Best way to have a camera only see certain objects?

Questions & Answers
1

Layers aren’t exactly what I’m looking for in this scenario. Basically, I want two (or more) cameras to be able to move across a timeline and render objects if and only if they exist at that point in the timeline. Time travel shenanigans.

Example Timeline:

<–WWWWW-------OOOOO-------------->

As the camera moves back and forth across the timeline (via player input) it would only see the Ws when at a point when they exist. Same for the Os. Naturally, there would be more than two objects and overlaps will certainly occur.

Is there a way to, on the camera, grab a variable from the objects and only render it if that variable matches? The only solution I found was to iterate through every object and enable/disable the rendering of it depending on where the camera is and that feels really clunky when done for multiple cameras in succession.

2

As Chuckleluck wrote, you can use OnPreRender and OnPostRender. In this example, the layer of an object is switched so it isn’t rendered by this particular camera.

using UnityEngine;
using System.Collections;

public class SwitchLayer : MonoBehaviour {

	public GameObject go;
    public string layerName_0 = "MyLayer0";//the layer that is not rendered by this camera
    public string layerName_0 = "MyLayer1";//The object's normal layer

	void OnPreRender() {
		if(go== null) {
			return;
		}

		go.layer = LayerMask.NameToLayer("MyLayer0");
	}

	void OnPostCull() {
		if(go== null) {
			return;
		}
		
		go.layer = LayerMask.NameToLayer("MyLayer1");
	}
}