TypeScript: Camera.rotationQuaternion should allow null type

[nsxdavid]

Description

The TypeScript type definition for Camera.rotationQuaternion (specifically in TargetCamera and its children) is incorrectly defined as non-nullable:

rotationQuaternion: Quaternion;

However, setting this property to null is documented, intentional behavior. According to Babylon.js patterns, setting rotationQuaternion = null is the standard way to disable quaternion-based rotation and allow the camera to use Euler angles (rotation property) instead.

Current Behavior

TypeScript incorrectly rejects this valid runtime code:

camera.rotationQuaternion = null;  // Type error: Type 'null' is not assignable to type 'Quaternion'

Expected Behavior

The type definition should allow null:

rotationQuaternion: Quaternion | null;

Current Workaround

(camera as {rotationQuaternion: Quaternion | null}).rotationQuaternion = null;

Impact

• This is a type-only change that better reflects actual runtime behavior
• May require users to add null checks when accessing the property, which is appropriate since it can actually be null at runtime
• Improves type safety by preventing assumptions that this property is always defined

Version

• Babylon.js: 8.26.0 (but appears present in latest versions as well)

Additional Context

This pattern (setting rotationQuaternion = null) is used throughout Babylon.js examples and is the recommended approach when you want the camera rig to control all orientation via parent transforms without local camera rotation.