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Deproject SceneCaptureComponent2D

I currently have SceneCaptureComponent2D rendering to a texture that I'm using in a UMG widget. I want to deproject mouse clicks on that UMG widget to the 3D space in front of the SceneCaptureComponent2D. I've dug around the source to see if there's anything that I can use, but I couldn't quite find anything useful. And, unfortunately, I'm still trying to wrap my head around the math needed to make it work.

Any suggestions?

Thanks, Zach

Product Version: UE 4.11
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asked Apr 15 '16 at 04:23 AM in C++ Programming

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1 answer: sort voted first

Answering my own question. This is what I did. (It involves editing UE4 source.)

First, I added two variables to USceneCaptureComponent.

     FIntRect ViewRect;
     FMatrix InvViewProjectionMatrix;

Then I populate those two variables at the end of FScene::CreateSceneRenderer (in SceneCaptureRendering.cpp)

 // Copy the data needed to do deprojection.
     SceneCaptureComponent->ViewRect = View->ViewRect;
     SceneCaptureComponent->InvViewProjectionMatrix = View->InvViewProjectionMatrix;
     return FSceneRenderer::CreateSceneRenderer(&ViewFamily, NULL);

With that in place, I can use the above and take the screen position of the click event (or whatever) and call FSceneView::DeprojectScreenToWorld.

 bool ADeprojectTest::Deproject(const FVector2D& ScreenPosition, FVector& Origin, FVector& Direction)
     if (SceneCaptureComponent)
         FSceneView::DeprojectScreenToWorld(ScreenPosition, SceneCaptureComponent->ViewRect, SceneCaptureComponent->InvViewProjectionMatrix, Origin, Direction);
         return true;
     return false;

That's it. It should return an origin and direction normal for your tracing needs.

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answered Apr 19 '16 at 02:52 AM

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avatar image antoinegloum May 08 '17 at 01:58 PM

It seems that InvViewProjectionMatrix is not in FSceneView anymore. Have you found a solution for Unreal 4.15 ?

avatar image antoinegloum May 08 '17 at 03:47 PM

I got it from View->ViewMatrices->GetInvViewProjectionMatrix(), but it seems broken.

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