I'm trying to implement a space carving algorithm to reconstruct 3D shape of a moving person. I have all the camera calibration data and projection matrices. Also I could get 2D image points from the 3D world coordinate system using the following steps:

```
i = 1;
x = P * [ X Y Z 1 ]';
u(i) = x(1)/x(3);
v(i) = x(2)/x(3);
```

where P is the projection matrix, [ X Y Z 1 ] is the 3D world coordinate system.

u & v represents the mapped 2D image points. I'm getting example values u=8.51e+02 and v=8.33e+02.

The question is how I can check what is the pixel intensity value corresponds to point (u,v)?