虚幻4 渲染一个BOX的过程

向场景增加MESH和更新MESH的位置等函数都在

\Engine\Source\Runtime\Renderer\Private\RendererScene.cpp

文件中。

渲染一个BOX首先在主线程通过调用这个函数向渲染线程发送命令，告诉渲染线程增加一个Primitive。

void FScene::AddPrimitive(UPrimitiveComponent* Primitive){SCOPE_CYCLE_COUNTER(STAT_AddScenePrimitiveGT);checkf(!Primitive->IsUnreachable(), TEXT("%s"), *Primitive->GetFullName());// Save the world transform for next time the primitive is added to the scenefloat DeltaTime = GetWorld()->GetTimeSeconds() - Primitive->LastSubmitTime;if ( DeltaTime < -0.0001f || Primitive->LastSubmitTime < 0.0001f ){

渲染线程会调用这个函数，添加信息到渲染线程可以读取的结构中。

void FScene::AddPrimitiveSceneInfo_RenderThread(FRHICommandListImmediate& RHICmdList, FPrimitiveSceneInfo* PrimitiveSceneInfo){SCOPE_CYCLE_COUNTER(STAT_AddScenePrimitiveRenderThreadTime);CheckPrimitiveArrays();int32 PrimitiveIndex = Primitives.Add(PrimitiveSceneInfo);PrimitiveSceneInfo->PackedIndex = PrimitiveIndex;PrimitiveBounds.AddUninitialized();PrimitiveVisibilityIds.AddUninitialize

最后在每一帧的render函数中，读取渲染线程可以读取的数据，遍历场景中可见物品，调用到这里，最后调用到D3D（windows下）的API

\Engine\Source\Runtime\Renderer\Private\DrawingPolicy.cpp

void FMeshDrawingPolicy::DrawMesh(FRHICommandList& RHICmdList, const FMeshBatch& Mesh, int32 BatchElementIndex, const bool bIsInstancedStereo) const{INC_DWORD_STAT(STAT_MeshDrawCalls);SCOPED_CONDITIONAL_DRAW_EVENTF(RHICmdList, MeshEvent, GEmitMeshDrawEvent != 0, TEXT("Mesh Draw"));const FMeshBatchElement& BatchElement = Mesh.Elements[BatchElementIndex];

如果一个mesh位置变化了，也会调用FScene里面的更新函数：

void FScene::UpdatePrimitiveTransform(UPrimitiveComponent* Primitive){SCOPE_CYCLE_COUNTER(STAT_UpdatePrimitiveTransformGT);// Save the world transform for next time the primitive is added to the scenefloat DeltaTime = GetWorld()->GetTimeSeconds() - Primitive->LastSubmitTime;if ( DeltaTime < -0.0001f || Primitive->LastSubmitTime < 0.0001f ){// Time was reset?Primitive->LastSubmitTime = GetWorld()-

和增加MESH一样，更新也会调用一个渲染线程的代码：

void FScene::UpdatePrimitiveTransform_RenderThread(FRHICommandListImmediate& RHICmdList, FPrimitiveSceneProxy* PrimitiveSceneProxy, const FBoxSphereBounds& WorldBounds, const FBoxSphereBounds& LocalBounds, const FMatrix& LocalToWorld, const FVector& OwnerPosition){SCOPE_CYCLE_COUNTER(STAT_UpdatePrimitiveTransformRenderThreadTime);const bool bUpdateStaticDrawLists = !PrimitiveSceneProxy->StaticElementsAlwaysUseProxyPrimitiveUniformBuffer();// Remove the primitive from the scene at its old location// (note that the octree update relies on the bounds not being modified yet).PrimitiveSceneProxy->GetPrimitiveSceneInfo()->RemoveFromScene(bUpdateStaticDrawLists);

虚幻4 主线程一直向渲染线程发送Task

http://blog.csdn.net/lqpgfz/article/details/51136345

渲染线程的Render也是通过主线程一直发送task来执行的。