One of the problems with perspective is foreshortening - the inability to compare heights at different distances.

This reminds me of one of my favourite Father Ted sketches...

"ok one last time.." (showing Father Dougal some toy cows)

"these are small, but the ones out there are far away."

"small..."

"far away..."

This is why using 3d pie charts are a bad idea - foreshortening distorts the angles, which are difficult enough to compare to begin with.

## There are 3 types of 3d.

**Perspective** : given two objects of the same height, the further away one looks smaller.

**Reverse Perspective**: given two objects of the same height, the one closer to you looks smaller. This looks really confusing and surreal.

**Orthographic**: if two objects are the same height,** they appear to have the same height irrespective of distance**. This happens because the light travels in parallel lines, rather than radiating out from the observer point - you're seeing the view from an infinite distance away.

## The advantage of the Orthographic Camera

Blender is capable of rendering using an orthographic camera, and these allow us to compare the heights of mountains. We don't need to concern ourself with how far away something is; this preserving of height at any distance means we can easily compare heights of two separate maps.

This profile comparison compares the heights of the Ben Nevis ridge and the terrain around Edinburgh. The high point in Edinburgh is Arthurs' Seat - to its left is Castle Rock and Corstorphine Hill. Behind it in White is the Ben Nevis ridge, looking from the NW.