What the code does
This demo loads a picture of rabbits included in the PTB distribution, conversts it to a texture and dynamically fades the texture in and out of visibility with a temporal sine wave function. It does this by changing the "alpha" value of the texture (this is called alpha blending, or compositing). The alpha value ranges between 0-1, 0 being completely invisible and 1 being completely visible. For a value of 0.5 you can see half of the image and half of the background colour (the alpha value of the texture oscillates around this value during the demo).
