Graphics3D opacity of lines

Question

I would like to make the lines opaque for a plot of form similar to:

Graphics3D[{Opacity[0.1], Line[RandomVariate[
    MultinormalDistribution[{0, 0, 0}, {{1, 0, 0}, {0, 1, 0}, {0, 0, 1}}], 1000]]}]

Using opacity here doesn't seem to produce a similar effect to using an equivalent for a 2d ListPlot, where it is easier to see the layering.

ListLinePlot[
 RandomVariate[MultinormalDistribution[{0, 0}, {{1, 0}, {0, 1}}], 
 1000], PlotStyle -> {Opacity[0.4], Black}]

Does anyone know how I can recreate this similar type of effect with the 3D plot of a line?

Answer 1

This also works for me in 10.1.0 under Windows 7 x64. Take a look at your rendering settings; referencing Graphics3D: Opacity limitations this is affected by DepthPeelingLayers for example.

plot = Graphics3D[{Opacity[0.1], 
    Line[RandomVariate[
      MultinormalDistribution[{0, 0, 0}, {{1, 0, 0}, {0, 1, 0}, {0, 0, 1}}], 1000]]}];

Table[
   Show[plot, BaseStyle -> RenderingOptions -> {"DepthPeelingLayers" -> n}],
   {n, {1, 5, 10, 20, 40, 80}}
] ~Partition~ 3 // Grid

Perhaps your rendering hardware simply doesn't support this method, or perhaps "Software" rendering is being used. Try specifically:

Table[
  Show[plot, BaseStyle -> RenderingOptions ->
   {"Graphics3DRenderingEngine" -> method}],
 {method, {"HardwareDepthPeeling", "BSPTree", "Software"}}
]

Note that on my system "Software" produces a result not too dissimilar to the one you are experiencing.