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shaders.cpp
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shaders.cpp
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#include <iostream>
#include <fstream>
#include <GLUT/glut.h>
#include <cstring>
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);
GLchar * cstr = new GLchar[str.size()+1];
const GLchar * cstr2 = cstr; // Weirdness to get a const char
strcpy(cstr,str.c_str());
glShaderSource (shader, 1, &cstr2, 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;
}