Visual popping and incorrect layering occur when the bounding box center of a mesh passes the calculated depth of another during camera movement. Unity sorts transparent objects from back-to-front based on these specific center points.

To resolve these sorting artifacts, follow these steps: 1. Select your material in the Inspector and locate the Render Face or Cull Mode setting. 2. Change this from Both to Front or Back to prevent the engine from sorting internal faces against external ones on the same object. 3. For large or concave geometry, enable Depth Write on your transparent material. In the Universal Render Pipeline, this is located under Surface Options > Depth Write. Ensure Depth Priming Mode is enabled in your URP Asset to support this. 4. Split your mesh into smaller sub-meshes within your modeling software. This creates multiple bounding box center points, allowing the engine to sort segments of the model more accurately relative to the camera distance. 5. Navigate to Project Settings > Graphics and ensure the Transparency Sort Mode is set to Perspective for 3D environments.

Additional Tips:

• Use Sorting Priority on the MeshRenderer to manually force specific objects to render above others regardless of their bounding box center.
• Consider using Alpha Clipping if the edges of your transparency do not require soft blending, as this allows the mesh to utilize the opaque Z-buffer for perfect depth sorting.
• For intricate models like hair or foliage, a custom shader with a Depth Prepass can alleviate many sorting issues without splitting the mesh.