DBuffer decals in Rift render in single eye

Development Platform & Builds XR Development
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1

Using UE 4.5 (this also happened in 4.4.3) DBuffer based decals only render in the right eye while using the Oculus Rift. Unfortunately, this makes decals unusable for VR.

18265-riftdecals.jpg
18265-riftdecals.jpg1920×1080 252 KB

As you can see in the image, the bullet hole decals are only being rendered in the right eye. The decals themselves reference a Material Instance. The Material being used by the Instance has its Material Domain set to Deferred Decal, and its Decal Blend Mode is “DBuffer Translucent Color, Normal, Roughness”. Finally, I have the appropriate rendering cvars set (r.DBuffer=1, etc.).

Is there anything I can do at my end to get these working? Not being able to use DBuffered decals at all in VR is extremely limiting.

2

Update: Still happening in UE 4.5.1.

3

Hi Gnometech,

Unfortunately DBuffer Decals and some HUD elements do not work properly with VR at the moment. This is a known issue that our developers are currently looking into. I hope to have some more info on this soon and will post back here.

Thanks,

TJ

4

Thanks for letting me know. I hope this can be fixed soon. The environment is sterile without decals.

5

I just wanted to update and let you know that this has been logged into our tracking software as JIRA #2941.

1 Like
6

Hello,

I ran into this problem as well in 4.5.1, and was able to track the issue to the DBuffer clears in FRCPassPostProcessDeferredDecals::Process in PostProcessDeferredDecals.cpp:

   SCOPED_DRAW_EVENT(RHICmdList, DBufferClear, DEC_SCENE_ITEMS);
    {
    	SetRenderTarget(RHICmdList, GSceneRenderTargets.DBufferA->GetRenderTargetItem().TargetableTexture, FTextureRHIParamRef());
    	RHICmdList.Clear(true, FLinearColor(0, 0, 0, 1), false, 0, false, 0, FIntRect());
    	SetRenderTarget(RHICmdList, GSceneRenderTargets.DBufferB->GetRenderTargetItem().TargetableTexture, FTextureRHIParamRef());
    	// todo: some hardware would like to have 0 or 1 for faster clear, we chose 128/255 to represent 0 (8 bit cannot represent 0.5f)
    	RHICmdList.Clear(true, FLinearColor(128.0f / 255.0f, 128.0f / 255.0f, 128.0f / 255.0f, 1), false, 0, false, 0, FIntRect());
    	SetRenderTarget(RHICmdList, GSceneRenderTargets.DBufferC->GetRenderTargetItem().TargetableTexture, FTextureRHIParamRef());
    	// R:roughness, G:roughness opacity
    	RHICmdList.Clear(true, FLinearColor(0, 1, 0, 1), false, 0, false, 0, FIntRect());
    }

The issue is that each of those calls to Clear() cleared the entire surface, so the right eye cleared the decals from the left eye. The solution is to add a call to SetViewport() after each call to SetRenderTarget():

 SCOPED_DRAW_EVENT(RHICmdList, DBufferClear, DEC_SCENE_ITEMS);
    {
    	SetRenderTarget(RHICmdList, GSceneRenderTargets.DBufferA->GetRenderTargetItem().TargetableTexture, FTextureRHIParamRef());
    	Context.SetViewportAndCallRHI(Context.View.ViewRect); // FIXES bug with no decals in left eye
    	RHICmdList.Clear(true, FLinearColor(0, 0, 0, 1), false, 0, false, 0, FIntRect());
    	SetRenderTarget(RHICmdList, GSceneRenderTargets.DBufferB->GetRenderTargetItem().TargetableTexture, FTextureRHIParamRef());
    	Context.SetViewportAndCallRHI(Context.View.ViewRect); // FIXES bug with no decals in left eye
    	// todo: some hardware would like to have 0 or 1 for faster clear, we chose 128/255 to represent 0 (8 bit cannot represent 0.5f)
    	RHICmdList.Clear(true, FLinearColor(128.0f / 255.0f, 128.0f / 255.0f, 128.0f / 255.0f, 1), false, 0, false, 0, FIntRect());
    	SetRenderTarget(RHICmdList, GSceneRenderTargets.DBufferC->GetRenderTargetItem().TargetableTexture, FTextureRHIParamRef());
    	Context.SetViewportAndCallRHI(Context.View.ViewRect); // FIXES bug with no decals in left eye
    	// R:roughness, G:roughness opacity
    	RHICmdList.Clear(true, FLinearColor(0, 1, 0, 1), false, 0, false, 0, FIntRect());
    }

I hope this helps,

7

Thanks , solved the issue for me :slight_smile:

8

Just posting to let you know the answer below by is the valid one.

9

Same Issue with 4.11, but seems like the code its being changed, any idea what to do? thx in advance :smiley:

10

Hi Icchansan,

This issue was reported in 2014 and was resolved in the 4.8 release. If you are seeing it now in 4.11, could you please create a new report in the Bug Report section of AnswerHub? Please include as much info as possible, including screenshots.

Thanks,

TJ