How-To: Live Render Target Preview

Goal: replace the static background with a live-rendered 3D scene - your character rotating on a stand, or a camera flyover - captured by a SceneCapture2D into a render target the widget displays.

Prerequisites
Quick Start is done. For a character showcase you also need How-To: Showcase the Player's Character (the stand and the director). You need a small dedicated showcase level.

1. Create the render target and capture

In the Content Browser: right-click -> Materials & Textures... -> Render Target, name it RT_Showcase, set its size (1920x1080 is plenty). In your showcase level, place a Scene Capture 2D actor framed on the stand, set its Texture Target to RT_Showcase, and keep Capture Every Frame enabled.

Verify
Double-click RT_Showcase while the showcase level is open: it shows the captured view live.

2. Enable live preview in Project Settings

In Project Settings -> Crimson -> Crimson Loading Screen -> Cinematic Preview, tick Use Live Preview and set Showcase Render Target to RT_Showcase (the field only unlocks once the checkbox is on).

Screenshot pendingImages/CrimsonLoadingScreen/howto-livepreview-settings.png
Project Settings -> Crimson -> Crimson Loading Screen -> Cinematic Preview: Use Live Preview ticked, Showcase Render Target = RT_Showcase.
Live preview keeps the world rendering
Normally the manager disables world rendering during loading to give the GPU to streaming. With bUseLivePreview on, world rendering stays enabled so the capture keeps updating - that costs GPU during loads. Keep the showcase scene lightweight. Get Showcase Render Target returns null whenever bUseLivePreview is off, even with a render target assigned.
Verify
In PIE, Get Showcase Render Target (pure node) returns a valid object.

3. Keep the showcase alive during the load

A non-seamless travel destroys the entire current world - including your capture. The capture must live in a world that survives the load. Two proven setups:

ApproachHowBest for
Seamless travel transition mapGameMode: bUseSeamlessTravel = true; set the showcase level as the transition map (below). The showcase IS the world while the destination loads.Online multiplayer; standalone games wanting a full 3D interlude
Always-loaded streaming sublevelAdd the showcase as a sublevel of your persistent level, set Always Loaded. Zone swaps stream in/out around it.Games already built on level streaming (no full LoadMap)
ini
; Config/DefaultEngine.ini - the seamless-travel transition map
[/Script/EngineSettings.GameMapsSettings]
TransitionMap=/Game/LoadingScreen/Maps/ShowcaseMap.ShowcaseMap
cpp
// MyGameMode.cpp constructor
AMyGameMode::AMyGameMode()
{
    bUseSeamlessTravel = true;
}
Seamless travel in Blueprint
In your GameMode Blueprint, tick Use Seamless Travel in Class Defaults. The transition map is set in Project Settings -> Maps & Modes -> Transition Map (same value as the ini above).
Verify
During a travel the render target keeps animating (open it in the asset editor while PIE runs, or check the widget in step 4).

4. Display the render target in the widget

Make one base material M_ShowcaseBackground: a Texture Sample Parameter 2D named RenderTarget into Emissive Color, Material Domain = User Interface. The widget wraps it in a dynamic instance and plugs in the live render target - falling back to the static background when live preview is off.

Screenshot pendingImages/CrimsonLoadingScreen/howto-livepreview-widget-bp.png
Event Construct -> Get CrimsonLoadingScreenManager -> Get Showcase Render Target -> Is Valid? Valid: Create Dynamic Material Instance (Parent = M_ShowcaseBackground) -> Set Texture Parameter Value (Name = RenderTarget) -> Set Brush from Material (BackgroundImage). Not valid: fall back to Get Current Background.
Verify
Travel with seamless travel on: the loading screen shows the live showcase scene; the director (from the character-showcase page) dresses the stand. A black image usually means the capture's world was destroyed (step 3) or Capture Every Frame is off.

See also

  • How-To: Showcase the Player's Character - the stand, the provider, and the director.
  • Concept: The Cinematic Preview Pipeline - how the pieces talk to each other and when.