Orbit

since 0.7.0 Views, picking and input

Open the live demo · Read the source · View on GitHub

OrbitController already turns the camera as you drag, in every page of this showcase. This page is about three things it also does that a drag never touches: framing a model automatically, turning to a chosen angle over time instead of snapping to it, and stepping that turn every frame.

Step 1: Something to frame #

A box, and its bounds as an Aabb3. frameBounds only needs the bounding box, not the mesh itself, which is why picking a good bounding box matters more than the shape inside it.

_bounds = Aabb3.centerAndHalfExtents(
  Vector3.zero(),
  Vector3(0.5, 1.0, 0.5),
);

Step 2: Frame it #

frameBounds moves the target to the box's centre and pulls the camera back until the box fills the view, using the bounding sphere rather than the box so the framing holds at any angle you orbit to afterwards.

context.orbit.frameBounds(_bounds);

Step 3: Swing to a new angle #

animateTo does not move the camera itself. It starts a smoothed turn that advance steps forward each frame, so the view arrives at the new yaw and pitch instead of jumping to them.

context.orbit.animateTo(yaw: context.orbit.yaw + math.pi, seconds: 1.2);

Note. A turn started by animateTo stops the moment you drag the view by hand. A hand on the pointer always outranks an animation already in flight.

Step 4: Step the turn #

Nothing in animateTo moves the camera by itself; advance is what actually turns it, a little further each frame, until the turn's own duration has passed.

@override
void update(DemoContext context, double dt) {
  context.orbit.advance(dt);
}