8 Objects that depend on other objects🔗ℹ

Some objects should follow others. A label may follow a moving point. An altitude may depend on the vertices of a triangle. A background box may need the measured size of its text.

A relation-visual declares such a dependency. It says which inputs it uses, so Animate can calculate it from the requested scene state. It is not an instruction to mutate the previous frame.

There are two phases. A semantic relation uses sampled scene values and object identities. A layout relation also needs measurements from the renderer, so it is resolved after ordinary sampling.

Use a semantic relation for a point determined by other points. Use a layout relation for a box whose size depends on rendered text. The distinction is about when the necessary information is available.

The declaration also states its output structure and whether its result can be cached. The reference gives the exact dependency and cache rules. A fixed slide layout normally needs neither a new relation nor a per-frame layout pass.