Mouse.posChange

Description

How much has the mouse moved during this frame? This is normally just the change in pos, measured in pixels. In relative mouse mode pos is frozen and this becomes the only source of motion, in the mouse’s raw device units rather than pixels.

Examples

Mouse look

MouseMode.Relative is what you want for mouse-look style camera control. The cursor is hidden and pinned in place, so Mouse.pos stops changing, and Mouse.posChange becomes the only report of mouse motion. The pointer never reaches the edge of the screen, so the view can keep turning as far as the user cares to spin.

Capture the mouse only while the user is actually looking around, and hand it back when they let go, so the rest of the time they still have a cursor to click with. Note that posChange is an amount of motion rather than a speed, so unlike a velocity it should not be scaled by Time.Stepf. Doing that would tie the sensitivity to the frame rate.

float lookYaw;
float lookPitch;
void MouseLook()
{
	// The Simulator mode already provides a mouselook, and XR doesn't need
	// one, so this is only really useful in Window mode.
	if (SK.Settings.mode != AppMode.Window)
		return;

	if (Input.Key(Key.MouseRight).IsJustActive  ()) Input.MouseMode = MouseMode.Relative;
	if (Input.Key(Key.MouseRight).IsJustInactive()) Input.MouseMode = MouseMode.Normal;
	if (Input.MouseMode != MouseMode.Relative) return;

	// Relative mode reports raw mouse units instead of pixels, so this is
	// degrees per unit of motion, and wants tuning by feel.
	const float sensitivity = 0.1f;
	lookYaw   -= Input.Mouse.posChange.x * sensitivity;
	lookPitch -= Input.Mouse.posChange.y * sensitivity;
	// Stop just shy of straight up and down, or the view rolls over the top
	lookPitch  = Math.Clamp(lookPitch, -89.9f, 89.9f);

	Renderer.CameraRoot = Matrix.R(lookPitch, lookYaw, 0);
}

Found an issue with these docs, or have some additional questions? Create an Issue on Github!