Make animations smoother in Audio Spectrum demo (#972)

audio/spectrum/project.godot

@@ -12,17 +12,17 @@ config_version=5
 
 config/name="Audio Spectrum Demo"
 config/description="This is a demo showing how a spectrum analyzer can be built using Godot."
+config/tags=PackedStringArray("audio", "demo", "official", "visualization")
 run/main_scene="res://show_spectrum.tscn"
-config/features=PackedStringArray("4.0")
+config/features=PackedStringArray("4.1")
 run/low_processor_mode=true
 config/icon="res://icon.webp"
-config/tags=PackedStringArray("audio", "demo", "official", "visualization")
 
 [display]
 
-window/vsync/vsync_mode=0
 window/stretch/mode="canvas_items"
 window/stretch/aspect="expand"
+window/vsync/vsync_mode=0
 
 [rendering]
 

audio/spectrum/show_spectrum.gd

@@ -1,24 +1,27 @@
 extends Node2D
 
+
 const VU_COUNT = 16
 const FREQ_MAX = 11050.0
 
 const WIDTH = 800
 const HEIGHT = 250
-
+const HEIGHT_SCALE = 8.0
 const MIN_DB = 60
+const ANIMATION_SPEED = 0.1
 
 var spectrum
+var min_values = []
+var max_values = []
+
 
 func _draw():
-	@warning_ignore("integer_division")
 	var w = WIDTH / VU_COUNT
-	var prev_hz = 0
-	for i in range(1, VU_COUNT + 1):
-		var hz = i * FREQ_MAX / VU_COUNT
-		var magnitude = spectrum.get_magnitude_for_frequency_range(prev_hz, hz).length()
-		var energy = clampf((MIN_DB + linear_to_db(magnitude)) / MIN_DB, 0, 1)
-		var height = energy * HEIGHT
+	for i in range(VU_COUNT):
+		var min_height = min_values[i]
+		var max_height = max_values[i]
+		var height = lerp(min_height, max_height, ANIMATION_SPEED)
+
 		draw_rect(
 				Rect2(w * i, HEIGHT - height, w - 2, height),
 				Color.from_hsv(float(VU_COUNT * 0.6 + i * 0.5) / VU_COUNT, 0.5, 0.6)
@@ -44,13 +47,35 @@ func _draw():
 				true
 		)
 
+
+func _process(_delta):
+	var data = []
+	var prev_hz = 0
+
+	for i in range(1, VU_COUNT + 1):
+		var hz = i * FREQ_MAX / VU_COUNT
+		var magnitude = spectrum.get_magnitude_for_frequency_range(prev_hz, hz).length()
+		var energy = clampf((MIN_DB + linear_to_db(magnitude)) / MIN_DB, 0, 1)
+		var height = energy * HEIGHT * HEIGHT_SCALE
+		data.append(height)
 		prev_hz = hz
 
+	for i in range(VU_COUNT):
+		if data[i] > max_values[i]:
+			max_values[i] = data[i]
+		else:
+			max_values[i] = lerp(max_values[i], data[i], ANIMATION_SPEED)
+
+		if data[i] <= 0.0:
+			min_values[i] = lerp(min_values[i], 0.0, ANIMATION_SPEED)
 
-func _process(_delta):
 	# Sound plays back continuously, so the graph needs to be updated every frame.
 	queue_redraw()
 
 
 func _ready():
 	spectrum = AudioServer.get_bus_effect_instance(0, 0)
+	min_values.resize(VU_COUNT)
+	max_values.resize(VU_COUNT)
+	min_values.fill(0.0)
+	max_values.fill(0.0)