Implement Subframes

sailsim/simulation/Frame.py

@@ -3,6 +3,7 @@ class Frame():
 
     def __init__(self):
         self.frameNr = self.time = None
+        self.subframe = None
 
         self.windTable = []
 
@@ -28,6 +29,7 @@ def __init__(self):
     def collectSimulation(self, simulation):
         self.frameNr = simulation.frame
         self.time = simulation.getTime()
+        self.subframe = simulation.subframe
 
     def collectBoat(self, boat):
         """Collect and save all information about the boat."""
@@ -72,7 +74,7 @@ def getWindList(self):
     def getCSVLine(self):
         """Return string that contains all data about this frame."""
         data = [
-            self.frameNr, self.time,
+            self.frameNr, self.time, self.subframe,
             self.boatPosX, self.boatPosY, self.boatSpeedX, self.boatSpeedY, # self.boatDirection,
             self.boatApparentWindX, self.boatApparentWindY, self.boatApparentWindAngle, self.boatLeewayAngle, self.boatAngleOfAttack,
             self.boatForceX, self.boatForceY,

sailsim/simulation/FrameList.py

@@ -33,7 +33,7 @@ def getCSV(self):
     def getCSVHeader(self):
         """Generate head of .csv file."""
         headers = [
-            "frame", "time",
+            "frame", "time", "subframe",
             "boatPosX", "boatPosY", "boatSpeedX", "boatSpeedY", # "boatDirection",
             "boatApparentWindX", "boatApparentWindY", "boatApparentWindAngle", "boatLeewayAngle", "boatAngleOfAttack",
             "boatForceX", "boatForceY",

sailsim/simulation/Simulation.py

@@ -1,4 +1,7 @@
 from copy import deepcopy
+from math import ceil, log2
+
+from sailsim.utils.coordconversion import cartToRadius
 
 from sailsim.simulation.FrameList import FrameList
 
@@ -22,6 +25,7 @@ def __init__(self, world, timestep, lastFrame=None):
         # Timing
         self.timestep = timestep
         self.frame = 0
+        self.subframe = 0
         self.lastFrame = lastFrame
 
     def run(self):
@@ -40,15 +44,31 @@ def step(self):
         # Calculate Forces on boat
         (boatX, boatY) = self.world.boat.getPos()                           # Fetch boat position
         (windX, windY) = self.world.wind.getWindCart(boatX, boatY, time)    # Get wind
-        (forceX, forceY) = self.world.boat.resultingForce(windX, windY)
+        (forceX, forceY) = self.world.boat.resultingForce(windX, windY)     # Get resulting Force
+
+        # Subframing
+        oldSubFrame = self.subframe                         # Save old subframe
+        subframeThreshold = 2 ** 4                          # 1 / maxValue until new substep
+        deltav = cartToRadius(forceX, forceY) * self.timestep / self.world.boat.mass # calculate change of speed of boat
+        subframe = ceil(log2(deltav * subframeThreshold))   # calculate ideal subframe
+        self.subframe = min(8, max(0, subframe))            # keep subframe in interval
+
+        # Bring frame to integer values (get all binary decimal places to 0)
+        if oldSubFrame > self.subframe:     # Only run this part when simulation wants to run on a lower subframe value
+            while oldSubFrame > self.subframe and self.frame % 2**(-oldSubFrame + 1) == 0: # If ... and the oldSubFrame'th place in binary is 0
+                oldSubFrame -= 1            # decrease subframe by one
+            self.subframe = oldSubFrame     # Use calculated subframe as subframe
+
+        subfrFactor = 1 / (2 ** self.subframe)
+        # print(deltav, deltav * subfrFactor, subframe, self.subframe, sep="\t")
 
         # Save frame
         self.frameList.grabFrame(self)
-        self.frame += 1
+        self.frame += 1 * subfrFactor
 
         # Move Boat
-        self.world.boat.applyForce(forceX, forceY, self.timestep)
-        self.world.boat.moveInterval(self.timestep)
+        self.world.boat.applyForce(forceX, forceY, self.timestep * subfrFactor)
+        self.world.boat.moveInterval(self.timestep * subfrFactor)
 
 
     def getTime(self):

tests/basictest.py

@@ -24,7 +24,7 @@
 
 # Create world and simulation
 w = World(b, wind, None)
-s = Simulation(w, 0.01, 1024)
+s = Simulation(w, .03125, 256)
 
 # Simulate 1 step
 s.step()