Hello, I have a problem in rendering transparent materials such as glasses.
This is an example of the rendered image. You can see some part is correctly rendered, but other part becomes grey.
I think the reason may be simple, please let me know how to solve this problem. thanks

Thanks for the file, it explains the situation. The grey part in the image you posted is just the ground "box" under the structure being reflected in the glass (it is a strange sort of glass). You can more clearly observe this by removing the box, or by putting a large ground plane under it, or by putting a black & white checker material on it, and so forth.

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