# Fixed arrow size in parametric 3d plot

I'm trying to add arrows to a trajectory in ParametrcPlot3D

    ParametricPlot3D[{Cos[t], Cos[t] Sin[t], t}, {t, 0, 10},
BoxRatios -> {1, 1, 1}, PlotRange -> All] /.
Line[x_] :> {Arrowheads[{0, 0.04, 0.04, 0.04, 0.04, 0}], Arrow[x]}


The arrow that I obtain change with the 3d view. the closer ones look larger and the further ones look small. how can I have the size of the arrow fixed for all 3d views?

Update: It is important that the size of the arrow can be controlled, i.e, the symbolic presentation of Tiny toLarge are not sufficient. ## 2 Answers

You could use a custom glyph, like this:

Manipulate[
h = Graphics[Triangle[{{0, -0.3}, {a, 0}, {0, 0.3}}]];
ParametricPlot3D[{Cos[t], Cos[t] Sin[t], t}, {t, 0, 10},
BoxRatios -> {1, 1, 1}, PlotRange -> All] /.
Line[x_] :> {Arrowheads[{0, {size, Automatic, h}, {size, Automatic,
h}, {size, Automatic, h}, {size, Automatic, h}, 0},
Appearance -> "Projected"], Arrow[x]}, {{size, 6}, 4,
20}, {{a, 1}, 0.1, 3}] • As far as I can tell, you are doing essentially the same thing that I suggested, that is, using sizes that are much larger than 1. – Carl Woll Aug 27 '18 at 21:37
• I just added an option to increase the length of the arrow (triangles) – M.R. Aug 27 '18 at 22:49
• @M.R, when the image is rotated, the size of the arrows change. – jarhead Aug 31 '18 at 12:07

You can use one of the symbolic sizes to create arrowheads that have a fixed size:

ParametricPlot3D[
{Cos[t],Cos[t] Sin[t],t},
{t,0,10},
BoxRatios->{1,1,1},
PlotRange->All
] /. Line[x_] :> {Arrowheads[{0,Large,Large,Large,Large,0}], Arrow[x]} Addendum

I don't know of any documented method to generated fixed arrow head sizes other than using the symbolic values Tiny, Small, etc. However, it seems that using a size greater than 10 or so will generate an arrow head with a fixed size, presumably in pixels. So:

ParametricPlot3D[
{Cos[t],Cos[t] Sin[t],t},
{t, 0, 10},
BoxRatios->{1, 1, 1},
PlotRange->All
] /. Line[x_] :> {Arrowheads[{0,40,40,40,40,0}],Arrow[x]} • Can you make them fixed in a size that is much larger then the symbolic size Large? – jarhead Aug 24 '18 at 13:47
• @jarhead See update – Carl Woll Aug 24 '18 at 18:56
• thanks for the update and the effort, but this way around does not solve the problem yet. In other plots your suggestions, Arrow size Large/40, appear extremely too small/large. – jarhead Aug 26 '18 at 7:06
• I've updated the question – jarhead Aug 26 '18 at 8:16
• @jarhead An example plot where my suggestions don't help would be useful. – Carl Woll Aug 26 '18 at 15:27