Merge pull request JuliaPlots#3134 from kellertuer/quiver3

Proposes a 3D quiver

src/examples.jl

@@ -1081,6 +1081,27 @@ const _examples = PlotExample[
             plot!(sin, -π, π, lw=3, color=:red)
         end]
     ),
+    PlotExample(
+        "3d quiver",
+        "",
+        [quote
+            using Plots
+
+            ϕs = range(-π, π, length=50)
+            θs = range(0, π, length=25)
+            θqs = range(1, π-1, length=25)
+
+            x = vec([sin(θ) * cos(ϕ) for (ϕ, θ) in Iterators.product(ϕs, θs)])
+            y = vec([sin(θ) * sin(ϕ) for (ϕ, θ) in Iterators.product(ϕs, θs)])
+            z = vec([cos(θ) for (ϕ, θ) in Iterators.product(ϕs, θs)])
+
+            u = 0.1 * vec([sin(θ) * cos(ϕ) for (ϕ, θ) in Iterators.product(ϕs, θqs)])
+            v = 0.1 * vec([sin(θ) * sin(ϕ) for (ϕ, θ) in Iterators.product(ϕs, θqs)])
+            w = 0.1 * vec([cos(θ) for (ϕ, θ) in Iterators.product(ϕs, θqs)])
+
+            quiver(x,y,z, quiver=(u,v,w))
+        end]
+    ),
 ]
 
 # Some constants for PlotDocs and PlotReferenceImages
@@ -1099,6 +1120,7 @@ _backend_skips = Dict(
         32, # spy
         49, # polar heatmap
         51, # image with custom axes
+        52, # 3d quiver
     ],
 )
 

src/recipes.jl

@@ -1197,35 +1197,51 @@ function quiver_using_arrows(plotattributes::AKW)
     if !isa(plotattributes[:arrow], Arrow)
         plotattributes[:arrow] = arrow()
     end
-
+    is_3d = haskey(plotattributes,:z) && !isnothing(plotattributes[:z])
     velocity = error_zipit(plotattributes[:quiver])
     xorig, yorig = plotattributes[:x], plotattributes[:y]
+    zorig = is_3d ? plotattributes[:z] : []
 
     # for each point, we create an arrow of velocity vi, translated to the x/y coordinates
     x, y = zeros(0), zeros(0)
-    for i = 1:max(length(xorig), length(yorig))
+    is_3d && ( z = zeros(0))
+    for i = 1:max(length(xorig), length(yorig), is_3d ? 0 : length(zorig))
         # get the starting position
         xi = _cycle(xorig, i)
         yi = _cycle(yorig, i)
-
+        zi = is_3d ? _cycle(zorig, i) : 0
         # get the velocity
         vi = _cycle(velocity, i)
-        vx, vy = if istuple(vi)
-            first(vi), last(vi)
-        elseif isscalar(vi)
-            vi, vi
-        elseif isa(vi, Function)
-            vi(xi, yi)
-        else
-            error("unexpected vi type $(typeof(vi)) for quiver: $vi")
+        if is_3d
+            vx, vy, vz = if istuple(vi)
+                vi[1], vi[2], vi[3]
+            elseif isscalar(vi)
+                vi, vi, vi
+            elseif isa(vi, Function)
+                vi(xi, yi, zi)
+            else
+                error("unexpected vi type $(typeof(vi)) for quiver: $vi")
+            end
+        else # 2D quiver
+            vx, vy = if istuple(vi)
+                first(vi), last(vi)
+            elseif isscalar(vi)
+                vi, vi
+            elseif isa(vi, Function)
+                vi(xi, yi)
+            else
+                error("unexpected vi type $(typeof(vi)) for quiver: $vi")
+            end
         end
-
         # add the points
         nanappend!(x, [xi, xi + vx, NaN])
         nanappend!(y, [yi, yi + vy, NaN])
+        is_3d && nanappend!(z, [zi, zi + vz, NaN])
     end
-
     plotattributes[:x], plotattributes[:y] = x, y
+    if is_3d
+        plotattributes[:z] = z
+    end
     # KW[plotattributes]
 end