simulations. It is unthinkable for anything to move without forces in simulations. As there are universal forces like Gravity, Wind, Turbulence affecting all simulations, there are also specific forces that shape simulations like liquid, gas etc.


Gravity : A natural phenomenon by which all things with mass or energy are attracted to (or gravitate toward) one another. The weakest/strongest force that shapes the universe with no distance limit. The propagation speed is considered the speed of light constant. In other words, if we think that the sun's rays reach the earth in 8 minutes, if the sun suddenly disappeared, the earth would continue to orbit for 8 minutes as if the sun were present.


Gravity of Earth is g = 9.80665 m/s2. This value is the calculation of acceleration of a falling object. Based on that, for every second that object falling, 9.80665 meters added to the speed of the object. First second the speed is 9.81m/s, second one is 9.81m/s + 9.81m/s = 19.62m/s, third second : 19.62m/s + 9.81m/s = 29.43m/s... goes on in that fashion. If there is no air resistance, all objects fall to the ground at the same speed.

Variation value can be found in simulations. This represents a kind of fake air resistance.

The gravitational pulls of some celestial bodies are as follows:

Sun: 274 m/sn²

Mercury: 3.7 m/s²

Venus: 8.87 m/s2

Moon: 1.62 m/s2

Mars: 3.711 m/s²

Jupiter: 24.79 m/s

Saturn: 10.44 m/s²

Uranus: 8.69 m/s2

Neptune: 11.15 m/s2


Wind : Just wind. The direction of the wind is given by changing the direction of the wind icon. Strength is the force of wind. Turbulence is the wind blowing at different speeds and directions, clustered at different points. Frequency is the rate of change of turbulence. Scale is the size of the clusters.

Vortex : It rotates the objects in the form of whirlpools, whirlwinds, tornadoes.


Rotation : It rotates objects around a specific axis and center.

Turbulence : Explained in the wind. Think of it like a ripple in a vacuum.

Attractor : It attracts objects towards itself or another object defined.

Drag : It simulates object passing through dense medium like air, water etc., which serves to slow objects down.

Spin : It rotates the objects around their axes at certain speeds and directions. It has a variation value.


Scale : It can enlarge or shrink objects in their centers. It has random parameter.


Path Follow : Makes particles follow a defined path.


Avoid/Deflector : It changes direction of particles to avoid contact with the defined object.


Explode/Bomb : Moves particles to outward with explosion-like velocity.


Keep Apart : Pushes particles to not touch each other. Particle scale, radius will define the distance.


Life : A control operator. It determines the action to be taken when the particles reach a certain age (frame). Particles can be destroyed with kill or can be switched to a new event/action.

Kill : It destroys the particles when certain conditions are met. eg. Bound Box or Life. When particles cross the boundaries of a designated box, they are destroyed. It's important in processing-intensive scenes.


Follow Surface : It allows particles to move over or stick to the surface of an object.


Spawn : When certain conditions are met (specified speed, collision, etc.), it multiplies the particles. That's it for now.


Stay safe.





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