flame sim example

demo example that simulates small flame in display - with masking for
shape

examples/flame_simulation.py

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+### Flame simulation on the Microbit.
+### Author: M. Schafer 2016
+# This program has been placed into the public domain.
+
+import microbit, random
+
+# User adjustable values for range of brightness in flames.
+MIN_BRIGHTNESS = 1
+MAX_BRIGHTNESS = 8
+
+
+#  fixed for the Microbit
+DISPLAY_WIDTH  = 5
+DISPLAY_HEIGHT = 5
+
+INVERT_DISPLAY = True # flame can be oriented in either direction
+
+# MASK to create fire shape. multiplies values %
+MASK = [[ 88, 100, 100, 100, 88 ],
+        [ 60,  95, 100,  95, 60 ],
+        [ 50,  88,  90,  88, 50 ],
+        [ 33,  75,  88,  75, 33 ],
+        [ 10,  33,  66,  33, 10 ]  ]
+
+# Generate a new bottom row of random values for the flames
+def generate_line(start=MIN_BRIGHTNESS, end=MAX_BRIGHTNESS):
+    "start and end define range of dimmest to brightest 'flames'"
+    return [start + random.randrange(end-start) for i in range(DISPLAY_WIDTH)]
+
+# shift all values in the grid up one row
+def shift_up(grid, newline):
+    "Shift up lines in grid, add newline at bottom"
+    for y in range(DISPLAY_HEIGHT-1, 0, -1):
+        grid[y] = grid[y-1]
+    # lowest line
+    for x in range(DISPLAY_WIDTH):
+        grid[0] = newline
+
+
+# write a frame to the screen.
+# Interpolate values based on percent
+def interpolate_frame(screen, pcnt, grid, line):
+    """ Interpolate new values by reading from grid and
+         writing to the screen """
+    # each row interpolates with the one before it
+    for y in range(DISPLAY_HEIGHT-1, 0, -1):
+        for x in range(DISPLAY_WIDTH):
+            mask = MASK[y][x]
+            newval = ((100-pcnt) * grid[y][x] + pcnt * grid[y-1][x] ) / 100.0
+            newval = mask * newval / 100.0
+            if INVERT_DISPLAY:
+                screen.set_pixel(x, DISPLAY_HEIGHT-y-1, int(newval))
+            else:
+                screen.set_pixel(x, y, int(newval))
+    # first row interpolates with the "next" line
+    for x in range(DISPLAY_WIDTH):
+        mask = MASK[y][x]
+        newval = ((100-pcnt) * grid[0][x] + pcnt * line[x]) / 100.0
+        newval = mask * newval / 100.0
+        if INVERT_DISPLAY:
+            screen.set_pixel(x, DISPLAY_HEIGHT-1, int(newval))
+        else:
+            screen.set_pixel(x, 0, int(newval))
+
+## Setup
+line = generate_line()
+grid = [[0 for i in range(DISPLAY_WIDTH)] for i in range(DISPLAY_HEIGHT)]
+
+SCREEN = microbit.display
+percent = 0     # counter to see when to re-interpolate
+sleeptime = 0   # delay between updates
+percent_increment = 25  # how fast we interpolate fire
+
+
+# loop forever
+while True:
+    if percent > 100:
+        # move everything up a line, insert new bottom row
+        line = generate_line()
+        shift_up(grid, line)
+        percent = 0
+
+    # Check Buttons to see if changing
+    # button_a = smoothness
+    if microbit.button_a.was_pressed():
+        percent_increment += 5
+        if percent_increment > 50:
+             percent_increment = 1
+        print("percent interpolate=", percent_increment)
+    # button_b = delay
+    if microbit.button_b.was_pressed():
+        sleeptime += 10
+        if sleeptime > 100:
+             sleeptime = 0
+        print("sleeptime=", sleeptime)
+    # draw frame and sleep
+    interpolate_frame(SCREEN, percent, grid, line)
+    microbit.sleep(sleeptime)
+    # update main counters
+    percent += percent_increment
+