3D rendering in OpenCV

Question

I am doing a project on 3D rendering of a scene. I am using OpenCV. The steps I am doing are like this:

1. Taking two images of a scene.
2. Calculating object

Answer 1

you can have Q matrix from stereo rectification via openCV method:

cv::stereoRectify

I think you want the Q matrix to reconstruct the 3D. However, you can reconstruct from intrinsic parameters via:

X = (u-cu)*base/d
Y = (v-cv)*base/d
Z = f*base/d 

where (u,v) is a 2D point in the image coordinate system, (cu,cv) is the principal point of the camera, f is the focal length, base is the baseline, d is the disparity and (X,Y,Z) is a 3D point in the camera coordinate system.