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UDT - Camera frame clipping according to a region of the target

August 9, 2017 - 7:50am #1

Hi,

I have this project that propose realistic AR experience. To achieve this, one of the steps is get the pixel information of determinated region of the user defined target. So what I need to do is "back project" the coordinates of a region of the target to the camera frame and then get the information of the pixels.

How can I do this "back projection" from the "world coordinates" of the target to the camera frame coordinates?

 

P.S.

I'm already did the part of getting the camera frame and make a texture of it. And I tried to do this back projection by multiplying the model view projection matrix by the points position of my interest according to the target. But when I renderizes the texture of this points of interest I only see noises.

UDT - Camera frame clipping according to a region of the target

August 9, 2017 - 11:25am #3

Thanks for the reply, Strasza.

Have you confirmed that the camera frame you are capturing is displaying correctly before performing further operations?

Yes, I've confirmed. I created  a Quad Class based on the Teapot class and applied the texture on the Quad as you can see on this screenshot of the app.

http://imgur.com/QVQBiYk

Regard to the "back projection" mentioned by me, I found that post

https://developer.vuforia.com/forum/faq/technical-how-can-i-project-target-point-screen

and implemented the code in my app. That transformation seems to be working. But when viewing the values (through the logs in debug mode) of the center of the trackable (0, 0, 0) transformed in a screen point, I realized that when the point are in the limits of the screen (bottom right corner) they assume values outside of the frame resolution (in my case 1280x720). Could you tell me why this is happening and what is the expected resolution of the screen based on the frame resolution?

I believe the image noises I saw were caused by the wrong "back projection".

UDT - Camera frame clipping according to a region of the target

August 9, 2017 - 10:03am #2

Hello hemerson,

What do you mean when you say "I only see noises?" Have you confirmed that the camera frame you are capturing is displaying correctly before performing further operations?

Thanks,

-Vuforia Support

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