= Light transport =

== Radiometry recap ==

What is radiant flux?
* total amount of energy passing through a surface (measured per second)
* Radiant flux in Watts or Joules/second

=== Why do we not use radiant flux? ===

* When we emasure a high flux val, we dont know if lots of energy through a
  small surface, or a little energy through a huge surface
* TLDR its to ambiguous

New unit irradiance
* Flux per unit area
* IE Watt/m^2

=== Why do we not use irradiance? ===

We know the surface, but we still need an angle
* Could be lost of energy in a huge angle
* little energy in a small angle

New unit Radiance
* Flux per unit area angle
* W / (m^2 * radians)

== Basic question ==

How do we calculate how much light exits a surface point in a given direction

[[maxwell_equations|Maxwell equations]]!