# Use of RegionFunction with Graphics3D?

I'd like to plot in 3D a long list of polygons created with TetGenConvexHull, but only in regions specified by a function. Is that possible? As I have it my RegionFunction only applies to some points, and not to my Graphics3D Polygon data:

Show[{ListPointPlot3D[{{-0.57735, 0., 0.8165}, {-0.866025, -0.5, 0.}},
RegionFunction ->
Function[{x, y, z},z <= .6],
BaseStyle -> {Black, PointSize[Large]}, AxesLabel -> {x,y,z},Boxed -> False,
AxesOrigin -> {0,0,0}, BoxRatios -> {1, 1, 1},
PlotRange -> {{-1, .1}, {-.6, .6}, {-.1, 1}}],
Graphics3D[{Opacity[0.34], EdgeForm[], Red,
Polygon[{{-0.57735, 0., 0.8165}, {0., 0., 0.}, {-0.866025, -0.5, 0.}}]}],
Graphics3D[{Opacity[0.34], EdgeForm[], Blue,
Polygon[{{-0.57735, 0., 0.8165}, {-0.866025, 0.5, 0.}, {0., 0., 0.}}]}]}]


Notice that RegionFunction clips the first datum in ListPointPlot3D ({-0.57735, 0., 0.8165}), but not the Graphics3D Polygon as I would like. I'd like the Polygon surfaces to be clipped/truncated wherever they intersect the RegionFunction (not for the surface to be omitted entirely, given a single intersection location/coordinate).

Perhaps there is a way to transform Polygon data into ListSurfacePlot3D data, which can be utilized with RegionFunction...

Note: I'm actually plotting a lot of complex polygons (not just 2 planes as in the code above), making me want to stick with Polygon and Graphics3D.

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