Note: Force push to force a re-run of build tests. The previous tests
failed in an unrelated module. I assume it's a bug that occured
randomly.

warper.

Useful for debug purposes:
    cmake -DDEBUG_POST="ocv_cmake_dump_vars(CUDA)" .
    cmake -DCMAKE_PRE="ocv_cmake_dump_vars(\"OPENCL|opencl\")" .

related: #5845

When I reconstructed the 3D scene I want to show it as viz::WMesh with an initial value of lighting. For this I disable lighting and shadows:
cv::viz::Viz3d viz_3d_window("3D");
viz_3d_window.setRenderingProperty("mesh", cv::viz::LIGHTING, 0);

Most of the examples show the 3D reconstruction using the point cloud, but using  the mesh one part of it creates a shadow on other parts of it if lighting ON.
Using a 3D mesh with disabled lighting gives the most realistic picture of the reconstructed 3D scene.

by using the indices from the sorted distance vector of pairs.

In case of binary class, pred_m is initialized as zero vector and later
returned when raw outputs are requested, but it is never filled.