Decals and oculus rift problem

Hello robi2005,

After doing a bit of digging I found that this is a known issue (UE-11849) and that it has been resolved internally. This solution will be available in a later release of the engine. I have provided two options below that may be able to resolve your issue. The first is a bit of code that a developer had changed to solve a similar issue. The other is the commit that was used for UE-11849. I hope that this helps.

In "SetupPrePassView" in "DeferredShadingRenderer.cpp"

change this:

 RHICmdList.SetScissorRect(true, ViewRect.Min.X, ViewRect.Min.Y, ViewRect.Max.X, ViewRect.Max.Y);

  

to this:

 RHICmdList.SetScissorRect(false, 0, 0, 0, 0);

The Commit:

https://github.com/EpicGames/UnrealEngine/commit/10f7131b928cb855b674eba17bfac3f249c26394

Make it a great day

Howdy ciddi3d,

Than you again for your bug report. I have entered the bug into our database so that it may be further investigated.

Thanks and have a great day!

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,

Curtis