Resolved RenderTexture not clearing buffer on Android

I have a system where there's no main camera. Instead, each layer of the game (tiles, characters, huds, etc) has its own camera and is rendering to a RenderTexture. Then I use the OnGUI method to draw each layer with DrawTexture one on top of each other. It works fine when building for pc, but the android build refuses to clear the buffer each frame, resulting in the attached image.

Here is the relevant code:

Setting up the Camera and RenderTexture:

Code (CSharp):

1. private RenderTexture BuildRenderTexture() {
2.     RenderTexture = new RenderTexture(
3.         GameProperties.RenderDimensionsWidth,
4.         GameProperties.RenderDimensionsHeight,
5.         24,
6.         RenderTextureFormat.Default
7.     ) {filterMode = FilterMode.Point};
8.     RenderTexture.Create();
9.  
10.     Camera = gameObject.AddComponent<UnityEngine.Camera>();
11.     Camera.clearFlags = CameraClearFlags.Color;
12.     Camera.backgroundColor = new Color(0, 0, 0, 0);
13.     Camera.cullingMask = -1;
14.     Camera.orthographic = true;
15.     Camera.nearClipPlane = 0f;
16.     Camera.farClipPlane = GameProperties.MapLayerDepth;
17.     Camera.depth = 1f;
18.     Camera.targetDisplay = 0;
19.     Camera.aspect = GameProperties.AspectRatio;
20.     Camera.orthographicSize = GameProperties.DefaultCameraSize;
21.     Camera.targetTexture = RenderTexture;
22.  
23.     VisibleTileCount = new Vector2(
24.         Camera.orthographicSize * 2f * Camera.aspect,
25.         Camera.orthographicSize * 2f
26.     );
27.  
28.     return RenderTexture;
29. }

Using OnGUI to render each RenderTexture to the screen:

Code (CSharp):

1. private void OnGUI() {
2.     RenderBackdrop();
3.  
4.     GUI.BeginGroup(new Rect(0, 0, Screen.width, Screen.height));
5.     foreach (KeyValuePair<string, MapCameraLayer> mapCameraLayer in _mapCameraLayers) {
6.         RenderLayer(mapCameraLayer.Value.RenderTexture);
7.     }
8.  
9.     foreach (KeyValuePair<string, RenderTexture> uiCameraLayer in _uiCameraLayers) {
10.         RenderLayer(uiCameraLayer.Value);
11.     }
12.  
13.     GUI.EndGroup();
14. }
15.  
16. private void RenderBackdrop() {
17.     Graphics.DrawTexture(new Rect(0, 0, Screen.width, Screen.height), _backdrop);
18. }
19.  
20. private void RenderLayer(RenderTexture renderTexture) {
21.     Rect screenRenderRect = GetRenderRect();
22.     Graphics.DrawTexture(screenRenderRect, renderTexture);
23. }

I have no idea if this issue is a problem with the Camera, the RenderTexture, the Android Player Build Settings, or with Unity itself.

 

_backdrop is created as:

Code (CSharp):

1. private void BuildBackdropTexture() {
2.     Color32[] backdropColor = {Color.black};
3.     _backdrop = new Texture2D(1, 1);
4.     _backdrop.SetPixels32(backdropColor);
5.     _backdrop.Apply();
6. }

It looks like this could just be replaced with

GL.Clear(true, true, Color.black)

I added the clear command as the first line in OnGUI, and this doesn't resolve the problem. I also added a main camera (which OnGUI just draws over the top of anyway) and this also didnt resolve the problem.





To be more clear about what's going on, let me show in images.

The scene in 3d looks like this:



You can see two cameras: both facing in the same direction and only capturing whats inside the white box in front of it. One captures the bit with the room and the door. The other captures the bit with the player and the tables. Both cameras have their ClearFlags set to Color (per the construction code I posted in the first post of this thread).

The camera settings are:


The cameras pick up the following:

First one


Second one




So we first draw a black texture (or GL.Clear. or both.) to the whole screen. Then render the first RenderTexture(the door/room) on top of that backdrop, and then render the second RenderTexture (the player and tables) on top of those. To result in:



And it works perfectly, except on Android, where the RenderTexture's buffer isnt being cleared.


This is a critical bug for my asset that's currently available on the store, and I've tried everything I can think of, and I'm getting the same result every time.

 

I finally figured out the problem and I'm posting here in case anyone else runs into it. I was using

Graphics.Blit(RenderTexture, RenderTexture, _material);

in

OnPostRender()

. I changed it so that I am now applying the material in

Graphics.DrawTexture

and that works.