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Deprecate ObjAdapter's copy of the mesh inertia integral; SymbolicAWEModels owns it #325

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Deprecate ObjAdapter's copy of the mesh inertia integral; SymbolicAWEModels owns it #325

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75746df
Delete the inertia functions ObjAdapter duplicated from SymbolicAWEMo…
1-Bort-1 Sep 16, 2026
d914aed
Merge origin/main: keep both Unreleased Changed entries
1-Bort-1 Sep 16, 2026
e344c8e
Deprecate the ObjAdapter inertia functions instead of deleting them
1-Bort-1 Sep 16, 2026
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8 changes: 8 additions & 0 deletions CHANGELOG.md
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@@ -1,5 +1,13 @@
# Changelog

## Unreleased

### Changed

- BREAKING: `ObjAdapter` no longer exports `center_to_com!`, `calculate_inertia_tensor`

@1-Bart-1 1-Bart-1 Sep 16, 2026

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Keep the functions, mark them deprecated, and rm them in the next breaking release, because otherwise we have too many breaking changes.

@1-Bort-1 1-Bort-1 Sep 16, 2026

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Done in e344c8e: the three functions are back with their export, tests and docs, each emits a deprecation warning, and the changelog entry is a deprecation instead of BREAKING.

or `calc_inertia_y_rotation`; they are gone. Mesh mass properties are computed by
SymbolicAWEModels, which reads the mesh with `read_faces`.

## VortexStepMethod v5.1.1 2026-09-12

### Fixed
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2 changes: 0 additions & 2 deletions docs/src/private_functions.md
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Expand Up @@ -244,8 +244,6 @@ densify_contour
create_interpolations
find_circle_center_and_radius
march_edges
calculate_inertia_tensor
center_to_com!
airfoils_from_yaml
write_geometry_yaml
resolve_aero_geometry
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2 changes: 1 addition & 1 deletion src/obj_adapter/ObjAdapter.jl
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Expand Up @@ -45,7 +45,7 @@ function plot_slices_3d end
export obj_to_yaml, resolve_aero_geometry
export write_geometry_yaml, write_yaml, airfoils_from_yaml
export perpendicular_sections
export read_faces, center_to_com!, calculate_inertia_tensor, calc_inertia_y_rotation
export read_faces
export plot_airfoil_fit, plot_airfoils, plot_slices_3d

end
144 changes: 0 additions & 144 deletions src/obj_adapter/obj_geometry.jl
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Expand Up @@ -226,147 +226,3 @@ function create_interpolations(vertices, circle_center_z, radius, gamma_tip, R=I

return (le_interp, te_interp, area_interp)
end

"""
center_to_com!(vertices, faces)

Calculate center of mass of a mesh and translate vertices so that COM is at origin.

# Arguments
- `vertices`: Vector of 3D point coordinates
- `faces`: Vector of vertex indices for each face (can be triangular or non-triangular)

# Returns
- Vector representing the original center of mass before translation

# Notes
- Non-triangular faces are automatically triangulated into triangles
- Assumes uniform surface density
"""
function center_to_com!(vertices, faces; prn=true)
area_total = 0.0
com = zeros(3)

for face in faces
if length(face) == 3
# Triangle case
v1 = vertices[face[1]]
v2 = vertices[face[2]]
v3 = vertices[face[3]]

# Calculate triangle area and centroid
normal = cross(v2 - v1, v3 - v1)
area = norm(normal) / 2
centroid = (v1 + v2 + v3) / 3

area_total += area
com -= area * centroid
else
throw(ArgumentError("Triangulate faces in a CAD program first"))
end
end

com = com / area_total
!(abs(com[2]) < 0.01) && throw(ArgumentError("Center of mass $com of .obj file has to lie on the xz-plane."))
prn && @info "Centering vertices of .obj file to the center of mass: $com"
com[2] = 0.0
for v in vertices
v .+= com
end
return com
end

"""
calculate_inertia_tensor(vertices, faces, mass, com)

Calculate the inertia tensor for a triangulated surface mesh, assuming a thin shell with uniform
surface density.

