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Patella
patella builds a patella mesh from a humanoid's stature and sex.
extensions/humanoid/skeleton/leg/patella/{dimensions,geometry,mass}.mojo. Shared field, isosurface and occupancy code lives under extensions/humanoid/skeleton/.
This is not a three.js port. See Extensions and Femur.
from extensions.humanoid.sex import MALE
from extensions.humanoid.spec import HumanoidSpec
from extensions.humanoid.skeleton.leg.patella.geometry import patella
from units.si import FOOT, Length
var person = HumanoidSpec(Length(6.0, FOOT), MALE)
var bone = patella(person)side picks RIGHT or LEFT. A right patella is the default. detail sets the marching-tetrahedra grid. Twenty-four is the default. Eight is the least. Sixty-four is the most.
The bone stands on y. The origin is the centroid. Plus y is proximal. Plus x is lateral. Plus z is anterior. A left patella is the right shape with x flipped.
The patella has no Trotter and Gleser line. Height, width and thickness are authored sex-specific ratios of stature. They are template parameters. They are not a cited osteometric table.
| Measure | Male ratio of stature | Female ratio of stature | Role |
|---|---|---|---|
| Height, proximal to distal | 0.0253 | 0.0240 | Authored template ratio |
| Width, medial to lateral | 0.0248 | 0.0236 | Authored template ratio |
| Thickness, anterior to posterior | 0.0123 | 0.0118 | Authored template ratio |
A six foot male gets a patella about 46 mm high, 45 mm wide and 22 mm thick on this template.
patella_dimensions(stature, sex, side) returns the sizes and landmarks without building a mesh.
The accepted stature interval is 1.2 m through 2.5 m. That is the software range.
The solid is a triangular sesamoid. A proximal base meets a distal apex. The anterior face is convex. The posterior face holds two articular facets and a vertical ridge. The lateral facet is the larger of the two.
The mesh is a tapered shield with a broad base and a narrow apex. Its posterior ridge separates the facets. The mesh is a marching-tetrahedra isosurface. Connectivity and smooth normals come from the sampled field.
PatellaDimensions is editable. Editing a length does not rebuild landmarks. Call patella_dimensions to resolve a template. Call validate before a field, mesh or mass consumes an edited copy.
PatellaDimensions stores attachment and articular points in meters, as a Vector3 always does.
| Member | Meaning |
|---|---|
apex |
Distal point. |
base |
Proximal border. |
ridge |
Posterior vertical ridge. |
patella_distance(dimensions, point) is the signed distance in meters. Negative is inside.
Tissue data is the same as the femur. See Femur. The patella has no marrow cavity.
The mesh is the outer surface. A thin cortical shell wraps a trabecular interior. patella_mass(spec) samples the field. Each cell is empty, cortical region or trabecular region.
Apparent density already includes porosity. The mass formula applies that factor once.
from extensions.humanoid.skeleton.leg.patella.mass import patella_mass
from units.si import GRAM, NEWTON, POUND_FORCE
var report = patella_mass(person)
report.mass.to(GRAM)
report.weight().to(NEWTON)
report.weight().to(POUND_FORCE)report.solid_tissue is the tissue volume after porosity. report.mass is bone-tissue mass.
The report does not estimate a mineral-component mass.
A six foot male at a 5 mm step has about 28 g of bone tissue. That is 0.27 N, or 0.062 lbf, on Earth. The value is a grid-sampled estimate under the template tissues. It is not a proven upper bound.
Left and right patellas match in mass at the same step, within sampling error.
Stature must lie in 1.2 m through 2.5 m. Sex must be MALE or FEMALE. BodySide must be RIGHT or LEFT. A bare integer is a compile error. Edited zero or non-finite dimensions fail at validate.
examples/patella.mojo draws four patellas in a row and writes out/patella.png. The row is a five foot female, a five foot six female, a six foot male and a six foot six male. Run it with:
.venv/bin/mojo run -I . examples/patella.mojo out/patella.png