iOS OpenGL ES 逻辑缓冲区加载
通过分析工具给出的 OpenGL API 使用性能警告列表，我发现我们每帧生成几个逻辑缓冲区负载 - 在这些地方我们没有清除缓冲区，因为绘制调用完全覆盖了它。
与直觉相反，在这些情况下引入 glClear() 调用只是将警告的位置移动到 glClear() 调用。 Apple 实现了 GL_EXT_discard_framebuffer，但是单独使用它也不足以阻止警告。 glDiscardFramebufferEXT() 后跟 glClear() 确实会停止警告，并显着提高性能，但 glClear() 调用本身需要时间清除缓冲区，在我们的用例中这是一个冗余操作。
其他人是否也发现他们需要调用这两个函数以避免重新加载成本，或者我是否遗漏了一些东西？是否有一种廉价的方式向 OpenGL 暗示帧缓冲区的内容即将被完全覆盖，因此不需要重新加载到图块内存中？
Slogging through the list of OpenGL API usage performance warnings given by the Analyze instrument, I am finding that we are generating several logical buffer loads per frame - places where we are not clearing a buffer because a draw call completely overwrites it.
Counterintuitively, introducing glClear() calls for these cases simply moves the location of the warning to the glClear() calls. Apple implement GL_EXT_discard_framebuffer, however using this on its own is also not sufficient to stop the warning. A glDiscardFramebufferEXT() followed by a glClear() does stop the warning, and improves performance significantly, but the glClear() call itself takes time to clear the buffer, which in our use case is a redundant operation.
Do others also find they need to call both functions to avoid the reload cost or am I missing something? Is there a cheap way of hinting to OpenGL that the contents of the framebuffer is about to be completely overwritten and so does not need to be reloaded into tile memory?
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该文档暗示全屏 glClear() 设置了一些神奇的标志，这与我在调试同一问题时所看到的一致。我不担心做多余的 glClear()，因为据我所知，这是预期的使用模式。
更新：您可能也遇到了与我相同的错误，我正在清除颜色和深度缓冲区，但在调用 glClear() 之前忘记设置 glDepthMask(GL_TRUE)。这导致了逻辑缓冲区负载警告。
The documentation implies that a fullscreen glClear() sets some magical flag, which is consistent with what I've seen while debugging the same issue. I wouldn't worry about doing a redundant glClear(), as this is the intended usage pattern from what I can tell.
Update: You may also be experiencing the same bug I had, where I was clearing the colour and depth buffers, but forgot to set glDepthMask(GL_TRUE) before calling glClear(). This resulted in a Logical Buffer Load warning.