Stroke tapering and fading

In some cases it would be very useful to be able to set the ends of a stroke to taper (thickness) or fade off (opacity).

Some sample use cases:

• A chain that goes into water and fades as the water gets deeper.

• A rope going around a barrel. The rope would look thinner on the sides of the barrel.

• A staircase or ramp shadow that would get darker as the elevation gets deeper.