从也是渲染目标的纹理采样 [英] Sampling from a texture which is also a render target

问题描述

我知道这在技术上不受支持(据我所知，这是未定义的行为)，但是从也要写入的纹理中采样确实是一件非常可怕的事情吗?

I know this technically isn't supported (and as far as I can tell it's undefined behavior) but is it really a fatally horrible thing to sample from a texture which is also being written to?

我问是因为我需要读取我也需要写的深度纹理，如果不能这样做，这意味着我将不得不复制深度纹理，如果这没什么大不了的我看不到仅仅复制它的危害吗?

I ask because I need to read from a depth texture which I also need to write to, if I can't do this it means I will have to copy the depth texture and if it isn't that big of a deal I don't see the harm in simply copying it?

感谢您的帮助！

推荐答案

是的，它是致命的，会触发未定义的行为.只需进行复制并从副本中读取即可.

Yes, it's fatal and triggers undefined behaviour. Just make a copy and read from the copy.

解释很简单.由于片段以未指定的顺序并行处理，因此您可能正在读取已写入的纹理像素或原始值纹理像素，并且无法知道正在读取的内容.进行复制并从中读取可以确保您读取正确的值.

The explanation is simple. Since fragments are processed in parallel in a unspecified order, you might be reading from already written texels or original value texels, and there is no way of knowing what you are reading. Making a copy and reading from it ensures that you will read the correct values.

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