Rendering Camera to PNG produces completely grey image.

Questions & Answers
1

The following Behaviour is attached to a new GameObject programatically, and when it’s done it doesn’t output a rendered image from the Camera, rather a completely grey image. What have a I done wrong or overlooked?

using UnityEngine;

namespace Cartographer
{

    class MapCameraBehaviour : MonoBehaviour
    {

        private int size = 1000;
        private Camera camera;
        private RenderTexture renderTexture;
        private Texture2D texture;
        private bool render = false;
        private int renderFrameDelay = 0;
        private bool renderNow = false;

        void Log(string message)
        {
            //some logging code
        }

        void Awake()
        {

            Log("Awake()");

            camera = GetComponent<Camera>();
            if (camera == null)
            {
                camera = gameObject.AddComponent<Camera>();
                camera.nearClipPlane = 0.1f;
                camera.farClipPlane = 2000f;
                camera.renderingPath = RenderingPath.Forward;
                camera.depth = 100;
                camera.transform.position = new Vector3(0.0f, 100.0f, 0.0f);
            }
            else
            {
                Log("Existing camera.");
            }
            if (camera != null)
            {
                Log("Camera found.");
                renderTexture = new RenderTexture(size, size, 0);
                texture = new Texture2D(renderTexture.width, renderTexture.height, TextureFormat.ARGB32, false);
                camera.targetTexture = renderTexture;
                RenderTexture.active = renderTexture;
                render = true;
                renderFrameDelay = 100;
                renderNow = false;
            }
            else
            {
                Log("Camera not found.");
            }

        }

        void Update()
        {
            if (render)
            {
                if (renderFrameDelay <= 0)
                {
                    render = false;
                    renderNow = true;
                    QualitySettings.antiAliasing = 0;
                    camera.Render();
                }
                else
                {
                    renderFrameDelay--;
                }
            }
        }

        void OnPostRender()
        {
            if (renderNow == true)
            {

                renderNow = false;

                Log("OnPostRender()");

                texture.ReadPixels(new Rect(0.0f, 0.0f, renderTexture.width, renderTexture.height), 0, 0);

                byte[] bytes = texture.EncodeToPNG();
                System.IO.File.WriteAllBytes(Application.dataPath + "/texture.png", bytes);

                camera.targetTexture = null;
                RenderTexture.active = null;

                DestroyImmediate(texture);
                DestroyImmediate(renderTexture);

                Log("Done.");

            }
        }

    }

}
2

Have you tried to apply the texture after reading the pixels?

texture.ReadPixels(new Rect(0.0f, 0.0f, renderTexture.width, renderTexture.height), 0, 0);
texture.Apply();

Also make sure the texture is Read/Write enabled.