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.