add windows build doc

Author: weigao95

doc/ubuntu_pcl_build.md

@@ -1,6 +1,6 @@
 ### Building SurfelWarp on Ubuntu 16.04 with `PCL 1.8`
 
-You need a nvidia GPU with `CUDA 9`  installed. Note that `CUDA 10` is not compatible with `PCL 1.8` and doesn' work. If you want to build with `CUDA 10`, please follow this document.
+You need a nvidia GPU with `CUDA 9`  installed. Note that `CUDA 10` is not compatible with `PCL 1.8` and doesn' work. If you want to build with `CUDA 10`, please follow [this document](https://github.com/weigao95/surfelwarp/blob/master/doc/ubuntu_cliantro_build.md).
 
 To choose the CUDA architecture [compatible](https://en.wikipedia.org/wiki/CUDA#GPUs_supported) with your `CUDA` version and graphics card, thereby also reducing compile time, pass `-DCUDA_ARCH=<arg>` to CMake, where `<arg>` is a two-digit compile compatibility version, e.g. "61", or choose this number from the corresponding drop-down in `cmake-gui`.
 

doc/windows_pcl_build.md

@@ -0,0 +1,11 @@
+### Building SurfelWarp on Windows with `PCL 1.8`
+
+Building with `PCL` has been tested on Visual Studio 2015 with `CUDA 9.2`  and `cmake 3.9.6`. Note that `CUDA 10` and higher versions are not compatible with `PCL` and won't work.  `CUDA` and `cmake` can be installed from their official websites. The community version of Visual Studio is sufficient. `OpenCV` can be downloaded from the official website as a prebuilt-binaries-and-header package and extracted to a location of your choosing. 
+
+**This code and all its dependencies MUST be built in 64 bit**. In other words, you should select the **Win64** (or, for later CMake versions, **x64**) generator in `cmake`.
+
+The build-and-installation procedures for `PCL`, and `GLFW` are very similar. All of these packages are managed by `CMake` and you can follow the standard procedure to generate the Visual Studio solution. After solution generation, open it in Visual Studio running as an administrator (right-click the VS icon and choose `Run as administrator`). You can then build and install the package using the `INSALL` project inside the solution. The standard configuration of these packages should be sufficient, although some debug code might require the GPU support of `PCL`.
+
+Now you are ready to build this repo. To tell CMake where to find the dependencies, you can set `PCL_DIR` to the location of _PCLConfig.cmake_ on disk, and likewise for `glfw3_DIR`, `OpenCV_DIR`, and/or any other dependencies. Alternatively, add these as permanent [environment variables](https://www.architectryan.com/2018/08/31/how-to-change-environment-variables-on-windows-10/) to simplify future builds.  After that, just follow the standard `CMake` and Visual Studio workflow to build this repo. 
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