mirror of
https://gitlab.com/MisterBiggs/stl-process.git
synced 2025-08-03 12:01:33 +00:00
76 lines
2.6 KiB
Julia
76 lines
2.6 KiB
Julia
using MeshIO
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using FileIO
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using LinearAlgebra
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stl = load(raw"C:\Users\albig\Downloads\cubeblender.stl")
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# stl = load(raw"C:\Coding\stl_read\3DBenchy.stl")
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function get_mass_properties(triangles)
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"""
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Reference:
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https://github.com/WoLpH/numpy-stl/blob/42b6c67324e13b8712af6730f77e5e9544ef63b0/stl/base.py#L362
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https://www.geometrictools.com/Documentation/PolyhedralMassProperties.pdf
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"""
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x = reduce(hcat, [[v[1] for v in tri] for tri in triangles])'
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y = reduce(hcat, [[v[2] for v in tri] for tri in triangles])'
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z = reduce(hcat, [[v[3] for v in tri] for tri in triangles])'
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function subexpression(x)
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w0, w1, w2 = x[:, 1], x[:, 2], x[:, 3]
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temp0 = w0 + w1
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f1 = temp0 + w2
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temp1 = w0 .* w0
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temp2 = temp1 .+ w1 .* temp0
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f2 = temp2 .+ w2 .* f1
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f3 = w0 .* temp1 .+ w1 .* temp2 .+ w2 .* f2
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g0 = f2 .+ w0 .* (f1 .+ w0)
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g1 = f2 .+ w1 .* (f1 .+ w1)
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g2 = f2 .+ w2 .* (f1 .+ w2)
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return f1, f2, f3, g0, g1, g2
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end
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x0, x1, x2 = x[:, 1], x[:, 2], x[:, 3]
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y0, y1, y2 = y[:, 1], y[:, 2], y[:, 3]
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z0, z1, z2 = z[:, 1], z[:, 2], z[:, 3]
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a1, b1, c1 = x1 - x0, y1 - y0, z1 - z0
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a2, b2, c2 = x2 - x0, y2 - y0, z2 - z0
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d0, d1, d2 = b1 .* c2 .- b2 .* c1, a2 .* c1 .- a1 .* c2, a1 .* b2 .- a2 .* b1
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f1x, f2x, f3x, g0x, g1x, g2x = subexpression(x)
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f1y, f2y, f3y, g0y, g1y, g2y = subexpression(y)
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f1z, f2z, f3z, g0z, g1z, g2z = subexpression(z)
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intg = zeros(10)
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intg[1] = sum(d0 .* f1x)
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intg[2:4] = [sum(d0 .* f2x), sum(d1 .* f2y), sum(d2 .* f2z)]
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intg[5:7] = [sum(d0 .* f3x), sum(d1 .* f3y), sum(d2 .* f3z)]
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intg[8] = sum(d0 .* (y0 .* g0x + y1 .* g1x + y2 .* g2x))
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intg[9] = sum(d1 .* (z0 .* g0y + z1 .* g1y + z2 .* g2y))
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intg[10] = sum(d2 .* (x0 .* g0z + x1 .* g1z + x2 .* g2z))
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intg = intg ./ [6, 24, 24, 24, 60, 60, 60, 120, 120, 120]
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volume = intg[1]
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center_of_gravity = intg[2:4] / volume
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cogsq = center_of_gravity .^ 2
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inertia = zeros((3, 3))
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inertia[1, 1] = intg[6] + intg[7] - volume .* (cogsq[2] + cogsq[3])
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inertia[2, 2] = intg[5] + intg[7] - volume .* (cogsq[3] + cogsq[1])
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inertia[3, 3] = intg[5] + intg[6] - volume .* (cogsq[1] + cogsq[2])
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inertia[1, 2] = inertia[2, 1] = -(intg[8] - volume .* center_of_gravity[1] .* center_of_gravity[2])
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inertia[2, 3] = inertia[3, 2] = -(intg[9] - volume .* center_of_gravity[2] .* center_of_gravity[3])
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inertia[1, 3] = inertia[3, 1] = -(intg[10] - volume .* center_of_gravity[3] .* center_of_gravity[1])
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return volume, center_of_gravity, inertia
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end
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v, cog, inertia = get_mass_properties(stl)
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v
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cog
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inertia
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eigen(inertia)
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