Intensity

The Intensity procedures deal with a single scalar intensity.

As a result, they are very versatile: The value can be mapped to the power of a light, the rotation of a hammer, the press of a key, etc.

Intensity base class

The Intensity base class defines common parameters, but does not implement any animation.

The min_intensity and max_intensity parameters linearly curve MIDI velocities to their corresponding intensity.

For example, setting min_intensity=0.5 and max_intensity=1.0 will map MIDI velocities (0, 127) to intensities (0.5, 1.0).

IntensityOnOff

The IntensityOnOff class turns on when a message starts, and turns off when it ends.

The intensity turns on at the time the message starts; that is, it begins transitioning to on a bit before that time.

Similarly, it stays on until the message ends, and then transitions to off a bit after that time.

The magnitude to which it turns on is determined by min_intensity, max_intensity, and the MIDI velocity.

Set the duration parameter to the time spent transitioning between states.

IntensityOnOff(
    midi=midi,
    animkey=animkey,
)

IntensityOnOff(
    ...
    duration=0.1,
)

IntensityFade

The IntensityFade class transitions to the peak intensity when a message starts, and fades gradually over time.

Actually, IntensityFade is very versatile. It can do much more than fade out. More about this later.

The default configuration uses an exponential decay.

Customize the falloff by assigning fade_func, a function that takes in time in seconds since the note started and returns a multiplicative factor.

IntensityFade(
    midi=midi,
    animkey=animkey,
)

# Customize with builtin interpolation.

exp_factor = 0.5
IntensityFade(
    ...
    fade_func=lambda t: bmusic.utils.EXPONENTIAL(exp_factor, t),
)

lin_factor = 0.5
IntensityFade(
    ...
    fade_func=lambda t: bmusic.utils.LINEAR(lin_factor, t),
)

IntensityFade has features to prevent unnecessary keyframing on every frame:

• key_interval: The interval in frames between keyframes. Often, Blender’s interpolation is good enough to not need a keyframe on every frame.

• off_thres: When the intensity falls below this value, the animation is turned off. This is useful to prevent unnecessary keyframing when the intensity is very low.

• max_len: The maximum length of the animation. This is useful to prevent the animation from running indefinitely.

---

Customizing fade_func makes it possible to create a variety of effects.

If your fade_func is not monotonic decreasing, make sure to set off_thres to a negative value, to prevent the procedure from cutting off the animation at an inappropriate time.

For example, combining EXPONENTIAL and OSCILLATE creates an oscillation that decays.

IntensityFade(
    ...
    fade_func=lambda t: bmusic.utils.EXPONENTIAL(0.5, t) * bmusic.utils.OSCILLATE(0.3, t),
    off_thres=-1,
)