Rumble / Haptic Feedback

Simulant provides rumble (haptic feedback) support for game controllers. Rumble effects can add tactile feedback for events like weapon fire, collisions, or pickups.

Checking for Rumble Support

Not all controllers support rumble. You can check whether a controller has rumble capability before attempting to trigger it:

auto controller = input_state->game_controller(0);
if (controller->has_rumble_effect()) {
    // Controller supports rumble
}

You can also check the has_rumble field of the GameControllerInfo struct when enumerating connected controllers.

Starting a Rumble Effect

To trigger a rumble effect, call start_rumble() on a GameController instance:

auto controller = input_state->game_controller(0);
controller->start_rumble(0.5f, 0.8f, smlt::Seconds(1.0f));

The start_rumble() method takes three arguments:

Parameter	Type	Description
low_rumble	float	Intensity of the low-frequency motor (0.0f to 1.0f)
high_rumble	float	Intensity of the high-frequency motor (0.0f to 1.0f)
duration	smlt::Seconds	How long the rumble should play

The intensity values are normalised, where 0.0f is no rumble and 1.0f is maximum intensity.

Low vs High Frequency Motors

Most modern gamepads have two rumble motors:

• Low-frequency motor - Produces a deep, heavy vibration. Good for impacts, explosions, and heavy impacts.
• High-frequency motor - Produces a sharper, lighter vibration. Good for hits, scrapes, and subtle feedback.

By mixing the two you can create a wide range of tactile effects. For example:

// Heavy explosion - mostly low rumble
controller->start_rumble(1.0f, 0.2f, smlt::Seconds(0.5f));

// Sharp hit - mostly high rumble
controller->start_rumble(0.1f, 0.9f, smlt::Seconds(0.15f));

// Continuous engine rumble - balanced
controller->start_rumble(0.4f, 0.4f, smlt::Seconds(2.0f));

Stopping Rumble

To stop any active rumble effect before it finishes:

controller->stop_rumble();

This immediately halts all rumble motors on the controller.

Platform Notes

Dreamcast

On the Dreamcast platform only the low_rumble parameter has an effect. The high-frequency motor is not supported.

General

Rumble support and behaviour may vary across platforms and controller types. Always check has_rumble_effect() before starting a rumble to avoid silent failures.

Example: Rumble on Collision

Here is a simple example of integrating rumble into a collision handler:

void on_collision(StageNode* self, StageNode* other) {
    auto controller = input_state->game_controller(0);
    if (controller && controller->has_rumble_effect()) {
        // Short sharp rumble for a hit
        controller->start_rumble(0.6f, 0.9f, smlt::Seconds(0.2f));
    }
}

Example: Rumble Duration Management

If you need a rumble effect that persists for an unknown duration (e.g. while the player is charging a weapon), you can re-trigger the rumble each frame:

void update(float dt) {
    auto controller = input_state->game_controller(0);
    if (controller && controller->has_rumble_effect() && is_charging_) {
        // Keep re-triggering a short rumble while charging
        controller->start_rumble(charge_level_, charge_level_ * 0.5f, smlt::Seconds(0.1f));
    }
}

When the charging is complete, call stop_rumble() to end the effect cleanly.