Default Lighting tweaks

[ffreyer]

Description

Good defaults are quite subjective but since there has been a discussion on slack I thought we could consider tweaking things a bit more before releasing 0.20.

Some constraints:

1. I want to avoid oversaturation, i.e. the bright blob you may see prior to 0.20. This requires the maximum intensity to b capped at (or close to) 1.
2. I want to keep diffuse = 1.0 because it's a nice default value which means that 100% of incoming light is considered in diffuse lighting/reflections
3. I want to keep light_color * diffuse relatively large to keep a good contrast between light and dark regions. That contrast can be quite helpful to see creases and understand curvature.

For now I halfed specular to 0.2 and increase ambient to 0.45.

Intensity

If I simplified things correctly this should give you the intensity as function of angle between the camera/view direction (vector between camera and pixel) and the normal at that pixel.

using LinearAlgebra, GLMakie
function max_intensity(phi; 
        ambient = Makie.MAKIE_DEFAULT_THEME[:ambient][].r,
        light_color = Makie.MAKIE_DEFAULT_THEME[:light_color][].r,
        lightdir = Makie.MAKIE_DEFAULT_THEME[:light_direction][],
        diffuse = 1.0, specular = 0.4
    )
    camdir = Vec3f(0, 0, -1)
    phi_spec = acos(dot(camdir, normalize(lightdir + camdir)))
    return ambient + light_color * (
        max(0.0, cos(phi)) * diffuse + max(0.0, cos(phi - phi_spec)^32) * specular
    )
end

f = Figure()
ax = Axis(f[1, 1], ylabel = "Intensity", xlabel = "angle(normal, camdir)")
lines!(ax, -pi/2 .. pi/2, 
    x -> max_intensity(x, lightdir = Vec3f(0, 0, -1), ambient = 0.55, light_color = 1.0, diffuse = 0.4, specular = 0.2), 
    color = RGBf(0.9, 0.6, 0.6), label = "master")
lines!(ax, -pi/2 .. pi/2, max_intensity, color = :gray, label = "beta-20")
lines!(ax, -pi/2 .. pi/2, x -> max_intensity(x, ambient = 0.45, specular = 0.2), color = :black, label = "specular = 0.2, ambient = 0.45")
axislegend(ax, position = :cb)
hlines!(ax, 1.0, color = :red, linestyle = :dash)
f

Sphere mesh

fig = Figure(size = (800, 450))
Label(fig[1, 1], "specular = 0.4, ambient = 0.35", tellwidth = false)
ax, p = mesh(fig[2, 1], Sphere(Point3f(0), 1f0), color = :white)

Label(fig[1, 2], "specular = 0.2, ambient = 0.45", tellwidth = false)
ax, p = mesh(fig[2, 2], Sphere(Point3f(0), 1f0), color = :white, specular = 0.2)
ax.scene.lights[1].color[] = RGBf(0.45, 0.45, 0.45)

fig

Brain mesh

brain = Makie.FileIO.load(assetpath("brain.stl"))
color = [abs(tri[1][2]) for tri in brain for i in 1:3]

fig = Figure(size = (800, 450))
Label(fig[1, 1], "specular = 0.4, ambient = 0.35", tellwidth = false)
ax, p = mesh(fig[2, 1], brain, color = color, specular = 0.4)
ax.scene.lights[1].color[] = RGBf(0.35, 0.35, 0.35)

Label(fig[1, 2], "specular = 0.2, ambient = 0.45", tellwidth = false)
ax, p = mesh(fig[2, 2], brain, color = color, specular = 0.2)
ax.scene.lights[1].color[] = RGBf(0.45, 0.45, 0.45)

fig

Arrows

pts = fill([0,0,0], 4)
dirs = [[1,0,0], [0.5,0.5,0], [0,0.5,0.5], [-0.5, 0, 0.5]]
color = [:white, :orange, :yellow, :purple]

fig = Figure(size = (800, 450))
Label(fig[1, 1], "specular = 0.4, ambient = 0.35", tellwidth = false)
ax, p = arrows(fig[2, 1], Point3f.(pts), Vec3f.(dirs); color)
update_cam!(ax.scene, Vec3f(2.5, 0.2, 1.3), Vec3f(0.4, 0.3, 0.3))

Label(fig[1, 2], "specular = 0.2, ambient = 0.45", tellwidth = false)
ax, p = arrows(fig[2, 2], Point3f.(pts), Vec3f.(dirs); color, specular = 0.2)
ax.scene.lights[1].color[] = RGBf(0.45, 0.45, 0.45)
update_cam!(ax.scene, Vec3f(2.5, 0.2, 1.3), Vec3f(0.4, 0.3, 0.3))
fig

Type of change

Delete options that do not apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• Added an entry in NEWS.md (for new features and breaking changes)
• Added or changed relevant sections in the documentation
• Added unit tests for new algorithms, conversion methods, etc.
• Added reference image tests for new plotting functions, recipes, visual options, etc.

