Torso

add_torso attaches the vertebrae, the ribs, the sternum, the shoulder girdle, their joint tissues and the torso's muscles, vessels, nerves, lymphatics and skin.

The torso shares the pelvis frame. The origin is the midpoint of the two hip joint centers. Plus y is proximal, plus x is body-right and plus z is anterior. The package is extensions/humanoid/skeleton/torso/. See Pelvis for the base it stands on.

This is not a three.js port. See Extensions.

A quality level sets how many triangles the body holds. See Mesh quality.

Call it

from extensions.humanoid.sex import MALE
from extensions.humanoid.spec import HumanoidSpec
from extensions.humanoid.skeleton.torso.body import add_body
from extensions.humanoid.skeleton.torso.contents import BOTH, SKIN
from units.si import FOOT, Length

var person = HumanoidSpec(Length(6.0, FOOT), MALE)

add_torso attaches the torso's layers under a parent node. Hang it from the same node as the pelvis. add_body attaches the torso, the pelvis, both legs and feet, both arms and hands, and the neck and the head. It draws one skin from the head down to the wrists, and a skin for each hand. Pass contents to pick the layers. Combine layers with plus.

Value	Draws
BONES	The seventeen vertebrae, twenty-four ribs, the sternum, and the clavicles and scapulae.
LIGAMENTS	The intervertebral discs, the costal cartilages, two spinal ligaments and the shoulder girdle's joints.
MUSCLES	Named torso muscles.
VESSELS	Arteries and veins.
LYMPH	The cisterna chyli, the thoracic duct and two node groups.
NERVES	The spinal cord and the named nerves.
SKIN	Skin envelope.
BOTH	Bones, ligaments and muscles.
ALL	Every named layer.

A bare integer is a compile error. The neck and the head are on their own page; see Head. The thoracic and abdominal organs are not modeled. The arms hang from the shoulder girdle; see Arm.

Size

Every landmark is authored in centimeters on the six-foot male template. Stature scales it. The values are template parameters. They are not a cited osteometric table. A female template is 8% narrower and 5% shallower through the chest.

The column stands on the pelvis's sacral promontory, so it meets the sacrum for either sex. On the six-foot male template, T1 lies about 52 cm above the hip joint centers. The humeral heads lie 18.5 cm to either side of the midline.

Bones

Part	Shape
T1 to T12	Thoracic vertebrae.
L1 to L5	Lumbar vertebrae.
STERNUM	The manubrium, the body and the xiphoid as one plate.
RIB_1 to RIB_12	Paired ribs.
CLAVICLE	Paired. A flat S from the manubrium to the acromion.
SCAPULA	Paired. The blade, the spine and the acromion, the coracoid and the glenoid.

A vertebra is a body, two pedicles and laminae around the canal, a spinous process and two transverse processes. The bodies grow wider and deeper down the column. The column climbs in a lumbar lordosis and a thoracic kyphosis. The thoracic spines slope down steeply in the mid-thorax.

Vertebral bodies use flat endplates at the authored lower and upper y coordinates. Their full body height is the listed height; no rounded sweep cap extends into the disc space. Discs use horizontal elliptical sections between those endplates, including the C7–T1 junction. These template planes enforce a dimensional contract, not measured endplate anatomy. The dens, arches, processes and their smooth joins remain separate features. This change does not certify that all tissues are disjoint or suitable for contact or finite-element analysis.

A rib is a spline through its head, its tubercle, its angle and the side of the chest to its costal cartilage. The ribs fall from back to front. The first rib is short and broad. The eleventh and twelfth ribs float: they end at the side.

The clavicle runs from the manubrium out, up and back to the acromion. Its medial two-thirds bow forward and its lateral third bows back. The scapula lies on the back of the chest from the second rib to the seventh, just lateral of the erector spinae. Its glenoid faces out and a little forward, under the acromion. shoulder_girdle returns the girdle's landmarks. upper_arm_point places a point on the hanging arm.

A thin cortical shell wraps trabecular bone, and the red marrow lives in its pores. torso_bone_mass samples the solid on a grid.

Joint tissues and ligaments

Part	Paired	Role
Intervertebral discs	No	Fibrocartilage between each two bodies, and under L5 on the sacrum.
Costal cartilages	Yes	From the first ten ribs to the sternum and the costal margin.
Anterior longitudinal ligament	No	A wide band down the front of the bodies.
Supraspinous ligament	No	Along the tips of the spinous processes.
Sternoclavicular joint	Yes	The disc and the capsule between the clavicle and the manubrium.
Acromioclavicular joint	Yes	The capsule between the clavicle and the acromion.
Coracoclavicular ligament	Yes	The conoid and the trapezoid, from the coracoid up to the clavicle.

