add naive depth sorting for scatter & text

GLMakie/src/drawing_primitives.jl

@@ -571,6 +571,7 @@ function draw_atomic(screen::Screen, scene::Scene,
         gl_attributes[:uv_offset_width] = uv_offset_width
         gl_attributes[:distancefield] = get_texture!(atlas)
         gl_attributes[:visible] = plot.visible
+        gl_attributes[:depthsorting] = get(plot, :depthsorting, false)
         cam = scene.camera
         # gl_attributes[:preprojection] = Observable(Mat4f(I))
         gl_attributes[:preprojection] = lift(plot, space, markerspace, cam.projectionview, cam.resolution) do s, ms, pv, res

GLMakie/src/glshaders/particles.jl

@@ -176,6 +176,20 @@ function draw_scatter(screen, (marker, position), data)
     rot = vec2quaternion(rot)
     delete!(data, :rotation)
 
+    if to_value(pop!(data, :depthsorting, false))
+        data[:indices] = map(
+            data[:projectionview], data[:preprojection], data[:model],
+            position
+        ) do pv, pp, m, pos
+            T = pv * pp * m
+            depth_vals = map(pos) do p
+                p4d = T * to_ndim(Point4f, to_ndim(Point3f, p, 0f0), 1f0)
+                p4d[3] / p4d[4]
+            end
+            UInt32.(sortperm(depth_vals, rev = true) .- 1)
+        end |> indexbuffer
+    end
+
     @gen_defaults! data begin
         shape       = Cint(0)
         position    = position => GLBuffer
@@ -194,6 +208,7 @@ function draw_scatter(screen, (marker, position), data)
             return shape
         end
     end
+
     @gen_defaults! data begin
         quad_offset     = Vec2f(0) => GLBuffer
         intensity       = nothing => GLBuffer
@@ -226,6 +241,7 @@ function draw_scatter(screen, (marker, position), data)
         scale_primitive = true
         gl_primitive = GL_POINTS
     end
+
     # Exception for intensity, to make it possible to handle intensity with a
     # different length compared to position. Intensities will be interpolated in that case
     data[:intensity] = intensity_convert(intensity, position)