RTK is a framework for constructing raymarching shaders using TouchDesigner networks. It was originally derived from TDraymarchToolkit, but has since been rewritten.
The goal of RTK is to be able to use a network of connected OPs to construct a shader, using raymarching and signed distance functions.
In a sense, it's an attempt to create a new class of OP, whose output is a shader, rather than text, image, geometry, etc.
The term ROP or RTK OP refers to one of these operators.
Each ROP outputs a "definition" which can be used to construct a GLSL function along with all of its dependencies.
A definition is represented as a DAT table that has a header row and one or more definition rows, each corresponding to a single ROP. The first row after the header is always the definition outputting that table, and the rows below are upstream ROPs that feed into it (its dependencies).
Renderers are placed at the end of a chain, and are responsible for parsing the incoming definition and building a complete GLSL shader, and using that shader in a GLSL Multi TOP to render a video stream. Renderers are a special category because they are the only type of ROP that does not output its definition (though they do have an internal definition).
There are several types of functions that can be constructed using ROPs. They are distinguished by their return type and parameter types.
- SDF:
Sdf map(vec3 p, Context ctx) - 2D SDF:
Sdf map(vec2 p, Context ctx) - Value field:
float map(vec3 p, Context ctx) - Vector field:
vec4 map(vec3 p, Context ctx)
These take in a vec3 position, and return a Sdf struct, which contains the distance value, along with other values such as material assignments and settings.
These are like regular three dimensional SDFs but they take in two dimensional positions.
There are 3D SDF operators that take in a 2D one and use it to produce a 3D one, such as extrude and revolve.
These functions take in a vec3 position and return a single float value. For example, the fieldPointDistance operator returns the distance between the position and some other point.
Certain SDF operators can take secondary inputs with vector field functions. For example, the round operator can take a second input that it uses to determine how much rounding to apply for a given point in space.
These are like value field functions, but instead of returning a single float, they return a vec4.