Added some documentation for the new reference mode features.

changelog.md

@@ -5,11 +5,13 @@
 **New Features:**
 
   * Added support for Depth of Field in reference path tracing mode.
+  * Added free camera controls when the game is paused. See the [Readme](readme.md) for more information.
 
 **Fixed Issues:**
 
   * Fixed a crash that happened at map load time when a custom map has no analytic lights.
   * Reduced the noise in the `biggun` map next to the barred windows.
+  * Reduced the noise from yellow lamps next to the entrance of the `jail4` map at night.
 
 ## 1.2.1
 

doc/client.md

@@ -804,6 +804,9 @@ to disable fake specular. Default value is 0.2.
 #### `pt_focus`
 Sets the distance to the focal plane for the Depth of Field effect.
 
+#### `pt_freecam`
+Enables free floating camera when the game is paused. Default value is 1.
+
 #### `pt_light_stats`
 Enables an experimental algorithm that improves light sampling quality by 
 counting rays that hit or missed a particular light from a given BSP cluster.

readme.md

@@ -145,6 +145,30 @@ In the game, music playback is enabled when console variable `ogg_enable` is set
 
 Music playback support is using code adapted from the [Yamagi Quake 2](https://www.yamagi.org/quake2/) engine.
 
+## Reference Path Tracing Mode
+
+When a single player game or demo playback is paused, normally with the `pause` key, the reference mode activates. 
+In this mode, denoisers and some other real-time rendering approximations are disabled, and the image is produced
+using accumulation rendering instead. This means that the engine renders the same frame hundreds or thousands of times,
+with different noise patterns, and averages the results. Once the image is stable enough, you can save a screenshot.
+
+In addition to rendering higher quality images, the reference mode has some unique features. One of them is the
+**Depth of Field** (DoF) effect, which simulates camera aperture and defocus blur, or bokeh. In contrast with DoF effects
+used in real-time renderers found in other games, this implementation computes "true" DoF, which works correctly through reflections and refractions, and has no edge artifacts. Unfortunately, it produces a lot of noise instead, so thousands
+of frames of accumulation are often needed to get a clean picture. To control DoF in the game, use the mouse wheel and 
+`Shift/Ctrl` modifier keys: wheel alone adjusts the focal distance, `Shift+Wheel` adjusts the aperture size, and `Ctrl` makes
+the adjustments finer.
+
+Another feature of the reference mode is free camera controls. Once the game is paused, you can move the camera and 
+detach it from the character. To move the camera, use the regular `W/A/S/D` keys, plus `Q/E` to move up and down. `Shift` makes
+movement faster, and `Ctrl` makes it slower. To change orientation of the camera, move the mouse while holding the left 
+mouse button. To zoom, move the mouse up or down while holding the right mouse button. Finally, to adjust camera roll,
+move the mouse left or right while holding both mouse buttons.
+
+Settings for all these features can be found in the Video menu. To adjust the settings from the console, see the
+`pt_accumulation_rendering`, `pt_dof`, `pt_aperture`, `pt_freecam` and some other similar console variables in the 
+[Client Manual](doc/client.md).
+
 ## MIDI Controller Support
 
 The Quake II console can be remote operated through a UDP connection, which