shaders.cpp

#include"shaders.h"

//text file to string
std::string get_file_contents(const char* filename)
{
	std::ifstream in(filename, std::ios::binary);
	if (in)
	{
		std::string contents;
		in.seekg(0, std::ios::end);
		contents.resize(in.tellg());
		in.seekg(0, std::ios::beg);
		in.read(&contents[0], contents.size());
		in.close();
		return(contents);
	}
	throw(errno);
}

//build the Shader Program from vertex and fragment shader
Shader::Shader(const char* vertexFile, const char* fragmentFile)
{
	// Read vertexFile and fragmentFile and store the strings
	std::string vertexCode = get_file_contents(vertexFile);
	std::string fragmentCode = get_file_contents(fragmentFile);

	// Convert the shader source strings into character arrays
	const char* vertexSource = vertexCode.c_str();
	const char* fragmentSource = fragmentCode.c_str();

	// Create Vertex Shader Object and get its reference
	GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
	// Attach Vertex Shader source to the Vertex Shader Object
	glShaderSource(vertexShader, 1, &vertexSource, NULL);
	// Compile the Vertex Shader into machine code
	glCompileShader(vertexShader);

	int success;
	char log[512];
	glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
	if (!success) {
		glGetShaderInfoLog(vertexShader, 512, 0, log);
		std::cerr << "[IN FILE]: " << vertexFile << std::endl;
		std::cerr << "ERROR::SHADER::VERTEX::COMPILATION_FAILED: " << log << std::endl;
	}

	// Create Fragment Shader Object and get its reference
	GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
	// Attach Fragment Shader source to the Fragment Shader Object
	glShaderSource(fragmentShader, 1, &fragmentSource, NULL);
	// Compile the Vertex Shader into machine code
	glCompileShader(fragmentShader);

	glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
	if (!success) {
		glGetShaderInfoLog(fragmentShader, 512, 0, log);
		std::cerr << "[IN FILE]: " << fragmentFile << std::endl;
		std::cerr << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED: " << log << std::endl;
	}

	// Create Shader Program Object and get its reference
	ID = glCreateProgram();
	// Attach the Vertex and Fragment Shaders to the Shader Program
	glAttachShader(ID, vertexShader);
	glAttachShader(ID, fragmentShader);
	// Wrap-up/Link all the shaders together into the Shader Program
	glLinkProgram(ID);

	glGetProgramiv(ID, GL_LINK_STATUS, &success);
	if (!success) {
		glGetProgramInfoLog(ID, 512, 0, log);
		fprintf(stderr, "ERROR::SHADER::PROGRAM::LINKING_FAILED: %s\n", log);
	}


	// Delete the now useless Vertex and Fragment Shader objects
	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);

}

// Activates the Shader Program
void Shader::Activate()
{
	glUseProgram(ID);
}

// Deletes the Shader Program
void Shader::Delete()
{
	glDeleteProgram(ID);
}