Cabral and Leedom suggest line integral convolution to visualize vector fields. The method computes for every pixel a local streamline going through it. For each segment of the streamline lying inside a pixel an integral of a convolution kernel is computed. The integrals are used to compute a weighted sum of all pixels intersected by the local streamline through the initial pixel. The resulting sum gives the output value for the pixel. The authors take for vector field visualization white noise as input values for the pixels.
The above image shows a three-dimensional electrostatic field visualized by volumetric raytracing a scalar field produced by a line integral convolution over white noise.