[MakieBot]

Compile Times benchmark

Note, that these numbers may fluctuate on the CI servers, so take them with a grain of salt. All benchmark results are based on the mean time and negative percent mean faster than the base branch. Note, that GLMakie + WGLMakie run on an emulated GPU, so the runtime benchmark is much slower. Results are from running:

using_time = @ctime using Backend
# Compile time
create_time = @ctime fig = scatter(1:4; color=1:4, colormap=:turbo, markersize=20, visible=true)
display_time = @ctime Makie.colorbuffer(display(fig))
# Runtime
create_time = @benchmark fig = scatter(1:4; color=1:4, colormap=:turbo, markersize=20, visible=true)
display_time = @benchmark Makie.colorbuffer(fig)

	using	create	display	create	display
GLMakie	3.54s (3.47, 3.61) 0.06+-	485.95ms (396.21, 578.21) 76.68+-	688.63ms (671.15, 714.43) 18.14+-	7.88ms (7.69, 8.04) 0.11+-	25.92ms (25.55, 26.31) 0.27+-
master	3.54s (3.43, 3.64) 0.08+-	470.13ms (399.02, 557.25) 70.82+-	698.12ms (665.14, 719.82) 19.02+-	7.85ms (7.67, 8.01) 0.12+-	25.97ms (25.59, 26.28) 0.28+-
evaluation	1.00x invariant, -0.01s (-0.08d, 0.88p, 0.07std)	0.97x invariant, 15.82ms (0.21d, 0.70p, 73.75std)	1.01x invariant, -9.5ms (-0.51d, 0.36p, 18.58std)	1.00x invariant, 0.04ms (0.30d, 0.59p, 0.12std)	1.00x invariant, -0.05ms (-0.17d, 0.76p, 0.27std)
CairoMakie	3.06s (3.04, 3.08) 0.01+-	348.17ms (340.39, 355.80) 5.10+-	154.77ms (149.22, 160.93) 3.74+-	7.83ms (7.68, 8.13) 0.15+-	602.35μs (596.57, 614.51) 6.03+-
master	3.05s (3.01, 3.14) 0.04+-	351.13ms (341.11, 372.38) 11.02+-	155.43ms (148.80, 164.55) 4.92+-	7.83ms (7.64, 7.97) 0.12+-	603.28μs (600.17, 607.52) 2.86+-
evaluation	1.00x invariant, 0.01s (0.42d, 0.46p, 0.03std)	1.01x invariant, -2.95ms (-0.34d, 0.54p, 8.06std)	1.00x invariant, -0.66ms (-0.15d, 0.78p, 4.33std)	1.00x invariant, 0.0ms (0.03d, 0.95p, 0.13std)	1.00x invariant, -0.93μs (-0.20d, 0.72p, 4.45std)
WGLMakie	3.82s (3.77, 3.93) 0.05+-	352.19ms (339.36, 364.21) 11.09+-	9.09s (8.89, 9.40) 0.17+-	10.10ms (9.74, 10.42) 0.24+-	72.83ms (68.69, 82.93) 4.91+-
master	3.77s (3.71, 3.82) 0.04+-	349.23ms (342.60, 356.20) 4.75+-	9.13s (9.05, 9.21) 0.07+-	10.11ms (9.83, 10.36) 0.19+-	72.32ms (68.06, 87.30) 7.12+-
evaluation	0.99x invariant, 0.05s (1.02d, 0.08p, 0.05std)	0.99x invariant, 2.96ms (0.35d, 0.53p, 7.92std)	1.00x invariant, -0.04s (-0.31d, 0.58p, 0.12std)	1.00x invariant, -0.0ms (-0.02d, 0.97p, 0.22std)	0.99x invariant, 0.51ms (0.08d, 0.88p, 6.02std)

[jkrumbiegel]

Looks good, your considerations sound very well thought out