Remove reflections from surface plots?

[fvmarcoline]

Hello. Is there a way to turn off reflections on surface plots? In the following example, the colors are modified near the surface extrema and saddle points due to, presumably, reflections from a light source.

using Plots
x = -2π:0.02:2π;
z = sin.(x) .* sin.(x)';
ticks = (-2π:π:2π, ["-2π";"-π";"0";"π";"2π"]);
plot(surface(x, x, z, camera=(0,90), aspect_ratio=:equal, xlims=extrema(x), ylims=extrema(x), ymirror=:true, zticks=[], zlims=(-2,2), clims=(-2,2), framestyle=:box, xticks=ticks, yticks=ticks,left_margin=8mm,right_margin=0mm,xlabel="surface()"),
            heatmap(x, x, z, aspect_ratio=:equal,xlims=extrema(x),ylims=extrema(x),clims=(-2,2),zlims=(-2,2), framestyle=:box, xticks=ticks, yticks=ticks,xlabel="heatmap()",left_margin=-5mm),size=(800,360),layout=@layout [a{0.53w} b])

While heatmap() does not have these surface reflections, in practice, I am using surface() because my x and y inputs are generally not regular, and heatmap, to my knowledge, requires a regular grid. Thanks!