GradientBackground.cs

// GradientBackground.cs
// By Eric Haines (Eric5h5)
// From http://wiki.unity3d.com/index.php/CameraGradientBackground
// Slightly modified by Roidz and Deozaan

using UnityEngine;

public class GradientBackground : MonoBehaviour {

    public Color topColor = Color.blue;
    public Color bottomColor = Color.white;
    public int gradientLayer = 7;

    void Awake() {
        gradientLayer = Mathf.Clamp(gradientLayer, 0, 31);
        if (!camera) {
            Debug.LogError("Must attach GradientBackground script to the camera");
            return;
        }

        Transform container = new GameObject("Gradient").transform;
        container.parent = transform;

        camera.clearFlags = CameraClearFlags.Depth;
        camera.cullingMask = camera.cullingMask & ~(1 << gradientLayer);
        Camera gradientCam = new GameObject("Gradient Cam", typeof(Camera)).camera;
        gradientCam.depth = camera.depth - 1;
        gradientCam.cullingMask = 1 << gradientLayer;
        gradientCam.transform.parent = container;

        Mesh mesh = new Mesh();
        mesh.vertices = new Vector3[4] {
            new Vector3(-100f, .577f, 1f),
            new Vector3(100f, .577f, 1f),
            new Vector3(-100f, -.577f, 1f),
            new Vector3(100f, -.577f, 1f)
        };

        mesh.colors = new Color[4] { topColor, topColor, bottomColor, bottomColor };
        mesh.triangles = new int[6] { 0, 1, 2, 1, 3, 2 };

        Material mat = new Material("Shader \"Vertex Color Only\"{Subshader{BindChannels{Bind \"vertex\", vertex Bind \"color\", color}Pass{}}}");
        GameObject gradientPlane = new GameObject("Gradient Plane", typeof(MeshFilter), typeof(MeshRenderer));

        ((MeshFilter)gradientPlane.GetComponent(typeof(MeshFilter))).mesh = mesh;
        gradientPlane.renderer.material = mat;
        gradientPlane.layer = gradientLayer;
        gradientPlane.transform.parent = container;
    }
}