How to set up a camera so that it doesn't clear the color buffer?

Hello,

I'm using Unity 2019.3.3f and the latest Universal RP 7.2.1. I have a camera stack set up - the base camera renders my level (layer Default), and the overlay camera renders the "field of view" mesh that I'm generating on the fly (it's on a separate layer called "Mask".)

Now when I use the stack and combine the outputs of those two cameras, it works correctly, i.e. I can see the rendered field of view mesh overlaid on the base camera's output. But my aim is to have the field of view to unveil the map, so all areas that have already been visited by the player should be visible, and the remaining ones not.

I think the problem is that the overlay camera clears its color buffer everytime it renders, because it only renders the current "state" of the field of view mesh.

How do I set up the stack so that I can achieve what I'm looking for?

If you need any more information, please let me know.

Thank you,
Patryk

 

I decided to try a different setup and show you guys the approach that I'm currently taking.

Here's my minimap camera. It basically follows the player (that's why it has a script attached to it, background type is set to 'Uninitialized'):


Here's the renderer configuration that it uses:


And now let's run the game and see what happens. As you can see, it correctly renders the view mesh. I know that it might look bad in the picture, but believe that it's the expected result:


Now let's move to the right so that the field of view mesh can expand:


As you can see, the little fragment at the very start is now gone and the current state of the field view mesh is now rendered to the texture. What I would like to achieve is this (this picture's been done in Photoshop):


The above effect should be easily achieved if the render texture didn't clear every frame, I believe.

Do you think my setup is wrong somewhere, something is missing, or is that a bug in Unity? Also, if you have a different idea on how to do that "uncovering map" effect, I'm open to learn about them.

Thank you,
Patryk

 

Another observation is that if I set the camera's solid color to some value and then set it back to Uninitialized, I can still see that color in the render texture.

Seriously, am I missing some really obvious stuff here or is it clearly a bug?

 

Sure, how do I do that? And what exactly is the problem?

 

@phil_lira I think that you only want to fix the problem with the editor still showing the camera color in the preview, but the problem is (I think) in the render texture being cleared every frame, even though I don't really want to do that, because I explicitly set 'Background Type' to 'Uninitialized'.

 

Perfect, let me report it for you!

 

@phil_lira The tracking link is here: http://fogbugz.unity3d.com/default.asp?1224369_7mrk4u7mtf10ar0u

Thanks,
Patryk

 

@phil_lira Do you happen to know if there's any progress on this issue? Do you guys need more information from me?

Regards,
Patryk

 

@phil_lira Could you tell me if you guys fixed the bug, please?

 

@phil_lira Sorry for bugging you guys, but I'm just curious whether there's any progress on this issue. If it's fixed in whichever 2020 version, it's fine, I can upgrade.

 

@Shaunyowns Perfect, I'm waiting for your reply.

 

@Shaunyowns, any news?

 

@Shaunyowns Thank you! Please get back to me as soon as possible, I'd really love to have it resolved. I don't mind upgrading to a newer version as long as the issue's gone.

 

I was also curious about this one, and I made attempts to capture the screen buffer using a blit to a RenderTexture at the end of the render pipeline. I planned to blit the texture at the start of the next frame, as to simulate having Clear Flags: Don't Clear (or what Background Type: Uninitialized could be). I was able to achieve this in a couple of different ways, but it felt like a mess.

But in the process, I discovered an interesting solution.

If you use the Blit/pass scripts from Universal Rendering Examples, you can set up a blit feature in your renderer. If you specify a material using the Sprites/Default shader, Event: Before Rendering Prepasses, Destination: Color, it will cause it to behave as if it has Clear Flags: Don't Clear.

I have no clue why this works, but it really seems to do the trick.

 

Wow, cool! I'll check it out soon

 

I am using Unity 2019.4.5f1 LTS version.
And I currently have the same problem, camera keeps clear color buffer with background type = "Uninitialized".
Hopes this issue get fixed ASAP.
I can imagine many features need "UNINITIALIZED" / "DON'T CLEAR" background clear type.

 

Just in case anyone is interested, the bug is in the issue tracker here:
https://issuetracker.unity3d.com/is...oes-not-match-between-the-build-and-game-view
If possible, please upvote so that it gets resolved faster (hopefully).

 

Problem still exists. (Tested URP 7.5.2 and 10.2.2)
([Background Type] choose [Uninitialized])Editor show normaly, but show solid color when pack APK and running in real android phone.

