thermion-camera-input

name

thermion-camera-input

description

Position and control the camera, and add user interaction, in a Thermion scene. Covers camera lookAt (there is no setCameraPosition), lens projection (focal length) and field-of-view projections, exposure, multiple cameras, orbit and free-flight controls via ManipulatorType on ViewerWidget or DelegateInputHandler with ThermionListenerWidget, sensitivity tuning, and writing custom input handlers. Use when framing a shot, moving the camera, adding drag/scroll/zoom controls, or handling touch and mouse input. Triggers: camera, lookAt, camera position, move camera, orbit, orbit controls, free flight, first person, field of view, fov, projection, focal length, zoom, exposure, aperture, input handler, mouse, touch, scroll wheel, sensitivity, manipulator, drag rotate.

There is no setCameraPosition on the viewer. Get the active camera and aim it with lookAt — first argument is the camera's position, then an optional focus point (defaults to the origin) and up vector (defaults to +Y):

final camera = await viewer.getActiveCamera();
await camera.lookAt(Vector3(3, 3, 3), focus: Vector3(0, 0, 0));
final Vector3 pos = camera.getPosition();

The default camera sits at (0, 0, 0) looking down −Z — inside any object placed at the origin. Always lookAt from a distance after loading.

Projection

// Physical lens (default feel): focal length in mm.
await camera.setLensProjection(near: 0.1, far: 100.0, aspect: 1.0, focalLength: 28.0);

// Or an explicit field of view:
await camera.setProjectionFromVerticalFieldOfView(45.0, 0.1, 1000.0, aspect);
await camera.setProjectionFromHorizontalFieldOfView(60.0, 0.1, 1000.0, aspect);

// Exposure (aperture f-number, shutter speed seconds, sensitivity ISO):
await camera.setExposure(16.0, 1 / 125, 100.0);

After viewer.setViewport(w, h) cameras update to the new aspect ratio.

Multiple cameras

final cam2 = await viewer.createCamera();
await cam2.lookAt(Vector3(0, 10, 0), focus: Vector3(0, 0, 0));
await viewer.setActiveCamera(cam2);       // render from cam2
await viewer.destroyCamera(cam2);          // cleanup
final count = viewer.getCameraCount();

Flutter — built-in controls (ViewerWidget)

ViewerWidget(
  assetPath: 'assets/cube.glb',
  initialCameraPosition: Vector3(0, 2, 4),
  manipulatorType: ManipulatorType.ORBIT, // ORBIT | FREE_FLIGHT | NONE
);

Flutter — manual controls (ThermionListenerWidget)

Wrap ThermionWidget in a ThermionListenerWidget with a delegate input handler — this is the low-level path when you create the viewer yourself:

ThermionListenerWidget(
  inputHandler: DelegateInputHandler.fixedOrbit(
    viewer,
    minimumDistance: 0.1,     // how close the camera may zoom
    sensitivity: InputSensitivityOptions(
      scrollWheelSensitivity: 0.005,
    ),
  ),
  child: ThermionWidget(viewer: viewer),
);

// Free-flight (WASD-style) instead of orbit:
DelegateInputHandler.flight(viewer, freeLook: true)

fixedOrbit options: target (orbit center), minimumDistance, moveOnHover, sensitivity. flight options: freeLook, moveOnHover, sensitivity. Sensitivity covers touch, mouse, scroll, and keys via InputSensitivityOptions.

Custom input handling

Implement an input handler delegate to route arbitrary Flutter gestures into camera motion (or picking — see the thermion-picking-selection skill):

GestureDetector(
  onPanUpdate: (details) {
    // Convert deltas to orbit angles and call camera.lookAt yourself.
  },
  child: ThermionWidget(viewer: viewer),
)

Gotchas

• Camera motion is lookAt / setModelMatrix / setTransform(Matrix4) — not setPosition.
• lookAt positions the camera at the FIRST argument; the focus is what it looks AT. Swapping them is the classic mistake.
• +Y is up, −Z is into the screen (right-handed).
• FOV functions take degrees; setLensProjection takes millimeters.
• ViewerWidget installs its own manipulator; don't add a ThermionListenerWidget around it.

References

• references/dart-camera-projections.dart — complete pure-Dart program comparing lens and FOV projections.

Docs

• https://thermion.dev/camera-manipulation/ — orbit/free-flight/custom input