Concepts Geometries and Visuals

This concepts page combines geometry and visual setup:

defining geometry directly on a Physics3D.System
giving each geometry a local_transform
creating matching visuals and understanding the difference

Geometry and visual side by side

Geometry and visuals can both be added to a Physics3D.System. In this concepts page:

geometry is the simulation shape (used for physical interaction)
visual is the rendered shape (used for what you see)

SimpleScene is Physics3D.System:
    pillar_geometry is Physics3D.Geometries.Cylinder:
        local_transform.position: Math.Vec3.from_xyz(0.0, 0.0, 0.5)
        radius: 0.15
        height: 1.0
    pillar_visual is Visuals.Geometries.Cylinder:
        local_transform.position: Math.Vec3.from_xyz(0.0, 0.0, 0.5)
        radius: 0.15
        height: 1.0

The two objects are complementary:

change pillar_geometry to affect simulation behavior
change pillar_visual to affect rendering appearance

Organizing geometry and visual variants for reuse

Define base system models and specialize dimensions and transforms in child models.

BaseMarkerScene is Physics3D.System:
    marker_geometry is Physics3D.Geometries.Cylinder:
        local_transform.position: Math.Vec3.from_xyz(0.0, 0.0, 1.0)
        radius: 0.2
        height: 0.3
    marker_visual is Visuals.Geometries.Cylinder:
        local_transform.position: marker_geometry.local_transform.position
        radius: marker_geometry.radius
        height: marker_geometry.height

SmallMarkerScene is BaseMarkerScene:
    marker_geometry.radius: 0.1
    marker_geometry.height: 0.2

LargeMarkerScene is BaseMarkerScene:
    marker_geometry.radius: 0.4
    marker_geometry.height: 0.8

Here marker_visual reads its dimensions and position from marker_geometry, so variants only update one source of truth.

Preparing for later interaction logic

Even before introducing rigid bodies, you can structure the scene so geometry/visual pairs are easy to reference later.

AssemblyLayout is Physics3D.System:
    axle_geometry is Physics3D.Geometries.Cylinder:
        local_transform:
            position: Math.Vec3.from_xyz(0.0, 0.0, 0.2)
            rotation: Math.Quat.from_euler_angles(0.0, Math.Functions.deg_to_rad(90.0), 0.0)
        radius: 0.05
        height: 1.0
    axle_visual is Visuals.Geometries.Cylinder:
        local_transform.position: axle_geometry.local_transform.position
        local_transform.rotation: axle_geometry.local_transform.rotation
        radius: axle_geometry.radius
        height: axle_geometry.height

Recommended naming pattern:

<name>_geometry for simulation shape
<name>_visual for rendered counterpart

That makes later concepts pages on rigid bodies, mates, and signals easier to follow.