 

Any news on this? I tested it on Unity 2020.1.3f1 URP 8.2 and the buffer keeps clearing every frame even when set to Uninitialized @Jebtor @pateman

 

Hi,
I'm still seeing this bug in both URP 8.3.1 (Unity 2020.1.17f1) and URP 10.2.2 (Unity 2020.2.2f1) when running on iOS.

 

@Jebtor URP multiple cameras still broken on iOS. Tried on URP 10 and 11. Submitted a new issue here: http://fogbugz.unity3d.com/default.asp?1314197_3aou5ta6k1ldbqtc

 

I can also confirm that this is broken on iOS.

 

The issue also occurs on Android while it works fine in editor (Unity 2020.2.1f1, URP 10.2.2).

 

Same. It works in editor, but not when packaged for iOS.

 

@rjonaitis But overlay camera do not let to set viewportRect. Is there way to render with overlay camera only on part of base camera viewport?

 

Also, overlay cameras can't render to a render texture!

Have the same problem. On IOS and Android "Uninitialized" background type just doesn't work, looks like it switches to "solid color". In the editor everything is perfect;

"Uninitialized" or "don't clear" features are great and this is awful we can't use it on Mobiles....

Tested on URP 10.3.1 with Unity 2020.2.6

 

Since "Uninitialized" is utterly useless since we always want the exact same behavior on any platform. Can you please add another option which is true Don't Clear flag. Don't Clear flag worked perfectly on the Standard renderer (non URP), its very useful when using it for masking, drawing and similar, since it doesn't use Texture2D.Apply or any pixel manipulations.
Don't get me started on Compute shaders and their shoot and miss compatibility with various devices, Graphics Api, and plafroms.

 

Any news on this? the developers said that it was fixed but it is not

 

Can you guys re-add the ''don't clear flags" to the Camera? I can't understand why such a valuable feature was removed

 

Just wanted to mention that I had a fog of war feature which used the "dont clear" option to keep the previously discovered areas revealed, but due to the fact that my game is for mobile I switched to URP for superior framerate, however, I cannot achieve the fog of war effect anymore.
Would love to know how I can write my own rendering script to simulate the don't clear effect that is available in the standard render pipeline.

 

Hello. How can I solve this in hdrp camera?

 

Same on some android models, 2021.1.23.

 

Hi, thank you for this idea. I'm having problems with camera clearing, and this is actually what I need, just done in a different fashion. My question is though - how can I use this with UI Raw Image component? When I preview the material, I can see it indeed does have the don't clear behavior, although I've been unable to project this material onto Raw Image component.

 

@Jonas-Mortensen can you explain how the KeepFrameFeature works when it comes to background colors? The example is a mostly empty scene with particles and a black background. Changing the Main Camera to use a Solid background doesn't have any effect and I don't understand where in the script or the shader the background is set.

I tried changing some of the colors in the shadergraph and in the code here:

Code (CSharp):

1.    public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData renderingData)
2.     {
3.         m_OldFrameHandle.Init("_OldFrameRenderTarget");
4.         m_DrawOldFame.ConfigureClear(ClearFlag.None, Color.red);
5.  
6.         m_CopyFrame.Setup(renderer.cameraColorTarget, m_OldFrameHandle);
7.         renderer.EnqueuePass(m_CopyFrame);
8.  
9.         m_DrawOldFame.Setup(settings.displayMaterial, m_OldFrameHandle, String.IsNullOrEmpty(settings.textureName) ? "_FrameCopyTex" : settings.textureName);
10.         renderer.EnqueuePass(m_DrawOldFame);
11.     }

Nothing seems to affect the background. Adding a background quad changes the background, but ruins the effect.

 

May I ask what the “Compatibility Intermediate Texture” option does, it is not selected,keep Frame not working

 

To answer my own question, I did get this to sort of work by making the background quad a transparent material and then playing with Additive, Multiply, etc. settings. It's not the same as my old project using the "Don't Clear" method, but it works. It is nice that this will be compatible across platforms and different computers. That was a real limitation with my old app, it would work on some machines but not others.

 

Still having this issue on 2020.3.25f1 building for android, Trying to find a way to render to a texture and not clear the color buffer each frame. I am looking at the camera stacking approach but I do not think that suites my needs, its getting the camera size from the viewport I cannot set it to custom dimensions. Any tips, updates, or alternative methods would be appreciated.