# Arguments
- `vertices`: Vector of 3D point coordinates representing mesh vertices
- `faces`: Vector of triangle indices, each defining a face of the mesh
- `mass`: Total mass of the shell in kg
- `com`: Center of mass coordinates [x,y,z]

# Method
Uses the thin shell approximation where:
1. Mass is distributed uniformly over the surface area
2. Each triangle contributes to the inertia based on its area and position
3. For each triangle vertex p, contribution to diagonal terms is: area * (sum(p²) - p_i²)
4. For off-diagonal terms: area * (-`p_i` * `p_j`)
5. Final tensor is scaled by mass/(3*total_area) to get correct units

# Returns
- 3×3 matrix representing the inertia tensor in kg⋅m²
"""
function calculate_inertia_tensor(vertices, faces, mass, com)
# Initialize inertia tensor
I = zeros(3, 3)
total_area = 0.0

for face in faces
v1 = vertices[face[1]] .- com
v2 = vertices[face[2]] .- com
v3 = vertices[face[3]] .- com

# Calculate triangle area
normal = cross(v2 - v1, v3 - v1)
area = norm(normal) / 2
total_area += area

# Calculate contribution to inertia tensor
for i in 1:3
for j in 1:3
# Vertices relative to center of mass
points = [v1, v2, v3]

# Calculate contribution to inertia tensor
for p in points
if i == j
# Diagonal terms
I[i,i] += area * (sum(p.^2) - p[i]^2)
else
# Off-diagonal terms
I[i,j] -= area * (p[i] * p[j])
end
end
end
end
end

# Scale by mass/total_area to get actual inertia tensor
return (mass / total_area) * I / 3
end

function calc_inertia_y_rotation(I_b_tensor)
# Function for nonlinear solver - off-diagonal element should be zero
function eq!(F, theta, _)
# Rotation matrix around y-axis
R_y = [
cos(theta[1]) 0 sin(theta[1]);
0 1 0;
-sin(theta[1]) 0 cos(theta[1])
]
# Transform inertia tensor
I_rotated = R_y * I_b_tensor * R_y'
# We want the off-diagonal xz elements to be zero
F[1] = I_rotated[1,3]
end

theta0 = [0.0]
prob = NonlinearProblem(eq!, theta0, nothing)
sol = NonlinearSolve.solve(prob, NewtonRaphson())
theta_opt = sol.u[1]

R_b_p = [
cos(theta_opt) 0 sin(theta_opt);
0 1 0;
-sin(theta_opt) 0 cos(theta_opt)
]
# Calculate diagonalized inertia tensor
I_diag = R_b_p * I_b_tensor * R_b_p'
@assert isapprox(I_diag[1,3], 0.0, atol=1e-5)
return I_diag, R_b_p
end


2 changes: 0 additions & 2 deletions test/Project.toml
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Expand Up @@ -14,7 +14,6 @@ Logging = "56ddb016-857b-54e1-b83d-db4d58db5568"
MakieControlPlots = "6d616b69-6563-4f6e-8472-6f6c706c6f74"
Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
Serialization = "9e88b42a-f829-5b0c-bbe9-9e923198166b"
StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
Statistics = "10745b16-79ce-11e8-11f9-7d13ad32a3b2"
Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
Expand All @@ -36,7 +35,6 @@ LinearAlgebra = "1"
Logging = "1"
MakieControlPlots = "0.1.5"
Random = "1.10.0"
Serialization = "1"
StaticArrays = "1"
Statistics = "1"
Test = "1"
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5 changes: 0 additions & 5 deletions test/obj_adapter/test_obj_adapter.jl
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Expand Up @@ -113,11 +113,6 @@ obj_path = normpath(joinpath(@__DIR__, "..", "..",
tables) == ""
end

@testset "center_to_com! rejects non-triangular faces" begin
verts = [[0.0, 0.0, 0.0], [1.0, 0.0, 0.0], [0.0, 1.0, 0.0], [1.0, 1.0, 0.0]]
@test_throws ArgumentError center_to_com!(verts, [[1, 2, 3, 4]]; prn=false)
end

@testset "write_yaml emits nested and scalar values" begin
dir = mktempdir()
nested = joinpath(dir, "nested.yaml")
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61 changes: 2 additions & 59 deletions test/ram_geometry/test_kite_geometry.jl
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Expand Up @@ -4,10 +4,9 @@ using VortexStepMethod
using VortexStepMethod: read_aero_matrix
using VortexStepMethod.AirfoilAero: write_aero_matrix
using VortexStepMethod.ObjAdapter: create_interpolations, find_circle_center_and_radius,
calculate_inertia_tensor, center_to_com!, read_faces, calc_inertia_y_rotation
read_faces
using LinearAlgebra
using Interpolations
using Serialization

