RayTK is a library of TouchDesigner components that construct raymarching shaders (and other types of shaders) with networks of COMPs using the TouchDesigner network editor.
The goal of RayTK is to allow artists without a strong knowledge of GLSL to render raymarched scenes, using the familiar elements of the TouchDesigner network editor. Raymarching has been around for a long time, but it is very different from traditional rendering, and it normally requires a strong knowledge of GLSL and vector math.
RayTK supports things like reflections, soft shadows, and effectively infinite geometry detail.
The toolkit itself can be downloaded from GitHub.
There are also lots of tutorials on YouTube.
The toolkit website has more information including reference documentation.