Finding the Right Timing for Transitioning:
In the provided example, mouse events are utilized to adjust the camera's field of view in the onDocumentMouseWheel function. Decreasing the fov results in a "Zoom In" effect, while increasing it leads to a "Zoom Out". By monitoring the fov value and detecting when it reaches minimum or maximum thresholds, you can then initiate the transition to a new scene.
Selecting the Transition Destination:
The next step involves deciding which new scene to transition to. One approach is to use a hotspot-like system where a ray is cast from the camera to check for collisions with specific objects (such as a strategically placed THREE.Sphere). If simplicity is preferred, you can stick to the 6 cardinal directions and continue using the mouse control from the example.
Camera movement is controlled in the onDocumentMouseMove function by adjusting the lat and lon variables (presumably in degrees). You can implement logic to distinguish between different viewing angles, such as checking if the camera is looking up, down, or at a side based on the values of lat and lon.
Once you reach the maximum zoom level, the direction in which you are looking will dictate the destination scene for the transition.
Executing the Transition:
There are numerous ways to handle the transition process. Options include swapping out textures on objects, switching to a completely new THREE.Scene, adjusting the camera position, modifying lighting effects, or applying post-processing effects for a smoother transition. The style of transition is entirely customizable and depends on your design preferences.
Responding to @Marquizzo's Input:
The suggestion regarding lighting is aimed at enhancing the transition effect. In the example, a light source is not utilized due to the material being a MeshBasicMaterial. Instead of changing scene.background, the texture is applied to an inverted sphere. Alternative methods, such as CSS transitions, can be explored if adjusting the brightness of the texture is challenging.
To demonstrate a fading effect, I have included additional code in the example that alters the color of a material to create a fading in/out effect. This showcases how the transition can be customized through various techniques, providing flexibility for creative decision-making.