message: updated the doc for the tone mapper
diff: @@ -1859,10 +1859,10 @@ To set a pixel operation to the given framebuffer use
  #### Tone Mapper
  The tone mapper is a pixel operation which implements a generic filmic tone
  -mapping operator. It approximates the Academy Color Encoding System (ACES)
  -by default. The tone mapper is created by passing the type string "`tonemapper`"
  -to `ospNewPixelOp`. The tone mapping curve can be customized using the
  -parameters listed in the table below.
  +mapping operator. Using the default parameters it approximates the Academy
  +Color Encoding System (ACES). The tone mapper is created by passing the type
  +string "`tonemapper`" to `ospNewPixelOp`. The tone mapping curve can be
  +customized using the parameters listed in the table below.
  ----- ---------- -------- -----------------------------------------
  Type Name Default Description
  @@ -1885,6 +1885,20 @@ parameters listed in the table below.
  ----- --------- -------- -----------------------------------------
  : Parameters accepted by the tone mapper.
  +To use the popular "Uncharted 2" filmic tone mapping curve instead, set the
  +parameters to the values listed in the table below.
  +
  + Name Value
  + --------- --------
  + contrast 1.1759
  + shoulder 0.9746
  + midIn 0.18
  + midOut 0.18
  + hdrMax 6.3704
  + acesColor false
  + --------- --------
  + : Filmic tone mapping curve parameters. Note that the curve includes an
  + exposure bias to match 18% middle gray.
  Rendering
  ---------
  