Unreal笔记禁止Actor或Component进行视锥剔除(frustumculling)(Render)

自定义UPrimitiveComponent时，通过PDI进行绘制时发现会发生视锥剔除(frustum-culling)的问题

查询原因是没生成Bounds的问题.（UE是通过边缘检测进行视锥剔除的）

可通过重写UPrimitiveComponent::CalcBounds模拟一个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的遮挡剔除可以重写FPrimitiveSceneProxy::CanBeOccluded，自己计算遮挡剔除的运算逻辑

virtual bool CanBeOccluded() const override { return false; }//这里直接均不进行遮挡剔除

Note：CalcBounds的调用由UE完成，需要更新calcBounds函数时请调用函数:

UActorComponent::MarkRenderStateDirty()