Update README.md

README.md

@@ -69,7 +69,7 @@ You can use the scripts inside `colmap_runner` to generate camera parameters fro
     * Split distortion-free images and `kai_cameras_normalized.json` according to your need.
 
 ## Visualize cameras in 3D
-Check `camera_visualizer/visualize_cameras.py` for visualizing cameras in 3D. It creates an interactive viewer for you to inspect whether your cameras have been normalized to be compatible with this codebase. Below is a screenshot of the viewer: green cameras are used for training, blue ones are for testing, while yellow ones denote a novel camera path to be synthesized.
+Check `camera_visualizer/visualize_cameras.py` for visualizing cameras in 3D. It creates an interactive viewer for you to inspect whether your cameras have been normalized to be compatible with this codebase. Below is a screenshot of the viewer: green cameras are used for training, blue ones are for testing, while yellow ones denote a novel camera path to be synthesized; red sphere is the unit sphere.
 
 <!-- ![](camera_visualizer/screenshot_lowres.png) -->
 <img src="camera_visualizer/screenshot_lowres.png" width="280">