camera.fov is not a function

The error message "camera.fov is not a function" typically means that you are trying to use the `fov` function on an object that does not have it defined. In most cases, `fov` is a property rather than a function.

To fix this error, you can check if the object indeed has a `fov` property, and use it accordingly. Here's an example in JavaScript:

if (camera.hasOwnProperty('fov')) {
  // Use the camera's fov property
  var cameraFov = camera.fov;
  // Rest of your code using cameraFov
} else {
  // Handle the case when the camera does not have a fov property
  console.error("Camera does not have a fov property");
}

Make sure to replace `camera` with the actual name of your camera object.