Node graphs are a standard way for artists to author custom materials. However, it is difficult to manually build and maintain node graphs that implement complex math expressions.

These expressions are more easily written in custom shader code, but not all rendering systems support custom code (e.g. Blender EEVEE).

Furthermore, shader code written in one language which can not always be compiled to all platforms. Node graphs can be translated to shaders for multiple plaftorms (e.g. Maya → viewport + Arnold, Blender → EEVEE + Cycles, UE4 → PC, console, and mobile).

To allow me to write shader code that can run in Blender EEVEE, I am writing and automatic system to build a node graph from shader code. Below is a simple expression in GLSL code, and its corresponding node graph output from my system is shown underneath.

I use glslang to compile the GLSL into an AST description. I then parse this AST output into an intermediate AST structure in memory, before converting this AST into a node graph represented as a set of nodes and connections between them. Finally, I reconstruct this node graph in the DCC (currently Blender) using its node scripting API.

// GLSL expression
vec3(
	r*cos(theta),
	r*sin(theta),
	LightSpaceGain
)

// glslang AST output
0:102        Construct vec3 ( temp 3-component vector of float)
0:99          component-wise multiply ( temp float)
0:99            'r' ( temp float)
0:99            cosine ( global float)
0:99              'theta' ( temp float)
0:100          component-wise multiply ( temp float)
0:100            'r' ( temp float)
0:100            sine ( global float)
0:100              'theta' ( temp float)
0:101          'LightSpaceGain' ( temp float)