shaders.cpp

#include <iostream>
#include <fstream>
#include <cstring>
// OSX systems need their own headers
#ifdef __APPLE__
#include <OpenGL/gl3.h>
#include <OpenGL/glext.h>
#include <GLUT/glut.h>
#else
#include <GL/glew.h>
#include <GL/glut.h>
#endif

using namespace std ; 

// This is a basic program to initiate a shader
// The textFileRead function reads in a filename into a string
// programerrors and shadererrors output compilation errors
// initshaders initiates a vertex or fragment shader
// initprogram initiates a program with vertex and fragment shaders

string textFileRead (const char * filename) {
	string str, ret = "" ; 
	ifstream in ; 
	in.open(filename) ; 
	if (in.is_open()) {
		getline (in, str) ; 
		while (in) {
			ret += str + "\n" ; 
			getline (in, str) ; 
		}
		//    cout << "Shader below\n" << ret << "\n" ; 
		return ret ; 
	}
	else {
		cerr << "Unable to Open File " << filename << "\n" ; 
		throw 2 ; 
	}
}

void programerrors (const GLint program) {
	GLint length ; 
	GLchar * log ; 
	glGetProgramiv(program, GL_INFO_LOG_LENGTH, &length) ; 
	log = new GLchar[length+1] ;
	glGetProgramInfoLog(program, length, &length, log) ; 
	cout << "Compile Error, Log Below\n" << log << "\n" ; 
	delete [] log ; 
}
void shadererrors (const GLint shader) {
	GLint length ; 
	GLchar * log ; 
	glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &length) ; 
	log = new GLchar[length+1] ;
	glGetShaderInfoLog(shader, length, &length, log) ; 
	cout << "Compile Error, Log Below\n" << log << "\n" ; 
	delete [] log ; 
}

GLuint initshaders (GLenum type, const char *filename) 
{
	// Using GLSL shaders, OpenGL book, page 679 

	GLuint shader = glCreateShader(type) ; 
	GLint compiled ; 
	string str = textFileRead (filename) ; 
	const GLchar * cstr = str.c_str() ; 
	glShaderSource (shader, 1, &cstr, NULL) ; 
	glCompileShader (shader) ; 
	glGetShaderiv (shader, GL_COMPILE_STATUS, &compiled) ; 
	if (!compiled) { 
		shadererrors (shader) ; 
		throw 3 ; 
	}
	return shader ; 
}

GLuint initprogram (GLuint vertexshader, GLuint fragmentshader) 
{
	GLuint program = glCreateProgram() ; 
	GLint linked ; 
	glAttachShader(program, vertexshader) ; 
	glAttachShader(program, fragmentshader) ; 
	glLinkProgram(program) ; 
	glGetProgramiv(program, GL_LINK_STATUS, &linked) ; 
	if (linked) glUseProgram(program) ; 
	else { 
		programerrors(program) ; 
		throw 4 ; 
	}
	return program ; 
}