How to combine vector of 2D mat into a 3D mat ? Or

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How to combine vector of 2D mat into a 3D mat ? Or how can i directly fill up a 3d mat with 2d mats ?

This is my code but its not working

int planSize[] = { 48, 49, 49 };
cv::Mat voxel(3, planSize, CV_64FC1);
for (int i = 0; i < 48; i++)
    cv::filter2D(imageGray, voxel[i]), -1, texture[i]);