The Black-and-White Effect

Black-and-white video displays the luminance of each pixel.

function main()
  ctexture2d(colorTexture, fragmentTexCoord).rgb
  ddot(c, vec3(0.213, 0.715, 0.072))
  gl_FragColorvec4(d, d, d, 1.0)

Luminance models the human eye's response to various wavelengths of light. Green is most prominent, red is less so, and blue is least prominent. The values used here are standard for HDTV.