# How to make a drop-shadow for a Graphics3D lines and curves?

I have a plane a one line parallel to the plane and I want to make a drop-shadow for this line onto the plane. I try Blur but I had have no succes and I did it using Inkscape. But, I like to know the easy solution.

(*x+y+z=2*)
Q = {-1, 1, 5}; P = {0, 0, 2}; normal = {1, 1, -1};
{u, v} = Take[Orthogonalize@HodgeDual[normal], 2];
st = Graphics3D[{
First@ParametricPlot3D[P + t u + s v, {t, -1, 2}, {s, -3, 2.5},
Mesh -> None, PlotStyle -> {Opacity[0.4], Gray}],
First@ParametricPlot3D[Q - t (u + v), {t, -2, 1},
PlotStyle -> {AbsoluteThickness[4], Orange,
}, Boxed -> False, ViewPoint -> {0.97, 0.27, -3.2},
ViewVertical -> {0.69, 0.7, -0.2}, ImageSize -> 400]


It is not easy for me to get such result in 3D. So I turn to 2D and use DropShadowing which introduce in 13.1 version.
Graphics[{{Opacity[.2], Parallelogram[{0, 0}, {{20, -4}, {5, 8}}]},

• in 3D, only get Graphics3D[{First@ ParametricPlot3D[P + t u + s v, {t, -1, 2}, {s, -3, 2.5}, Mesh -> None, PlotStyle -> {Opacity[0.4], Gray}], First@ParametricPlot3D[{P - t (u + v), Q - t (u + v)}, {t, -2, 1}, PlotStyle -> {Gray, {AbsoluteThickness[4], Orange, Arrowheads[0.06]}}] /. Line -> Arrow}, Boxed -> False, ViewPoint -> {0.97, 0.27, -3.2}, ViewVertical -> {0.69, 0.7, -0.2}, ImageSize -> 400] Commented Sep 13, 2022 at 14:41