Struct bevy::core_pipeline::motion_blur::MotionBlur

pub struct MotionBlur {
    pub shutter_angle: f32,
    pub samples: u32,
}

Expand description

A component that enables and configures motion blur when added to a camera.

Motion blur is an effect that simulates how moving objects blur as they change position during the exposure of film, a sensor, or an eyeball.

Because rendering simulates discrete steps in time, we use per-pixel motion vectors to estimate the path of objects between frames. This kind of implementation has some artifacts:

Fast moving objects in front of a stationary object or when in front of empty space, will not have their edges blurred.
Transparent objects do not write to depth or motion vectors, so they cannot be blurred.

Other approaches, such as A Reconstruction Filter for Plausible Motion Blur produce more correct results, but are more expensive and complex, and have other kinds of artifacts. This implementation is relatively inexpensive and effective.

§Usage

Add the MotionBlur component to a camera to enable and configure motion blur for that camera. Motion blur also requires the depth and motion vector prepass, which can be added more easily to the camera with the MotionBlurBundle.

commands.spawn((
    Camera3dBundle::default(),
    MotionBlurBundle::default(),
));

Fields§

§shutter_angle: f32

The strength of motion blur from 0.0 to 1.0.

The shutter angle describes the fraction of a frame that a camera’s shutter is open and exposing the film/sensor. For 24fps cinematic film, a shutter angle of 0.5 (180 degrees) is common. This means that the shutter was open for half of the frame, or 1/48th of a second. The lower the shutter angle, the less exposure time and thus less blur.

A value greater than one is non-physical and results in an object’s blur stretching further than it traveled in that frame. This might be a desirable effect for artistic reasons, but consider allowing users to opt out of this.

This value is intentionally tied to framerate to avoid the aforementioned non-physical over-blurring. If you want to emulate a cinematic look, your options are:

Framelimit your app to 24fps, and set the shutter angle to 0.5 (180 deg). Note that depending on artistic intent or the action of a scene, it is common to set the shutter angle between 0.125 (45 deg) and 0.5 (180 deg). This is the most faithful way to reproduce the look of film.
Set the shutter angle greater than one. For example, to emulate the blur strength of film while rendering at 60fps, you would set the shutter angle to 60/24 * 0.5 = 1.25. Note that this will result in artifacts where the motion of objects will stretch further than they moved between frames; users may find this distracting.

§samples: u32

The quality of motion blur, corresponding to the number of per-pixel samples taken in each direction during blur.

Setting this to 1 results in each pixel being sampled once in the leading direction, once in the trailing direction, and once in the middle, for a total of 3 samples (1 * 2 + 1). Setting this to 3 will result in 3 * 2 + 1 = 7 samples. Setting this to 0 is equivalent to disabling motion blur.