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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
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