---
type: Rendering Constraint
title: Globe to Mercator morph
description: Geographic overlays must remain ground-attached through Mapbox zoom 5–6 morphing.
tags: [mapbox, globe, mercator, overlay]
visibility: public
---

# Constraint

For the Mapbox globe, `5 < zoom < 6` is a distinct globe-to-Mercator morph
mode. A custom layer must not independently mix globe and Mercator coordinates
inside this interval.

# Required approach

Use a surface projected by Mapbox, such as a `CanvasSource` or another draped
path, during the morph. Return a GPU custom layer only at `zoom <= 5` or
`zoom >= 6`.

# Verification points

Every changed geographic overlay must be checked at zoom values `4.99`, `5`,
`5.5`, `6`, and `6.01`, including zoom while the camera is moving.

The overlay must not:

- Change its visible geographic radius.
- Detach from the ground.
- Lose accumulated history when switching renderer.