Category Archives: Concepts

How Your Blender Works

Will it Blend? Not unless it utilizes several Physics concepts.

The actual pitcher of the blender works as a cavitation chamber. Cavitation is the rapid formation and collapse of air cavities in a fluid. Such cavities are formed by rapid changes in pressure, which is where the blade comes into play. In addition to breaking down food into smaller chunks, the blade also rapidly bombards the mixture with small air bubbles that, when they pop, cause shock waves to further break up the food.

This concept is not exclusive to blenders. Mantis shrimps use a variant form of inertial cavitation to propel themselves in the water. For many devices, such as boat propellers, cavitation is undesirable. This ‘accidental’ cavitation usually causes an increase in noise, vibrations, and significant damage to the propeller itself.

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Fluid Dynamics

Becoming increasingly popular, Fluid Dynamics allow for the accurate simulation of water and fluid in animation and video games.  The most common method of achieving sufficient simulation is the application of Navier-Stokes equations. For such an implementation, the software must provide geometry configurations, which the engine uses to simulate the motion of fluid through time.

An alternate method would be to utilize the Smoothed-Particle Hydrodynamics, a system created by Gingold and Monaghan, initially intended for astrophysics.

Collision Detection

Collision detection is necessary for simulating an accurate physics environment. Examples of common usage include prevention of objects from falling through a platform, prevention of objects from passing through each other, and prevention of anything passing outside of boundaries.

To accomplish collision detection without a sophisticated engine, games and software can utilize plane canvases with either an (x,y) or an (x,y,z) coordinate system, whether the game is two-dimensional or three-dimensional, respectively. Thus all objects have a cubic region with coordinates at every corner. So whenever the object moves, the program checks that the object’s region doesn’t intersect any other region, and if it does, then the program moves the object to the nearest sufficient open space.

For more sophisticated collision detection, object velocity, direction, acceleration, and mass must be taken into effect to be able to calculate where the object will move to after colliding, how fast it will move after, and which direction it would move in.

Gravity

Gravity is a vital portion of 3D video games and simulations, as the environment cannot mimic real physics without gravity. Without gravity, characters and objects will not be able to properly move, jump, or fall, because gravity is an essential piece of many motion equations. In most situations, a complete Physics Engine is optimal, as it factors in gravity along with other components – collision detection, rotation calculations, rigid body dynamics, Brownian motion, et cetera), however it is not required. Algorithms for gravity have been written and open sourced for many languages and can be easily found on services like GitHub, Google Code, and SourceForge.

The Force of Gravity equals 9.8 m/s2, so if a character starts falling from rest, his speed will increase according to the time elapsed squared times the force of gravity. The speed can then be used to calculate how much damage must be applied to the character, so falling for one second doesn’t hurt the player as much as falling for 4 seconds, which adds an additional dynamic to gameplay.