Log in or register to post comments

Gap between marker and augmented object

May 15, 2014 - 5:37am #1

Hi,

Just to give the context : 

I use Vuforia to get the pose, then I extract the camera's vectors (position, direction , up) to set them in my 3D rendering engine, after a 90° rotation along X (not the same reference frame). I made the choice to move the camera and not the 3D object, that's why I extract these parameters from the MV matrix.

So, now, when I compare the vuforia sample and my application I see that the result is not the same, I have not enought precision : 

When the marker is on the center of the screen, all is good.

On the side, the augmenter aubject is no longer at the center of the marker.

 

My first idea was the FOV, I get it folowing the documentation and set it on my 3D persperctive camera, without fixing the issue.

So the question is : What other parameters I missed ?

 

Thanks !

Gap between marker and augmented object

May 22, 2014 - 9:11am #7

Ah, I see; basically a FOV aspect ratio issue.

Glad that it works now.

Gap between marker and augmented object

May 22, 2014 - 8:48am #6

Found it I think : 

The FOV computed from the AR settings is not to be used direclty in the 3D perspective camera due to the different size between the capture size and the rendering size.

Now the object follow the marker with a quite good precision :-)

Gap between marker and augmented object

May 19, 2014 - 4:25am #5

Not yet, but it my last chance.

From the MVmatrix, I get the camera's vector to set them in my engine (position, direction, up) and nothing else; My 3D model starts from the center of the scene, I didn't saw any other parameters to consider.

 

Thanks !

Gap between marker and augmented object

May 19, 2014 - 4:15am #4

In that case, the only other thing I can think of is that there is probably some difference between the modelview matrix in the samples and the one that you build using your own 3D engine;

have you tried logging the values of your engine model-view matrix and compare with the ones produced by the sample code ?

 

 

Gap between marker and augmented object

May 19, 2014 - 4:07am #3

Hi !

I compared my render of the video background with Vuforia's sample and its the same, so my viewport seems good. 

I'll check the FOV again, but i'm pretty sure it is good too...

If you have any more idea...

 

Thanks !

Gap between marker and augmented object

May 18, 2014 - 11:40am #2

Hi Ange3d,

I think we already exchanged a couple of posts on Background texture Access and OpenGL on similar issue :-))

anyway, there are just 2 things that come to my mind as possibly / potentilly affecting your engine in this case:

- FOV (but as you say, you aready set this, so I assume this is correct)

- GL viewport; Vuforia renders a portion of the camera view outside the boundaries of your screen; this is done oin order to obtain a "screen fit" due to the different aspect ratio of the screen vs. the camera image.

Check the Background Texture Access sample, in particular the configureVideoBckground() function and the viewport settings...

 

Log in or register to post comments