Automatic merge of T1.5.1-689-g9d41208f0 and 19 pull requests

- Pull request #570 at c59c788: Experimental glTF 2.0 support with PBR lighting
- Pull request #839 at d00beb9: First phase of https://blueprints.launchpad.net/or/+spec/additional-cruise-control-parameters
- Pull request #865 at 67014b7: Dispatcher window improvements
- Pull request #874 at f8dbeab: Dynamic brake controller refactoring
- Pull request #875 at 43bf33e: Bug fix for https://bugs.launchpad.net/or/+bug/2036346 Player train switching doesn't work with 3D cabs
- Pull request #876 at f92de76: docs: add source for documents previously on website to source Documentation folder
- Pull request #878 at 3757c96: Implement Polach Adhesion
- Pull request #882 at 7fbe46c: Blueprint/train car operations UI window
- Pull request #883 at edcc2dd: SwitchPanel disconnect/connect handling
- Pull request #885 at c81447b: feat: Add notifications to Menu
- Pull request #886 at 228f0f0: Scene viewer extension to TrackViewer
- Pull request #888 at d7daf62: docs: Document player application model
- Pull request #889 at 43341cf: No speed update
- Pull request #890 at 39a9fa4: Allow depart early
- Pull request #892 at 1f5ba4c: Signal Function OPP_SIG_ID_TRAINPATH
- Pull request #893 at bf8876b: Signal errors
- Pull request #894 at 794fddf: Correct Decrease Colour
- Pull request #896 at 5866028: First implementation of https://blueprints.launchpad.net/or/+spec/specific-sounds-for-ai-trains
- Pull request #897 at 64a29c8: feat: Improved system information collection

Author: openrails-bot

Source/Documentation/Manual/physics.rst

@@ -254,7 +254,16 @@ simplicity, only one axle model is computed (and animated). A tilting
 feature and the independent axle adhesion model will be introduced in the
 future.
 
-The heart of the model is the slip characteristics (picture below).
+The advanced adhesion model uses two alternate algorithims to calculate the 
+wheel adhesion. The first model is based upon an algorithim by Pacha, whilst the second 
+uses an algorithim developed by Polach. The Polach algorithim provides 
+a more accurate outcome and facilitates the future inclusion of track conditions. 
+However it is more CPU load intensive then the Pacha one. This can produce low 
+frame rates for the screen display. Hence OR automatically sense the CPU load, 
+and switches to the Pacha algorithim at high loads and to the Polach algorithim 
+under lower CPU loads.  
+
+The heart of the adhesion algorithim is the slip characteristics (pictured below).
 
 .. image:: images/physics-adhesion-slip.png
    :align: center