Schroeder, Volpe, and Lorensen developed a stream polygon to
visualize tensor information in a vector field.
The stream polygon is a regular n-sided polygon oriented normal to
a local 3D vector in a given point.
The local deformation of the vector field in that point is
computed by a first order Taylor's series expansion
and is given as the sum of a local strain tensor and a
local deformation tensor.
The stream polygon is deformed by either the whole deformation tensor,
just a component of it, or an additional derived tensor (eg. the vorticity
tensor for a velocity field).

The above picture shows a streamtube visualizing the air flow
in a ventilated room.
The streamtube is constructed by computing in every point of
a streamline a streampolygon. The tube is coloured with room pressure
and the radius is varied such that it represents a constant mass flow.
The streamtube is therfore thin in areas of fast flow and thick
where the flow is slow.