Voxel artifacts when clipping past bounds

[lilleyse]

The clipping bounds should never be allowed to exceed the bounds, but that seems to be happening with cylinders and ellipsoids.

Sandcastle

The best place to start looking is here:

cesium/packages/engine/Source/Scene/VoxelCylinderShape.js

Lines 259 to 260 in b68be0e

	const renderMinAngle = Math.max(shapeMinAngle, clipMinAngle);
	const renderMaxAngle = Math.min(shapeMaxAngle, clipMaxAngle);

This is actually a somewhat hard problem

• This code does not handle the -pi / pi discontinuity properly
• In theory clipping should be able to produce a two-wedge shape like below, but this requires significant shader changes

(Black = bounds, magenta = clipping bounds)