CairoMakie has issues plotting 3D Rects with poly

[ranocha]

The code

julia> using CairoMakie

julia> poly(
               [
                       Rect(0.0, 0, 0, 1, 1, 2.5),
                       Rect(1.0, 0, 0, 1, 1, 1),
                       Rect(0.0, 1, 0, 1, 1, 1),
                       Rect(1.0, 1, 0, 1, 1, 1),
               ],
               color = 1:4
       )

produces the plot

The 3D rectangles are not shown correctly. I would have expected something like I get with a smaller size of the big one:

julia> poly(
               [
                       Rect(0.0, 0, 0, 1, 1, 2.4),
                       Rect(1.0, 0, 0, 1, 1, 1),
                       Rect(0.0, 1, 0, 1, 1, 1),
                       Rect(1.0, 1, 0, 1, 1, 1),
               ],
               color = 1:4
       )

• what version of Makie are you running? (]st -m Makie)

(jl_oQJ1ul) pkg> st -m Makie CairoMakie
  [13f3f980] CairoMakie v0.12.18
  [ee78f7c6] Makie v0.21.18

• can you reproduce the bug with a fresh environment ? (]activate --temp; add Makie)

Yes

• What platform + GPU are you on?

Julia 1.10.7, Apple M2

[ffreyer]

This is more or less expected. We can't do depth sorting per pixel in Cairo, so we do it per triangle using the average z value of the involved vertices. With that it can be the case that a triangle that is partially behind another ends up in front because its mostly closer to the camera/viewer.

You can work around this by making multiple plots and ordering them yourself:

f,a,p = poly(
    Rect(0.0, 0, 0, 1, 1, 2.5),
    color = 1, colorrange = (1, 4)
)
poly!(a,
    [
        Rect(1.0, 0, 0, 1, 1, 1),
        Rect(0.0, 1, 0, 1, 1, 1),
        Rect(1.0, 1, 0, 1, 1, 1),
    ],
    color = 2:4, colorrange = (1, 4)
)
f

(This currently doesn't work on 0.22, see #4738)

[ranocha]

Thanks for the answer