## ADDED Requirements

### Requirement: Camera supports orbit, pan, and zoom interaction

The system SHALL provide a turntable-style orbit camera controlled by mouse input within the Viewport panel. Left-drag orbits around a focal point, middle-drag or shift+left-drag pans, and scroll-wheel zooms.

#### Scenario: Orbit the camera
- **WHEN** the user holds the left mouse button and drags within the Viewport panel
- **THEN** the camera orbits around the focal point
- **AND** the view updates in real-time

#### Scenario: Pan the camera
- **WHEN** the user holds the middle mouse button (or shift+left button) and drags within the Viewport panel
- **THEN** the camera pans horizontally and vertically relative to the view plane
- **AND** the focal point moves with the camera

#### Scenario: Zoom the camera
- **WHEN** the user scrolls the mouse wheel within the Viewport panel
- **THEN** the camera moves closer to or farther from the focal point
- **AND** the zoom is proportional to the current distance from the focal point

### Requirement: Camera computes view and projection matrices

The system SHALL compute a view matrix from the camera's eye position, focal point, and up vector, and a perspective projection matrix from the field of view, aspect ratio, and near/far clip planes.

#### Scenario: View matrix from camera parameters
- **WHEN** the camera parameters (eye, focal point, up) are set or updated
- **THEN** the system computes a `lookAt` view matrix

#### Scenario: Projection matrix matches viewport aspect ratio
- **WHEN** the FBO dimensions change
- **THEN** the projection matrix is recomputed with the updated aspect ratio

### Requirement: Mouse input is captured only when the viewport is hovered

The system SHALL capture mouse input for camera control only when the ImGui Viewport window is hovered. Mouse events outside the viewport SHALL NOT affect the camera.

#### Scenario: Mouse input captured in viewport
- **WHEN** the mouse cursor is over the Viewport panel and the user interacts
- **THEN** the camera responds to the input

#### Scenario: Mouse input ignored outside viewport
- **WHEN** the mouse cursor is outside the Viewport panel
- **THEN** camera input is not processed

### Requirement: Camera frames the scene automatically

The system SHALL compute a default camera position that frames the bounding box of the scene when a stage is first loaded.

#### Scenario: Camera frames scene on stage load
- **WHEN** a new USD stage is opened
- **THEN** the camera position and focal point are set so the entire scene bounding box is visible
- **AND** the camera distance is adjusted based on the scene size