Muscles

Part	Role
Rectus abdominis	A strap from the pelvis's rectus to the fifth to seventh cartilages.
External oblique	The flank from the lower ribs down, and the front toward the rectus.
Internal oblique	The internal oblique and the transversus, drawn as one deep layer.
Erector spinae	From the pelvis's erector up beside the spines to the upper thorax.
Quadratus lumborum	From the crest to the twelfth rib.
Psoas major	From beside the first lumbar bodies down to the pelvis's psoas.
Diaphragm	A dome over the abdomen, with two crura on the lumbar bodies.
Intercostals	The muscles of every intercostal space, drawn as one.
Serratus anterior	Slips from the upper ribs around the chest wall to the scapula's medial border.
Pectoralis major	A thick belly from the sternum, the cartilages and the clavicle to a tendon on the humerus.
Latissimus dorsi	A broad sheet from the spines and the fascia to a tendon that twists under the arm to the humerus.
Trapezius	From the thoracic spines and the base of the neck to the scapular spine, the acromion and the clavicle.
Rhomboids	The minor and the major, from the upper thoracic spines to the scapula's medial border.
Pectoralis minor	From the third to fifth ribs to the coracoid.
Subclavius	Under the clavicle, from the first rib out.

The diaphragm is unpaired; the other fourteen are paired. The trapezius ends at the base of the neck, where the head's upper trapezius goes on. The waist narrows between the rib cage and the crest. The arm's own muscles are on the Arm page.

Vessels, nerves and lymph

The thoracic aorta rises from where the heart would be, arches to the left of the spine and descends. It meets the upper abdominal aorta, which meets the pelvis's aorta. The inferior vena cava climbs right of the spine. The azygos vein runs up the right of the bodies. The internal thoracic arteries run behind the cartilages and continue as the epigastric arteries. Intercostal arteries and veins run under the ribs.

The subclavian artery arches over the first rib and under the clavicle to the armpit. The subclavian vein runs in front of it. There the arm's axillary vessels take them over.

The spinal cord runs down the canal from T1 to its conus at the first lumbar disc. The sympathetic trunks run down the rib heads and the lumbar bodies. The intercostal nerves run under the ribs. The iliohypogastric nerve crosses the back of the abdomen toward the groin. The brachial plexus leaves the spine by T1, crosses the first rib behind the subclavian artery and reaches the armpit.

The cisterna chyli lies in front of the first two lumbar bodies. The thoracic duct carries its lymph up toward the neck. Para-aortic nodes lie beside the lumbar aorta. Parasternal nodes follow the internal thoracic vessels. Axillary nodes lie in the fat of the armpit.

Mass uses the physical radius. The mesh uses a wider display radius for the thinnest branches.

Skin

The torso's skin uses the leg's method. See Integument. The loft runs from below the waist to the base of the neck, and covers the shoulder girdle. It leaves out where the pectoralis major and the latissimus dorsi reach the humerus. The arm's skin covers the folds of the armpit there.

For a male the fat is 14 mm over the abdomen and 8 mm over the chest. For a female it is 24 mm and 15 mm.

A section that stands out from its neighbors puts a kink in the skin. The kink shows as a band of light across the body.

fit_loft can relax the sections after it fills the dips. Each relaxing pass blends a section's reach with its neighbors' reach. The skin can move in by at most half its fat, so no solid comes through. The torso uses eight passes. The pelvis and the arms use four.

A female template has breasts over the pectoralis major. Each breast is an ellipsoid of its own, turned a little out and down, in a smooth union with the loft. A loft section is one closed curve around its center, so it cannot dip between the two breasts.

body_skin_mesh morphs the lower body's skin into the torso's across the waist, from the widest part of the hips up to the waist. The band is about 10 cm tall, so the flank narrows gradually and not in a step. Past the last full section of each loft, that section goes on straight, so the morph never reads a loft's tapered end.

The neck's skin is a column, and the shoulders' is nearly flat on top. A ridge on each side follows the upper trapezius from the side of the neck down to the acromion. It is a tapered capsule in a smooth union with the body, and it slopes the line from the neck to the shoulder.

Each arm's skin joins that surface in a smooth union at the shoulder. The head's skin joins it in a smooth union at the base of the neck. The body then has one surface, from the head down to the wrists. add_body meshes each hand's skin on its own, at its own detail, because a finger is too slim for a grid that spans the body.

Across the wrist the hand's skin turns into the arm's, so the two meshes lie on one surface where they overlap. Past the overlap the hand's skin sinks under the arm's. The body's mesh leaves out the arm's skin past the wrist, where the hand's mesh draws it. So the two skins never cross, and the wrist shows no seam.

Examples

examples/torso.mojo draws a six-foot male body twice and writes out/torso.png. The left copy shows bones, joint tissues and muscles. The right copy shows the skin. The program also prints the mass of several torso parts.

.venv/bin/mojo run -I . examples/torso.mojo out/torso.png