@testset "Kite Geometry Tests" begin
work_dir = mktempdir()
Expand All @@ -34,30 +33,6 @@ using Serialization
@test faces[1] == [1, 2, 3]
end

@testset "Center of Mass Calculation" begin
vertices = [[0.0, 0.0, 0.0], [1.0, 0.0, 0.0], [0.0, 0.0, 1.0]]
faces = [[1, 2, 3]]

com = center_to_com!(vertices, faces)
expected_com = [-1/3, 0.0, -1/3]

@test isapprox(com, expected_com, rtol=1e-5)
end

@testset "Inertia Tensor Calculation" begin
vertices = [[0.0, 0.0, 0.0], [1.0, 0.0, 0.0], [0.0, 1.0, 0.0]]
faces = [[1, 2, 3]]
mass = 1.0
com = [1/3, 1/3, 0.0]

I = calculate_inertia_tensor(vertices, faces, mass, com)

# Test properties of inertia tensor
@test size(I) == (3,3)
@test isapprox(I, I', rtol=1e-10) # Symmetric
@test all(diag(I) .≥ 0) # Non-negative diagonal
end

@testset "Circle Fitting" begin
# Create simple curved wing vertices
r = 5.0
Expand Down Expand Up @@ -120,17 +95,6 @@ using Serialization
write_aero_matrix(cd_polar_path, cd_matrix, deg2rad.(alphas), deg2rad.(d_trailing_edge_angles), "C_d")
write_aero_matrix(cm_polar_path, cm_matrix, deg2rad.(alphas), deg2rad.(d_trailing_edge_angles), "C_m")

# Create and serialize obj file
faces = [[i, i+1, i+2] for i in 1:3:length(vertices)-2]
open(test_obj_path, "w") do io
for v in vertices
println(io, "v $(v[1]) $(v[2]) $(v[3])")
end
for f in faces
println(io, "f $(f[1]) $(f[2]) $(f[3])")
end
end

# Test reading back the matrices
cl_read, alphas_read, deltas_read = read_aero_matrix(cl_polar_path)
# write_aero_matrix stores coefficients rounded to 4 decimals
Expand All @@ -139,34 +103,13 @@ using Serialization
@test alphas_read ≈ deg2rad.(alphas)
@test deltas_read ≈ deg2rad.(d_trailing_edge_angles)

# Create info file
info_path = test_obj_path[1:end-4] * "_info.bin"
le_interp, te_interp, area_interp = create_interpolations(vertices, z_center, r, π/4, I(3))
center_of_mass = center_to_com!(vertices, faces)
inertia_tensor = calculate_inertia_tensor(vertices, faces, 1.0, zeros(3))

serialize(info_path, (inertia_tensor, center_of_mass, I(3), r, π/4,
le_interp, te_interp, area_interp))


# Test interpolation at middle point
@test isapprox([le_interp[i](0.0) for i in 1:3], [0.0, 0.0, r+z_center], atol=0.03)
@test isapprox([te_interp[i](0.0) for i in 1:3], [1.0, 0.0, r+z_center], atol=0.03)
end

@testset "Alignment to principal frame" begin
vertices, faces = read_faces(test_obj_path)
center_of_mass = center_to_com!(vertices, faces)
inertia_tensor_b = calculate_inertia_tensor(vertices, faces, 1.0, zeros(3))
inertia_tensor_p, R_b_p = calc_inertia_y_rotation(inertia_tensor_b)
for v in vertices
v .= R_b_p * v
end
inertia_tensor_b2 = calculate_inertia_tensor(vertices, faces, 1.0, zeros(3))
inertia_tensor_p2, R_b_p2 = calc_inertia_y_rotation(inertia_tensor_b2)
@test inertia_tensor_p ≈ inertia_tensor_p2
@test R_b_p2 ≈ I(3)
end

@testset "Converted-wing construction and deformation" begin
# TODO: redesign. These previously tested ObjWing internals (radius,
# gamma_tip, UNCHANGED distribution, obj deform\!) that were dropped when
Expand Down
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