bkornel/reproject-image-to-3d

Comparing a OpenCV's reprojectImageTo3D to my own

Reproject-Image-To-3D

Comparing a OpenCV's reprojectImageTo3D() to my own

// Reproject image to 3D
void customReproject(const cv::Mat& disparity, const cv::Mat& Q, cv::Mat& out3D)
{
	CV_Assert(disparity.type() == CV_32F && !disparity.empty());
	CV_Assert(Q.type() == CV_32F && Q.cols == 4 && Q.rows == 4);

	// 3-channel matrix for containing the reprojected 3D world coordinates
	out3D = cv::Mat::zeros(disparity.size(), CV_32FC3);

	// Getting the interesting parameters from Q, everything else is zero or one
	float Q03 = Q.at<float>(0, 3);
	float Q13 = Q.at<float>(1, 3);
	float Q23 = Q.at<float>(2, 3);
	float Q32 = Q.at<float>(3, 2);
	float Q33 = Q.at<float>(3, 3);

	// Transforming a single-channel disparity map to a 3-channel image representing a 3D surface
	for (int i = 0; i < disparity.rows; i++)
	{
		const float* disp_ptr = disparity.ptr<float>(i);
		cv::Vec3f* out3D_ptr = out3D.ptr<cv::Vec3f>(i);

		for (int j = 0; j < disparity.cols; j++)
		{
			const float pw = 1.0f / (disp_ptr[j] * Q32 + Q33);

			cv::Vec3f& point = out3D_ptr[j];
			point[0] = (static_cast<float>(j)+Q03) * pw;
			point[1] = (static_cast<float>(i)+Q13) * pw;
			point[2] = Q23 * pw;
		}
	}
}

Disparity map and Q matrix is from Martin Peris' Blog.