<aside> ℹ️ FStaticMeshSceneProxy::DrawStaticElements

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In this part, we are talking about this step:

If you have forgotten the previous brief discussion, please click here.

The Necessity of Updates

<aside> ❓ Do we need to do this every frame?

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No, we can cache the mesh batch at the beginning or when anything changes.

Since we are dealing with a static mesh, the cube's vertices will not change, and the static mesh component is not movable, so it cannot move.

It means at least in our test case, the mesh batch is always the same.

Timing

<aside> ℹ️ FScene::UpdateAllPrimitiveSceneInfos

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So, what is that timing? It is **FScene**::UpdateAllPrimitiveSceneInfos .

I will give you a image to let you know where it is:

This image shows:

• UpdateAllPrimitiveSceneInfos runs in the render thread, not the game thread.
• UpdateAllPrimitiveSceneInfos runs before actor ticks.
• The render thread does not have its own loop. Instead, the game thread sends the render commands to the render thread to drive the rendering.
• The render thread renders only when we need to redraw the viewport. For example, if you put the Unreal Engine editor into the background, the redraw may be skipped. However, scene primitive updating is not affected by this.