While the camera tracks an entity or looks at a point, Cesium measures
zoom distance from the target, not the Earth. Raising the ceiling to the
camera's altitude then lifted it with every outward step, so a tracked
camera could zoom out without limit. The guard now follows the altitude
only for an untracked 3D camera and otherwise keeps its 40,000 km
ceiling.
Above 300 km the guard treated any shrinking pinch distance as an outward
zoom, so a two-finger tilt whose fingers drifted slightly closer had its
pitch overwritten. A two-finger gesture now counts as a zoom only when the
spacing changes more than the fingers' midpoint moves.
The guard reads its input in preRender, which Cesium only fires on frames
that draw. In request-render mode, wheel input at the ceiling doesn't move
the camera, so nothing drew and the input was applied later by an
unrelated frame. The guard now requests a frame through the render
governor whenever it has unread input.
Cesium clamps any zoom that starts above maximumZoomDistance to that
limit, in either direction, so a share link or flight that left the
camera above 40,000 km jumped to the ceiling on the first wheel tick.
While the camera is above the ceiling, the guard now uses its current
height as the limit and lowers it as the camera descends.
Cesium zooms a shallow view out by backing along the cursor ray with
heading and pitch held fixed, and GEV set no zoom ceiling. Past ~700 km
the limb drops below the fixed pitch, the steps grow with height, and
the camera flies off into space.
Cap user zoom at 40,000 km (whole-Earth view; flights are not limited)
and, above 300 km during a user wheel, pinch or right-drag zoom-out,
ease the pitch down to at least 8 degrees below the Earth's limb. The
clamp yields to disabled inputs, tracked transforms and camera flights.
Sameh Khamis