datashader fixes for AggMean (#4346)

* store `value` not intermediate aggregator in pixelbuffer * add reference tests * fix bb method for 3d points * add mean example to docs * add changelog * fix and spruce up docs example * Update examples2d.jl * Update examples2d.jl * change interpolate to false by default and add note to docstring --------- Co-authored-by: Simon <[email protected]>
MakieOrg · Oct 15, 2024 · 7cb44c7 · 7cb44c7
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 - Changed image, heatmap and surface picking indices to correctly index the relevant matrix arguments. [#4459](https://github.com/MakieOrg/Makie.jl/pull/4459)
 - Improved performance of `record` by avoiding unnecessary copying in common cases [#4475](https://github.com/MakieOrg/Makie.jl/pull/4475).
+- Fix usage of `AggMean()` and other aggregations operating on 3d data for `datashader` [#4346](https://github.com/MakieOrg/Makie.jl/pull/4346).
 
 ## [0.21.14] - 2024-10-11
 
@@ -49,7 +50,7 @@
 - `plotfunc()` and `func2type()` support functions ending with `!` [#4275](https://github.com/MakieOrg/Makie.jl/pull/4275).
 - Fixed Boundserror in clipped multicolor lines in CairoMakie [#4313](https://github.com/MakieOrg/Makie.jl/pull/4313)
 - Fix float precision based assertions error in GLMakie.volume [#4311](https://github.com/MakieOrg/Makie.jl/pull/4311)
- - Support images with reversed axes [#4338](https://github.com/MakieOrg/Makie.jl/pull/4338)
+- Support images with reversed axes [#4338](https://github.com/MakieOrg/Makie.jl/pull/4338)
 
 ## [0.21.9] - 2024-08-27
 

diff --git a/ReferenceTests/src/tests/examples2d.jl b/ReferenceTests/src/tests/examples2d.jl
@@ -1531,6 +1531,32 @@ end
  f
 end
 
+@reference_test "Datashader AggCount" begin
+ data = [RNG.randn(Point2f, 10_000); (Ref(Point2f(1, 1)) .+ 0.3f0 .* RNG.randn(Point2f, 10_000))]
+ f = Figure()
+ ax = Axis(f[1, 1])
+ datashader!(ax, data; async = false)
+ ax2 = Axis(f[1, 2])
+ datashader!(ax2, data; async = false, binsize = 3)
+ ax3 = Axis(f[2, 1])
+ datashader!(ax3, data; async = false, operation = xs -> log10.(xs .+ 1))
+ ax4 = Axis(f[2, 2])
+ datashader!(ax4, data; async = false, point_transform = -)
+ f
+end
+
+@reference_test "Datashader AggMean" begin
+ with_z(p2) = Point3f(p2..., cos(p2[1]) * sin(p2[2]))
+ data2d = RNG.randn(Point2f, 100_000)
+ data3d = map(with_z, data2d)
+ f = Figure()
+ ax = Axis(f[1, 1])
+ datashader!(ax, data3d; agg = Makie.AggMean(), operation = identity, async = false)
+ ax2 = Axis(f[1, 2])
+ datashader!(ax2, data3d; agg = Makie.AggMean(), operation = identity, async = false, binsize = 3)
+ f
+end
+
 @reference_test "Heatmap Shader" begin
  data = Makie.peaks(10_000)
  data2 = map(data) do x

diff --git a/docs/src/reference/plots/datashader.md b/docs/src/reference/plots/datashader.md
@@ -25,6 +25,23 @@ hidedecorations!(ax); hidespines!(ax)
 fig
 ```
 
+### Mean aggregation
+
+The `AggMean` aggregation type requires `Point3`s where the mean is taken over the z values of all points that fall into the same x/y bin.
+
+```@figure backend=GLMakie
+with_z(p2) = Point3f(p2..., cos(p2[1]) * sin(p2[2]))
+points = randn(Point2f, 100_000)
+points_with_z = map(with_z, points)
+
+f = Figure()
+ax = Axis(f[1, 1], title = "AggMean")
+datashader!(ax, points_with_z, agg = Makie.AggMean(), operation = identity)
+ax2 = Axis(f[1, 2], title = "AggMean binsize = 3")
+datashader!(ax2, points_with_z, agg = Makie.AggMean(), operation = identity, binsize = 3)
+f
+```
+
 ### Strange Attractors
 
 ```@figure backend=GLMakie

diff --git a/src/basic_recipes/datashader.jl b/src/basic_recipes/datashader.jl
@@ -94,10 +94,11 @@ function Canvas(bounds::Rect2; resolution::Tuple{Int,Int}=(800, 800), op=AggCoun
  xsize, ysize = resolution
  n_elements = xsize * ysize
  o0 = null(op)
+ v0 = value(op, o0)
  aggbuffer = fill(o0, n_elements)
- pixelbuffer = fill(o0, n_elements)
+ pixelbuffer = fill(v0, n_elements)
  # using ReshapedArray directly like this is not advised, but as it lives only briefly it should be ok
- return Canvas(Rect2{Float64}(bounds), resolution, op, aggbuffer, pixelbuffer, (o0, o0))
+ return Canvas(Rect2{Float64}(bounds), resolution, op, aggbuffer, pixelbuffer, (v0, v0))
 end
 
 n_threads(::AggSerial) = 1
@@ -116,9 +117,10 @@ end
 function change_op!(canvas::Canvas, op::AggOp)
  op == canvas.op && return false
  o0 = null(op)
+ v0 = value(op, o0)
  if eltype(canvas.aggbuffer) != typeof(o0)
  canvas.aggbuffer = fill(o0, size(c.aggbuffer))
- canvas.pixelbuffer = fill(o0, size(c.pixelbuffer))
+ canvas.pixelbuffer = fill(v0, size(c.pixelbuffer))
  end
  return true
 end
@@ -334,8 +336,11 @@ For best performance, use `method=Makie.AggThreads()` and make sure to start jul
  show_timings = false
  """
  If the resulting image should be displayed interpolated.
+ Note that interpolation can make NaN-adjacent bins also NaN in some backends, for example
+ due to interpolation schemes used in GPU hardware. This can make it look
+ like there are more NaN bins than there actually are.
  """
- interpolate = true
+ interpolate = false
  MakieCore.mixin_generic_plot_attributes()...
  MakieCore.mixin_colormap_attributes()...
 end
@@ -344,13 +349,14 @@ function fast_bb(points, f)
  N = length(points)
  NT = Threads.nthreads()
  slices = ceil(Int, N / NT)
- results = fill(Point2f(0), NT, 2)
+ results = fill(Point2d(0), NT, 2)
+ R = eltype(points) isa Point2 ? Rect2d : Rect3d
  Threads.@threads for i in 1:NT
  start = ((i - 1) * slices + 1)
  stop = min(length(points), i * slices)
- pmin, pmax = extrema(Rect2f(view(points, start:stop)))
- results[i, 1] = f(pmin)
- results[i, 2] = f(pmax)
+ pmin, pmax = extrema(R(view(points, start:stop)))
+ results[i, 1] = f(Point2d(Point3d(pmin)))
+ results[i, 2] = f(Point2d(Point3d(pmax)))
  end
  return Rect3f(Rect2f(vec(results)))
 end