![]() The occlusion process happens in this thread and it happens per object. ![]() This is mostly done on the CPU, but there are some parts on the GPU as well. ![]() This includes animations, physics, AI, and all the logic that happens in our application.ĭraw thread (CPU): it calculates what to include in the rendering. Game thread (CPU): it calculates all the transformations of the objects in the scene. The render of a frame starts in the main game thread: You can see the time every thread spends for a frame by typing stat unit in the console: To know more about this, check the Unreal documentation: Parallel Rendering.Īs briefly described above, Unreal uses three main threads to renders a frame. To make sure your code is called by the right thread, you can add checks such as check(IsInGameThread()) or check(IsInRenderingThread()) for improving code stability.įinally, a new thread, the RHI Thread, executes these commands via the appropriate graphics API on the backend. The game thread inserts the command into the rendering command queue, and the rendering thread calls the execute function when it gets around to it. It works creating a class with a virtual Execute function that contains the code you enter into the macro. The primary method of communication between the two is the ENQUEUE_RENDER_COMMAND macro: it serves to enqueue platform-agnostic render commands into the renderer’s command list. It operates in parallel with the Game Thread and it’s usually one or two frames behind it. The renderer code runs in a separate thread, the Rendering Thread. Here is the complete UE4 documentation for graphics programming: UE4 Graphics Programming. You have to take care of every memory read and write not only to ensure thread safety, but also to avoids race conditions. Rendering in Unreal it’s a complex area, especially if you want to make modifications to customize it for your purposes. Here is where the magic happens to allow the abstract rendering code to work on different platforms using different APIs. The RHI (Render Hardware Interface) is the other key module for graphics programming as it is the interface for rendering APIs. ![]() However, when the Engine needs to call some code in the Renderer, this happens through the IRendererModule interface. The Renderer module depends on the Engine module because it has many callbacks into it. The code for rendering exists in the Renderer module, which is compiled to a shared library (e.g.dll on Windows) to allow faster iteration. In this article, I would like to write down a brief description of the rendering process in Unreal Engine 4 and analyze how the engine approaches the main elements of real time rendering. Unreal Engine 4 has a really complex multi-platform and multi-threaded rendering engine. ![]()
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