# VTK (Visualization Toolkit)

## Overview

The Visualization Toolkit (VTK) is open source software for manipulating and displaying scientific data. It comes with state-of-the-art tools for 3D rendering, a suite of widgets for 3D interaction, and extensive 2D plotting capability. VTK is used by academicians for teaching and research; by government research institutions such as Los Alamos National Lab in the US or CINECA in Italy; and by many commercial firms who use VTK to build or extend products.

VTK is written in C++ and supports several different higher level language wrappers, including Python, Java and JavaScript. It is also the core engine for other tools like [Paraview](https://lfdocs.lookingglassfactory.com/software/third-party-apps-and-tools/paraview) and [Slicer 3D](https://lfdocs.lookingglassfactory.com/software/third-party-apps-and-tools/3d-slicer).

To learn more about VTK, visit [vtk.org](https://vtk.org/).

Looking Glass support has been added to the master branch of the [VTK source code](https://gitlab.kitware.com/vtk/vtk) as of Oct 1, 2020. To use VTK with Looking Glass support, you must build VTK from source.

## Prerequisites

If this is the first time setting up a Looking Glass, visit the [Getting Started page](http://learn.lookingglassfactory.com/onboarding) to make sure your display is set up correctly and ready to go.

This integration requires the following:

1. [HoloPlay Service](https://lookingglassfactory.com/software/holoplay-service) v1.1.3 or later. Use this [diagnostic tool](https://lfdocs.lookingglassfactory.com/looking-glass-bridge#test-your-setup) to check which version you have installed if unsure.
2. [HoloPlay Core SDK](https://lfdocs.lookingglassfactory.com/legacy/legacy-software/core-sdk)

## Getting Started

To use VTK with the Looking Glass, you have to enable the `VTK_MODULE_ENABLE_VTK_RenderingLookingGlass` flag in CMake when building.

In CMake:

1. Set `VTK_MODULE_ENABLE_VTK_RenderingLookingGlass` to ON
2. Edit `HoloPlayCore_INCLUDE_DIR` to point to header files directory `<your_path>/HoloPlayCoreSDK/HoloPlayCore/include`
3. Edit `HoloPlayCore_LIBRARY` to point to the dylib file of your corresponding platform library `<your_path>/HoloPlayCoreSDK/HoloPlayCore/dylib/<platform_specific>`
4. (Optional) If you would like to run the examples provided, turn on `BUILD_TESTING` too.

Build.

For more detailed instructions on how to build VTK, visit the [official VTK Wiki page](https://vtk.org/Wiki/VTK/Configure_and_Build).

## Usage

There are two different approaches to rendering in the Looking Glass. You can create an OS-specific Looking Glass render window and use it as you would a regular `vtkRenderWindow` (see `Testing/Cxx/TestDragon.cxx`). Alternatively, you can use the vtkLookingGlassPass as you would normally use a render pass in a renderer (see `Testing\Cxx\TestLookingGlassPass.cxx`).

If you have enabled `BUILD_TESTING` then you can run the following:

```bash
~/vtk-build $ cd bin
~/vtk-build/bin $ ./vtkLookingGlassCxxTests "TestDragon" -D ../ExternalData/Testing -I
```

This should create a window inside the Looking Glass display with graphics that produce a holographic image. (Note: you may need to drag terminal window inside Looking Glass before running the command)

## Troubleshooting

Make sure HoloPlay Service is running and can detect your device. See [this page](https://lfdocs.lookingglassfactory.com/looking-glass-bridge#test-your-setup) for more help.

## Support

For further VTK support, visit the [VTK Forum](https://discourse.vtk.org/).