LightmapPixelPicker.cs

using UnityEngine;
using System.Collections;

public class LightmapPixelPicker : MonoBehaviour {

	public Color surfaceColor;
	public float brightness1; // http://stackoverflow.com/questions/596216/formula-to-determine-brightness-of-rgb-color 
	public float brightness2; // http://www.nbdtech.com/Blog/archive/2008/04/27/Calculating-the-Perceived-Brightness-of-a-Color.aspx
	public LayerMask layerMask;

	void Update()
	{
		Raycast();

		// BRIGHTNESS APPROX
		brightness1 = (surfaceColor.r + surfaceColor.r + surfaceColor.b + surfaceColor.g + surfaceColor.g + surfaceColor.g) / 6;

		// BRIGHTNESS
		brightness2 = Mathf.Sqrt((surfaceColor.r * surfaceColor.r * 0.2126f + surfaceColor.g * surfaceColor.g * 0.7152f + surfaceColor.b * surfaceColor.b * 0.0722f));
	}

	void OnGUI()
	{
		GUILayout.BeginArea(new Rect(10f, 10f, Screen.width, Screen.height));

		GUILayout.Label("R = " + string.Format("{0:0.00}", surfaceColor.r));
		GUILayout.Label("G = " + string.Format("{0:0.00}", surfaceColor.g));
		GUILayout.Label("B = " + string.Format("{0:0.00}", surfaceColor.b));

		GUILayout.Label("Brightness Approx = " + string.Format("{0:0.00}", brightness1));
		GUILayout.Label("Brightness = " + string.Format("{0:0.00}", brightness2));

		GUILayout.EndArea();
	}

	void Raycast()
	{
		// RAY TO PLAYER'S FEET
		Ray ray = new Ray(transform.position, -Vector3.up);
		Debug.DrawRay(ray.origin, ray.direction * 5f, Color.magenta);

		RaycastHit hitInfo;

		if (Physics.Raycast(ray, out hitInfo, 5f, layerMask))
		{
			// GET RENDERER OF OBJECT HIT
			Renderer hitRenderer = hitInfo.collider.GetComponent<Renderer>();

			// GET LIGHTMAP APPLIED TO OBJECT
			LightmapData lightmapData = LightmapSettings.lightmaps[hitRenderer.lightmapIndex];

			// STORE LIGHTMAP TEXTURE
			Texture2D lightmapTex = lightmapData.lightmapColor;

			// GET LIGHTMAP COORDINATE WHERE RAYCAST HITS
			Vector2 pixelUV = hitInfo.lightmapCoord;

			// GET COLOR AT THE LIGHTMAP COORDINATE
			Color surfaceColor = lightmapTex.GetPixelBilinear(pixelUV.x, pixelUV.y);

			// APPLY
			this.surfaceColor = surfaceColor;
		}
	}

}

Hi! What you're doing here is amazing and I have been trying to get the lightning of a texture for a while with different approaches without success. But for some reason this code doesn't work for me. My hitRenderer.lightmapIndex is -1 and LightmapSettings.lightmaps is an array of length 1 that starts at 0 and cannot be accesed at -1. Do you know what could be the problem? Thank you :)