擬似レンダーテクスチャ。（デモ：https://dl.dropboxusercontent.com/u/56297224/UnitySumple2/offscreen%20render%28free%29/Capture%20Color/Capture%20Color.html）

GetTexture.cs

using UnityEngine;
using System.Collections;

public class GetTexture : MonoBehaviour {

	public BackgroundRenderBasic target;
	public GameObject model = null;

	void Start()
	{
		target.result = ()=>
		{
			renderer.material.mainTexture = target.screenshot;
		};
	}

	void OnGUI()
	{
		if( GUILayout.Button("camera "+ ((target.gameObject.activeSelf)?"off":"on")) )
		{
			target.gameObject.SetActive(!target.gameObject.activeSelf);
		}

		if( GUILayout.Button("model "+ ((model.activeSelf)?"hide":"show")) )
		{
			model.SetActive(!model.activeSelf);
		}

	}
}

RenderTextureFake.cs

using UnityEngine;
using System.Collections;
using System.IO;
using System;

namespace AngryChicken2D
{

	public class BackgroundRenderBasic : MonoBehaviour
	{
		public Texture2D screenshot { get; private set; }
		RenderTexture renderTexture = null;
		public Action result = null;

		[Range(1, 5)]
		public int
			textureScale = 1;
	
		void Awake()
		{
			int width = Screen.width / textureScale;
			int height = Screen.height / textureScale;
			screenshot = new Texture2D(width, height, TextureFormat.RGB24, false);
			renderTexture = new RenderTexture(width, height, 24);
			camera.targetTexture = renderTexture;
		}
	
		void OnPostRender()
		{
			Take();
		
			if (result != null)
				result();

			gameObject.SetActive(false);
		}
	
		protected void Take()
		{
			screenshot.ReadPixels(new Rect(0, 0, Screen.width, Screen.height), 0, 0);
			screenshot.Apply();
		}

		void OnDestroy()
		{
			Destroy(renderTexture);
			Destroy(screenshot);
			result = null;
		}
	}
}