BlindGiRl

The world is not uniform as we all know. Atoms combine in molecules to produce the wide variety of materials we know. Waves can travel through all materials – often the material a wave is travelling through is called media.

Waves travel differently through 'glass' walls

However, as they travel through different media waves exhibit different properties. For example the speed of sound in the air is 343 meters per second and in water it is 1484 meters per second.

Waves tend to attenuate with distance. That happens because the wave looses energy. The amount of attenuation depends on the media they travel through.

Attenuation and “speed” are the two main properties that describe the environments in BlindGiRl wave simulation.

Read more about the speed of sound and attenuation at Wikipedia.

In order to simulate the real world physics properties of waves at 60 frames per second for the whole world of BlindGiRl, we use the Xbox 360 graphics processor (GPU) parallel power. This technique, when calculations not directly related to graphics are performed on the GPU, is often referred to as “General Purpose computation on Graphics Processing Units” or GPGPU.

A GPU has the ability to process a lot of similar information in parallel using little programs called shaders. Most of the time shaders are used to render computer generated images on screen. However, people realised that there are a lot of calculations that could take advantage of that kind of power – including physics simulations about waves and a little girl.

You can read more about GPUs and GPGPUs at Wikipedia.

In a previous post we talked about how BlindGiRl runs a realistic simulation of wave behaviour. As BlindGiRl moves around the world she creates noise – represented as red waves. These red waves increase in amplitude and frequency as BlindGiRl runs faster i.e. the steps become respectively louder and more frequent.

The Doppler Effect in evidence

However you may notice that the waves are a lot closer together in the direction of movement of BlindGiRl and a lot more spaced in the opposite direction. This is called a “Doppler Effect”, and is the result of a change in the frequency of the waves due to the motion of the source (BlindGiRl herself)

If you’re interested in the physics of waves, read more about the Doppler Effect, amplitude, and frequency at Wikipedia.

BlindGiRl uses a simplified fluid simulation to simulate sound wave propagation. Every frame, at each point in the environment, such simulation is being executed. This allows for the waves to behave in a realistic, real-world manner. Wave physics phenomena like reflection, refraction, and interference, can be observed all the time in BlindGiRl – they happen because that’s how waves behave.

You can find out more about the different types of waves via Wikipedia, and ripple tanks (which the levels in BlindGiRl are a roughly similar to),  here.

BlindGiRl features complex wave simulations