normalized 8-directional sprite movement using lookup tables

move_sprite.py

def move_sprite(sprite, dt, key_up, key_down, key_left, key_right):
	"""
	returns the x and y tuple offset for normalized 8-directional movement
	sprite is expected to have x, y, x_speed, and y_speed properties
	speed is expected to be represented in pixels per second
	"""
	# Note: using legacy "mm" and "mt" variable names 
	# whose original meaning has been forgotten over the last 20 years
	mm = [0, 0, 1, 3, 1, 2, 0, 0, 3, 1, 5, 5, 5, 4, 0, 0, 2, 1, 4, 5, 4, 4]
	mt = [0, 0.0, 1.0, -1.0, 0.7071067811865475, -0.7071067811865475]
	control_code = 0
	if key_up:
		control_code = control_code | 2
	elif key_down:
		control_code = control_code | 4
	if key_left:
		control_code = control_code | 8
	elif key_right:
		control_code = control_code | 16
	if control_code > 0:
		# find the directional movement using lookup tables
		mx = mt[mm[control_code]] * sprite.x_speed
		my = mt[mm[control_code + 1]] sprite.y_speed
		next_x = sprite.x + mx * dt
		next_y = sprite.y + my * dt
		return (next_x, next_y)
	else:
		# no change in position
		return (sprite.x, sprite.y)