message: Clarify densityScale
diff: @@ -763,12 +763,12 @@ concurrently). To create a volume instance, call
  -------------------- ----------------------- ---------- --------------------------------------
  OSPTransferFunction transferFunction [transfer function] to use
  - float densityScale 1.0 used to make volumes uniformly thinner
  - or thicker ([path tracer] only)
  + float densityScale 1.0 makes volumes uniformly thinner or
  + thicker
  float anisotropy 0.0 anisotropy of the (Henyey-Greenstein)
  - phase function in [-1, 1]. Default:
  - Isotropic scattering. ([path tracer] only)
  + phase function in [-1, 1] ([path tracer]
  + only), default to isotropic scattering
  -------------------- ------------------------ --------- ---------------------------------------
  : Parameters understood by VolumetricModel.
  