How is fall damage calculated in Risk of Rain?

Characters in the game suffer from fall damage when dropping from high places. A few observations from playing the game:

• Fall damage seems to be capped. I can't tell if it is a percentage of total health or a fixed number, but this does make it difficult to die from fall damage.
• Certain skills can negate fall damage, like the Commando's Tactical Roll.
• Certain items triggered by damage is also triggered by fall damage.

I would like to know if there is a formula for fall damage, if the cap is a fixed number or a percentage of total health, and if armor has any effect on fall damage.

Fall damage is calculated as a percent of maximum health. If you have a shield from Guardian Heart, however, and the fall damage you would take is more than the size of your shield, it instead only does as much damage as the shield can absorb. This much I know from experience.
I can't find any information about the effect of damage reduction anywhere though, so I'll have to do some experimentation...

I'll update my answer when I've finished.