Unreal筆記-禁止Actor或Component進行視錐剔除(frustum-culling)(Render)

自定義UPrimitiveComponent時，通過PDI進行繪制時發現會發生視錐剔除(frustum-culling)的問題

查詢原因是沒生成Bounds的問題.（UE是通過邊緣檢測進行視錐剔除的）

可通過重寫UPrimitiveComponent::CalcBounds模擬一個Bounds

Ref:

unreal 的剔除原理:

https://docs.unrealengine.com/4.27/en-US/RenderingAndGraphics/VisibilityCulling/

 

e.g:

UCLASS()
class XXX_API
UCanvasGridProxy final : 
public
UPrimitiveComponent
{
    GENERATED_BODY()
public:
    UCanvasGridProxy()
    {
        PrimaryComponentTick.bCanEverTick = false;
    }
private:
    virtual FBoxSphereBounds CalcBounds(const FTransform& LocalToWorld) const override
    {
        FBoxSphereBounds b ;
        b.Origin = FVector(0);
        b.SphereRadius = 1000;
        b.BoxExtent.Set(1000, 1000, 1000);
        //b.SphereRadius = 1000;
        return  b;
    }
    virtual FPrimitiveSceneProxy* CreateSceneProxy() override
    {
        return new FCanvasGridProxy(this);
    }
};

如果要限制FPrimitiveSceneProxy的遮擋剔除可以重寫FPrimitiveSceneProxy::CanBeOccluded，自己計算遮擋剔除的運算邏輯

virtual bool CanBeOccluded() const override { return false; }//這里直接均不進行遮擋剔除

Note：CalcBounds的調用由UE完成，需要更新calcBounds函數時請調用函數:

UActorComponent::MarkRenderStateDirty()