docs/2016-11-02-direction.md

+---
+layout: post
+title: Direction strategies
+subtitle: 
+#bigimg: /img/jupedsim_small.png
+permalink: 2016-11-02-direction.html
+---
+
+
+The desired direction of a pedestrian is defined following different algorithms:
+In the section of the chosen model the direction strategy should be specified as follows:
+
+```xml
+<exit_crossing_strategy>num</exit_crossing_strategy>
+```
+
+with *num* a positive integer.
+
+The majority of the strategies define how a pedestrian crosses a line $$L = [P_1, P_2]$$. Possible values are:  
+
+1. The direction of the pedestrian is towards the middle of $$L$$ ($$\frac{P_1+P2}{2}$$)  
+
+2. The direction is given by the nearest point on $$L$$ to the position of the pedestrian.  
+   $$L$$ is shorten by 20 cm.  
+
+3. If the nearest point of the pedestrian on the segment line $$L$$ is outside the segment, then chose the middle point as target.  
+   Otherwise the nearest point is chosen.
+
+4. This strategy is still beta. It assumes that the simulation scenario has no loops or U-shaped corridors.
+   Pedestrians,  target he exit, even if it is outside their visibility range. In case of intersection with walls or obstacles, the temporary direction is rotated away from the wall.  
+
+5. Does not exist.
+
+6. -9. Strategies using floor fields (ff) (vector fields); one ff per target (door, line, ...)
+
+<img src="
+https://cst.version.fz-juelich.de/jupedsim/jpscore/uploads/785cda284f5f44d2b019332d29b8075e/transformFF.png" width="300" height="300" />
+
+  * 6: This strategy does use a floor field rather than heading towards a point on a line segment.
+
+    For more details see this talk [^talk_arne] and the corresponding thesis [^thesis_arne].
+     
+    (__do not use in multi-storage buildings__)
+    
+  * 7: (__experimental__)
+  
+  * 8: This strategy uses a floor field collection for each room. 
+
+    Thus the floor fields are smaller but cannot steer to targets in a different room. 
+
+    The router __must__ provide intermediate targets for every agent, the target being in the same room.
+    
+    The projection of the room onto the ($$x,\, y$$)-plane must be non-overlapping!
+
+  * 9: This strategy uses a floor field collection for each subroom. (__broken__)
+
+    Thus the floor fields are again smaller but cannot steer to targets in a different subroom. 
+
+    The router __must__ provide intermediate targets for every agent, that target being in the same subroom.
+    
+    The projection of the room onto the ($$x,\, y$$)-plane must be non-overlapping!
+
+---   
+
+
+[^talk_arne]: (https://fz-juelich.sciebo.de/index.php/s/s1ORGTUssCsHDHC)  
+[^thesis_arne]: (https://fz-juelich.sciebo.de/index.php/s/VFnUCH2gtz1mSoL)  
+
+    
+[#Chraibi2011]: http://aimsciences.org/journals/displayPaper.jsp?paperID=6440 "Chraibi el al. Force-based models of pedestrian dynamics.  Pages: 425 - 442, Volume 6, Issue 3, September 2011"
+
+