Improve readability & controls of sprite depth example

arcade/experimental/sprite_depth_cosine.py

@@ -0,0 +1,91 @@
+"""
+Depth-sort sprites using a depth buffer in the GL context.
+
+Press the space bar to toggle depth testing during drawing.
+
+During each update, the depth of each sprite is updated to follow a
+cosine wave. Afterward, the following is drawn:
+
+ * All sprites in depth-sorted order
+ * A white square centered over each sprite along the x-axis, and moving
+   with the wave along the y-axis
+
+If Python and Arcade are installed, this example can be run from the command line with:
+python -m arcade.experimental.sprite_depth_cosine
+"""
+import math
+import arcade
+from pyglet.graphics import Batch
+
+
+# All constants are in pixels
+WIDTH, HEIGHT = 800, 600
+
+NUM_SPRITES = 10
+
+SPRITE_X_START = 150
+SPRITE_X_STEP = 50
+SPRITE_Y = HEIGHT // 2
+
+DOT_SIZE = 10
+
+
+class MyGame(arcade.Window):
+
+    def __init__(self):
+        super().__init__(WIDTH, HEIGHT, "Sprite Depth Testing Example w/ a Cosine Wave")
+
+        texture = arcade.load_texture(":resources:images/test_textures/xy_square.png")
+        self.text_batch = Batch()
+
+        self.use_depth: bool = True
+        self.text_use_depth = arcade.Text(
+            "SPACE: Toggle depth testing (True)",
+            start_x=10, start_y=30, font_size=15, color=arcade.color.WHITE,
+            batch=self.text_batch
+        )
+
+        self.sprite_list = arcade.SpriteList()
+        self.time = 0.0
+
+        for i in range(NUM_SPRITES):
+            sprite = arcade.Sprite(
+                texture,
+                center_x=SPRITE_X_START + SPRITE_X_STEP * i,
+                center_y=SPRITE_Y
+            )
+            self.sprite_list.append(sprite)
+
+    def on_draw(self):
+        self.clear()
+
+        if self.use_depth:
+            # This context manager temporarily enables depth testing
+            with self.ctx.enabled(self.ctx.DEPTH_TEST):
+                self.sprite_list.draw()
+        else:
+            self.sprite_list.draw()
+
+        # Draw wave visualization markers over each sprite
+        for i, sprite in enumerate(self.sprite_list):
+            arcade.draw_point(
+                SPRITE_X_START + SPRITE_X_STEP * i, SPRITE_Y + sprite.depth,
+                arcade.color.WHITE, DOT_SIZE
+            )
+
+        self.text_batch.draw()
+
+    def on_key_press(self, symbol: int, modifiers: int):
+        if symbol == arcade.key.SPACE:
+            self.use_depth = not self.use_depth
+            self.text_use_depth.text = f"SPACE: Toggle depth testing ({self.use_depth})"
+
+    def on_update(self, delta_time):
+        self.time += delta_time
+
+        for i, sprite in enumerate(self.sprite_list):
+            sprite.depth = math.cos(self.time + i) * SPRITE_X_STEP
+
+
+if __name__ == "__main__":
+    MyGame().run()