| 摘要 |
Techniques are described herein for generating CAPTCHAs that include overlapped characters, projections on virtual three-dimensional (3D) surfaces, and/or virtual 3D objects. A CAPTCHA is a type of challenge-response test that a content provider may present to users for authorizing the users to access content that the content provider hosts. For example, when a user attempts to access content, a CAPTCHA may be generated in accordance with one or more of the techniques described herein and provided to the user. The user may be asked to identify characters that overlap in the CAPTCHA, characters that are projected on a virtual 3D surface, and/or a designated virtual 3D object, so that the user may be authorized to access the content. The user may enter the characters and/or select the designated virtual 3D object that is identified in the CAPTCHA using an input device, such as a keyboard, touch screen, pointing device, etc.
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