molecular-programgenerator

Generates complete shader programs from code snippets. You provide it with a set of input variables (e.g. vertex position, transform matrix and color), and one or more requested outputs (like vertex position and fragment color). It then attempts to create a tree out of the given code snippets that calculate the output variables from the input variables.

Snippet Files

Snippet files contain a series of functions, with each function having the following syntax.

digit = '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' ;
character = 'a' | 'b' ... 'z' | 'A' | 'B' ... 'Z' ;
number = [ '-' ], digit, { digit } ;
identifier = character, { character | digit } ;
parameter = [whitespace], identifier, whitespace, identifier, [whitespace] ;
attribute = 'fragment' | 'vertex' | 'low_q' | 'prio=', number ;
body = '{', ?text with balanced parantheses?, '}' ;
function = [whitespace], {attribute, whitespace}, identifier, whitespace, identifier, [whitespace], '(', [parameter, {',', parameter}], ')', [whitespace], body ;

Usage

Step 1: Load Snippet Files

Load text files with ProgramFile:

FILE* file = fopen("file1.txt", "r");
char buffer[4096]; // Assume files are not larger than 4K for simplicity
size_t size = fread(buffer, 1, 4096, file);

ProgramFile programFile1(buffer, buffer + size);
fclose(file);

Step 2: Feed File Contents Into Generator

ProgramGenerator generator;

for(auto& variable: programFile1.GetVariables())
    generator.AddVariable(variable);

for(auto& function: programFile1.GetFunctions())
    generator.AddFunction(function);

Alternatively, you can feed the program generator manually from C++, without using the snippet files:

ProgramGenerator::Function specular;
specular.stage = ProgramGenerator::Function::Stage::kFragmentStage;
specular.source =
        "if(dot(normal, -lightDirection0) > 0)\n"
        "\t{\n"
        "\t\tvec3 reflected = reflect(lightDirection0, normalize(normal));\n"
        "\t\tspecularLighting = pow(max(0.0, dot(reflected, eyeDirection)), shininess) * incomingLight0;\n"
        "\t}";
specular.inputs.push_back("lightDirection0"_H);
specular.inputs.push_back("normal"_H);
specular.inputs.push_back("eyeDirection"_H);
specular.inputs.push_back("shininess"_H);
specular.inputs.push_back("incomingLight0"_H);
specular.output = "specularLighting"_H;
generator.AddFunction(specular);

generator.AddVariable("lightDirection0", "vec3");
generator.AddVariable("normal", "vec3");
generator.AddVariable("eyeDirection", "vec3");
generator.AddVariable("shininess", "float");
generator.AddVariable("incomingLight0", "vec3");
generator.AddVariable("specularLighting", "vec3");

Step 3: Generate Programs

// Array containing both inputs and outputs:
std::array<Hash, 4> vars = {"positionAttribute"_H, "modelViewProjectionMatrix"_H, "gl_Position"_H, "fragmentColor"_H};
ProgramText program = generator.GenerateProgram(vars.begin(); vars.end());

myRenderer.CompileProgram(program.vertexShader, program.fragmentShader);