Hiding certain objects from being drawn on a camera or SceneCapture2D object.

[SpaceComplexity]

Is there a way to cull certain objects from a camera's view?

[bigzer]

I would love to know the answer too.

[senress]

The engine doesn't expose any way to do this right now. The underlying renderer supports it. It's definitely a useful feature, I'll add it to our backlog of features we'd like to add. I can't promise when we will get to it though!

--
For coders out there, if you have a look at the code in FScene::UpdateSceneCaptureContents, it calls a function called CreateSceneRenderer. Inside that function you can see that it creates an FSceneView and adds it to the view family. An FSceneView has a member HiddenPrimitives which is a set of primitive IDs that the renderer should ignore when rendering the scene. If I were to implement this I'd do something like the following:

1) Add a set of UPrimitiveComponents that I want to be hidden to USceneCaptureComponent:

UPROPERTY(EditAnywhere,BlueprintReadWrite,Category=SceneCapture)
TSet<TWeakObjectPtr<UPrimitiveComponent> > HiddenComponents

2) I'd add some helper functions to USceneComponent exposed to Blueprint that help me add components and actors to it:

/** Adds the component to our list of hidden components. */
UFUNCTION(BlueprintCallable, Category="Rendering|SceneCapture")
ENGINE_API void HideComponent(UPrimitiveComponent* InComponent);

/** Adds all primitive components in the actor to our list of hidden components. */
UFUNCTION(BlueprintCallable, Category="Rendering|SceneCapture")
ENGINE_API void HideActorComponents(AActor* InComponent);

3) Modify FScene::UpdateSceneCaptureContents / FScene::CreateSceneRenderer to take my list of components and add them to the set of hidden primitives on the view:

for (auto It = HiddenComponents.CreateConstIterator(); It; ++It)
{
	// If the primitive component was destroyed, the weak pointer will return NULL.
	UPrimitiveComponent* PrimitiveComponent = It->Get();
	if (PrimitiveComponent)
	{
		View->HiddenPrimitives.Add(PrimitiveComponent->ComponentId);
	}
}

If someone here gives it a go, tests it, and it all works add a pull request and you can help us get it in more quickly!

[bigzer]

Thank you.

Is it possible to say instead of 'hide A and B and Z' to tell the engine 'render only A and B’?
In terms of performance and maintenance wouldn’t it be better?

What I'm trying to achieve here is a way to render my FPS weapon separately (so I can have a different FOV for the world scene and the weapons amongst other advatages)

Would this be a good solution or would you recommend another scheme?

[senress]

You're right, if you only wish to render a small number of objects it would be better to "whitelist" them. The renderer supports that for debugging but it's not exposed very well. E.g. we can freeze visibility for a view and move the camera around to see how well the occlusion system is working. In code look at the FrozenPrimitives set on the view state.

Adding a similar construct on the FSceneView itself would be the best solution.

[bigzer]

Thank you Nick, this sounds great!

How will shadows behave?
Say you have an object A casting a shadow on an object B. We have 2 cameras and each of them is hiding a different object (A or B). Will B still get the shadow of A?
If not is there a reasonable way to do that?

Thank for your answers they are very helpful.

[senress]

If a primitive is explicitly hidden for a view it will not cast a shadow. That can be overridden per-primitive such that they will cast a shadow even when hidden:

	/** 
	 *	If true, the primitive will cast shadows even if bHidden is true.
	 *	Controls whether the primitive should cast shadows when hidden.
	 *	This flag is only used if CastShadow is true.
	 */
	UPROPERTY(EditAnywhere, AdvancedDisplay, BlueprintReadOnly, Category=Lighting)
	uint32 bCastHiddenShadow:1;

See FPrimitiveSceneProxy::IsShadowCast for the code that decides whether a primitive casts a shadow or not.

[leucus]

ive got a question to throw on this for you guys, finally figured out how to set this capture 2d up and setup the render image, or so i thought, my problem is that my texture on my mesh is throwing a tiled version up (multiple images) is there a good tutorial somewhere on how to set this up properly, ive got an entire level thats going to rely on mirrors of different sizes ? thanks in advance for any help

[bigzer]

FYI we've exposed the 'render blacklist' feature both for blueprints and code and have sent a pull request on Github so everyone can enjoy it.

Thank you Nick

[senress]

I've integrated your pull request in to main and it will be in 4.3. Thanks for the submission bigzer!

[BrUnO XaVIeR]

Was this implemented? I can't find anything about it on 4.5.

[Chosker]

I'd also be interested in knowing

[devast3d]

Bump. Also interested in this feature.

[Joe Conley]

Just came across this thread, but it looks like this feature was implemented in 4.3. You can use it by dragging off of a Scene Capture actor or component reference in a blueprint, selecting the "Hide Actor Components" or "Hide Components" nodes, and passing a reference to the Actor or Component you want to hide in this Scene Capture:



You can also set the viewport show flags for a Scene Capture component in the advanced section of the scene capture properties:

[tardygrade]

How do you get to this advanced panel ? I don't see anything like that on my scenecapture2D component. The last thing from this screenshot I see is Max View Distance Override, and then I see Film right after that, but no advanced props.