Even though the HTC EVO 3D has not been given the full root treatment yet, there is still a way to take screenshots on the unrooted device, thanks to No Root Screenshot It. As a matter of fact, the picture you see to the right was taken on a 100% stock, completely unrooted EVO 3D.
The app is available in the Market and will set you back $4.99, but it might be worth the investment if you need to take screenshots on your EVO 3D or simply don't want to root your HTC EVO 4G. (The HTC EVO View 4G actually has built-in screenshot capabilities, so no root access or special apps are required for it.)
Setting up No Root Screenshot It is quite quick and easy, but it does require access to a Windows PC or Mac. During the set-up process, you will be prompted to download additional software to your computer, which you will run while your phone is connected with the USB cable. However, once this set-up is complete, you can take screenshots with only the phone; it is not necessary to keep it plugged in to your computer. You can see what the Windows software looks like below.
No Root Screenshot It claims that it works with every Android phone, but we can only confirm compatibility with the EVO 4G and EVO 3D (which is all you should really care about, anyway). Just keep in mind that you will need to run the set-up again if you restart your phone – unfortunately it doesn't stick between reboots.
Give it a try, and see how you like it. It might not be the best solution, but it's the best we've got until we can fully experience the bliss of a rooted EVO 3D (unless we want to mess with the SDK).