This kind of relative contribution is also represented in a pie chart but
in a pie chart you're representing the contribution based on angle and
a little bit by area than on position and length.
Here in a pie chart the relative proportion of the blue category
versus the orange category versus the green category versus the yellow category
is being represented by the angle as the angle's sum to 360 degrees.
It's also proportional to the area represented by each of these four regions.
That indication can be degraded somewhat if you try to
show a pie chart in three dimensions.
And that's because in three dimensions we are still perceiving
a three dimensional scene as a two dimensional image.
And the visual cues we're using include foreshortening and perspective.
And those cues can get in the way of our ability to perceive a region, say in
the foreground, as being larger or smaller than a region in the background because of
our expectation that perspective is going to make regions in the foreground larger.
Or at least appear larger and regions in the background appear smaller,
even if it's just a orthographic non-perspective projection.
So, it's best not to use three dimensions for pie charts and, in fact,
it's better just to use a stacked bar chart instead of a pie chart.
In this case, each one of these bars can represent a separate pie chart
because it's representing the separate relative contribution to the whole of
multiple dependent variables, as they vary across some independent variable.