CRT Filter

If you’d like an 80s feel to your games, you can use the built-in CRT filter.

You can create a CRT filter with code like this:

# Create the crt filter
self.crt_filter = CRTFilter(width, height,
                            resolution_down_scale=6.0,
                            hard_scan=-8.0,
                            hard_pix=-3.0,
                            display_warp = Vec2(1.0 / 32.0, 1.0 / 24.0),
                            mask_dark=0.5,
                            mask_light=1.5)

You can play around with the parameters to get an idea of what they do. For example:

Resolution Down Sampling

resolution_down_scale = 1

resolution_down_scale = 6

To use the CRT Filter, your on_draw method should first draw everything to the CRT filter. At this point, nothing draws to the screen, we are just drawing to an internal frame buffer.

Then, once everything is drawn to the CRT filter, render that filter to the screen.

# Draw our stuff into the CRT filter instead of on screen
self.crt_filter.use()
self.crt_filter.clear()
self.sprite_list.draw()

# Next, switch back to the screen and dump the contents of the CRT filter
# to it.
self.use()
self.clear()
self.crt_filter.draw()

Full Example Code

The example code just animates a Pac-Man image. You can toggle the CRT filter on or off by hitting the space bar.

Images to run this example can be found here: https://github.com/pythonarcade/arcade/tree/development/doc/tutorials/crt_filter

import arcade
from arcade.experimental.crt_filter import CRTFilter
from pyglet.math import Vec2


# Store our screen dimensions & title in a convenient place
SCREEN_WIDTH = 800
SCREEN_HEIGHT = 1100
SCREEN_TITLE = "ShaderToy Demo"


class MyGame(arcade.Window):

    def __init__(self, width, height, title):
        super().__init__(width, height, title, resizable=True)

        # Create the crt filter
        self.crt_filter = CRTFilter(width, height,
                                    resolution_down_scale=6.0,
                                    hard_scan=-8.0,
                                    hard_pix=-3.0,
                                    display_warp=Vec2(1.0 / 32.0, 1.0 / 24.0),
                                    mask_dark=0.5,
                                    mask_light=1.5)

        self.filter_on = True

        # Create some stuff to draw on the screen
        self.sprite_list = arcade.SpriteList()

        full = arcade.Sprite("Pac-man.png")
        full.center_x = width / 2
        full.center_y = height / 2
        full.scale = width / full.width
        self.sprite_list.append(full)

        my_sprite = arcade.Sprite(
            "pac_man_sprite_sheet.png",
            scale=5, image_x=4, image_y=65, image_width=13, image_height=15)
        my_sprite.change_x = 1
        self.sprite_list.append(my_sprite)
        my_sprite.center_x = 100
        my_sprite.center_y = 300

        my_sprite = arcade.Sprite(
            "pac_man_sprite_sheet.png",
            scale=5, image_x=4, image_y=81, image_width=13, image_height=15)
        my_sprite.change_x = -1
        self.sprite_list.append(my_sprite)
        my_sprite.center_x = 800
        my_sprite.center_y = 200

        my_sprite = arcade.AnimatedTimeBasedSprite()
        texture = arcade.load_texture(
            "pac_man_sprite_sheet.png", x=4, y=1, width=13, height=15)
        frame = arcade.AnimationKeyframe(tile_id=0,
                                         duration=150,
                                         texture=texture)
        my_sprite.frames.append(frame)
        texture = arcade.load_texture(
            "pac_man_sprite_sheet.png", x=20, y=1, width=13, height=15)
        frame = arcade.AnimationKeyframe(tile_id=1,
                                         duration=150,
                                         texture=texture)
        my_sprite.frames.append(frame)

        my_sprite.change_x = 1
        self.sprite_list.append(my_sprite)
        my_sprite.center_x = 0
        my_sprite.center_y = 300
        my_sprite.texture = texture
        my_sprite.scale = 5.0

    def on_draw(self):
        if self.filter_on:
            # Draw our stuff into the CRT filter instead of on screen
            self.crt_filter.use()
            self.crt_filter.clear()
            self.sprite_list.draw()

            # Next, switch back to the screen and dump the contents of
            # the CRT filter to it.
            self.use()
            self.clear()
            self.crt_filter.draw()
        else:
            # Draw our stuff into the screen
            self.use()
            self.clear()
            self.sprite_list.draw()

    def on_update(self, dt):
        # Keep track of elapsed time
        self.sprite_list.update()
        self.sprite_list.update_animation(dt)
        for sprite in self.sprite_list:
            if sprite.left > self.width and sprite.change_x > 0:
                sprite.right = 0
            if sprite.right < 0 and sprite.change_x < 0:
                sprite.left = self.width

    def on_key_press(self, key, mod):
        if key == arcade.key.SPACE:
            self.filter_on = not self.filter_on


if __name__ == "__main__":
    MyGame(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_TITLE)
    arcade.run()