Concepts and coordinate systems

Term	Meaning in WebAR Fácil
Target	Reference image and its precomputed features.
Model-view matrix	Target or anchor transform expressed in camera coordinates.
Projection matrix	Camera intrinsics expressed for the renderer, including the near and far planes.
Anchor	A content transform retained relative to a spatial reference.
Content transform	The model's local position, scale and rotation relative to the tracked parent.

Pose matrices have 16 elements in column-major order. Treat the projection and model-view as a pair and let the wrapper apply the conventions it expects. With a custom renderer, align the projected viewport with the displayed video crop. Apply visual offsets to a child of the tracked group so a new pose can update the parent independently. The optical backend uses relative units until initialized with a metric reference.