Controlling rain droplets on sensor¶

Bifrost supports rain effects and camera lens droplets to simulate wet weather conditions. Rain is controlled through world.env.weather, while lens droplets are a per-camera property controlled through camera.screen_droplets. They can be used independently or together.

MEDIUM — Small running droplets on the camera lens

VERY_LARGE — Very large droplets on the camera lens

Rain intensity¶

Rain intensity controls the amount of rain particles in the scene.

Example: setting rain intensity¶

# Set rain intensity (0.0 to 10.0)
world.env.weather.set_rain_intensity(5.0)

Screen droplet presets¶

Screen droplets simulate water droplets on a camera’s lens. Because the effect belongs to the sensor rather than the world, it is set per camera — in multi-camera scenes each camera carries its own droplets. You can apply a preset to quickly set a desired level of droplet coverage using ScreenDropletsPreset.

Example: applying a screen droplet preset¶

world.camera.screen_droplets.set_preset(ScreenDropletsPreset.HEAVY)

`bbi.ScreenDropletsPreset.NONE`	No droplets on the camera lens
`bbi.ScreenDropletsPreset.LIGHT`	Small droplets on the camera lens
`bbi.ScreenDropletsPreset.MEDIUM`	Small running droplets on the camera lens
`bbi.ScreenDropletsPreset.HEAVY`	Large running droplets on the camera lens
`bbi.ScreenDropletsPreset.VERY_LARGE`	Very large droplets on the camera lens

Note

Setting a new screen droplet preset resets any fine-grained overrides you may have applied to that camera. If you want to customize individual droplet parameters, apply the preset first and then set the overrides.

Deprecated since version The: world.env.weather.set_rain_screen_droplets* methods are deprecated and have no effect. Screen droplets moved to individual cameras: use camera.screen_droplets instead.

Fine-grained droplet control¶

For more precise control, you can override individual droplet parameters on top of a preset.

Method	Description
`set_blur(blur)`	Controls the blur intensity of droplets on the lens. A value of `0` produces streaking raindrops. Range: `0.0` to `1.0`
`set_speed(speed)`	Controls how quickly droplets scroll vertically across the screen. Negative values scroll downward, positive values scroll upward. Range: `-1.0` to `1.0`
`set_scroll_offset_x(offset_x)`	Sets the horizontal starting position of the droplet pattern on the screen. Range: `0.0` to `1.0`
`set_scroll_offset_y(offset_y)`	Sets the vertical starting position of the droplet pattern on the screen. Range: `0.0` to `1.0`
`set_drips_intensity(intensity)`	Controls the intensity of drip streaks running down the lens. Range: `0.0` and above
`set_scale(scale)`	Controls the size of the droplets on the screen. Range: greater than `0.0` up to `1.0`

Example: customizing droplet parameters on top of a preset¶

# Start with a preset
world.camera.screen_droplets.set_preset(ScreenDropletsPreset.MEDIUM)

# Override specific parameters
world.camera.screen_droplets.set_blur(0.5)
world.camera.screen_droplets.set_speed(-0.3)
world.camera.screen_droplets.set_drips_intensity(1.5)

Animating rain and droplets¶

Rain and droplet parameters can be animated through scenario keyframes, allowing them to vary across frames. Rain intensity is keyframed on the weather, while droplet parameters are keyframed on the camera they belong to.

Example: animating rain and droplets over time¶

world.env.set_preset("rainy_a")

scenario = world.new_scenario(num_frames=10)

for frame_idx in range(scenario.num_frames):
    scenario.set_keyframe(
        world.env.weather,
        frame_idx,
        rain_intensity=rng.uniform(2, 8),
    )
    scenario.set_keyframe(
        world.camera,
        frame_idx,
        screen_droplets=rng.choice(list(ScreenDropletsPreset)),
        screen_droplets_blur=rng.uniform(0, 0.5),
        screen_droplets_speed=rng.uniform(-0.5, 0),
    )

Tip

When randomizing rain, pair rain_intensity with a matching screen_droplets preset to keep the visual effect consistent. For example, higher rain intensities look more natural with HEAVY or VERY_LARGE droplet presets.