Cannot get Triangle to Display with OpenGL in GLFW [closed] - c++

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I have been following the Modern Opengl Tutorials on YouTube by Nico Cvitak to help me transition from SDL to OpenGl/GLFW; here is a link to the lesson I can't get to work: [https://www.youtube.com/watch?v=2K_R4C1UP-c][1]
Here is my code:
myVertexShader.vs
#version 150 core
in vec2 v_pos;
void main()
{
gl_Position = vec4(v_pos, 0.0, 1.0);
}
myFragmentShader.fs
#version 150 core
out vec4 fragData;
void main()
{
fragData = vec4(1.0, 1.0, 1.0, 1.0);
}
main.cpp
#define GLFW_INCLUDE_GLCOREARB
#include <iostream>
#include <GLFW/glfw3.h>
#include <OpenGL/OpenGL.h>
#include "ShaderUtils.h"
int main(int argc, const char * argv[])
{
GLFWwindow * window;
//Initialize the library
if (!glfwInit())
return -1;
//Specify Hints
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
//Create a windowed mode window and its OpenGL context
window = glfwCreateWindow(640, 480, "Mojicon", NULL, NULL);
if (!window)
{
glfwTerminate();
return 1;
}
//Make the window's context current
glfwMakeContextCurrent(window);
std::cout << glGetString(GL_VERSION) << std::endl;
glClearColor(0.0, 0.0, 0.0, 1.0);
GLuint vertexShader = ShaderUtils::createShaderFromFile("myVertexShader.vs", GL_VERTEX_SHADER);
GLuint fragmentShader = ShaderUtils::createShaderFromFile("myFragmentShader.fs", GL_FRAGMENT_SHADER);
GLuint shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glBindFragDataLocation(shaderProgram, 0, "fragData");
glLinkProgram(shaderProgram);
GLint linkStatus;
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &linkStatus);
if (linkStatus != GL_TRUE)
{
cout << "Program Link Failed!" << endl;
GLint infoLogLength;
glGetProgramiv(shaderProgram, GL_INFO_LOG_LENGTH, &infoLogLength);
GLchar * infoLog = new GLchar[infoLogLength + 1];
glGetShaderInfoLog(shaderProgram, infoLogLength + 1, NULL, infoLog);
cout << infoLog << endl;
delete infoLog;
return 0;
}
glUseProgram(shaderProgram);
//vertex buffer objects
GLuint myVBO;
glGenBuffers(1, &myVBO);
glBindBuffer(GL_ARRAY_BUFFER, myVBO);
GLfloat bufferData[] =
{
+0.0, +0.5,
-0.5, -0.5,
+0.5, -0.5,
};
glBufferData(GL_ARRAY_BUFFER, sizeof(bufferData), bufferData, GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, NULL);
GLuint myVAO;
glGenVertexArrays(1, &myVAO);
glBindVertexArray(myVAO);
GLint positionLoc = glGetAttribLocation(shaderProgram, "v_pos");
glEnableVertexAttribArray(positionLoc);
glBindBuffer(GL_ARRAY_BUFFER, myVBO);
glVertexAttribPointer(positionLoc, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(GLfloat), 0);
glBindBuffer(GL_ARRAY_BUFFER, NULL);
glBindVertexArray(NULL);
//Loop the window until closed
while (!glfwWindowShouldClose(window))
{
//Render here
GLint windowWidth, windowHeight;
glfwGetWindowSize(window, &windowWidth, &windowHeight);
glViewport(0, 0, windowWidth, windowHeight);
glClear(GL_COLOR_BUFFER_BIT);
glBindVertexArray(myVAO);
glDrawArrays(GL_TRIANGLES, 0, 3);
glBindVertexArray(NULL);
//Poll for events
glfwPollEvents();
//Swap buffers
glfwSwapBuffers(window);
}
glDeleteBuffers(1, &myVBO);
glDeleteVertexArrays(1, &myVAO);
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
glDeleteProgram(shaderProgram);
glfwDestroyWindow(window);
glfwTerminate();
return 0;
}
ShaderUtil.h
#define GLFW_INCLUDE_GLCOREARB
#include <iostream>
#include <fstream>
#include <streambuf>
#include <GLFW/glfw3.h>
using namespace std;
class ShaderUtils
{
public:
static GLuint createShaderFromFile(const GLchar * path, GLenum shaderType);
};
ShaderUtil.cpp
#include "ShaderUtils.h"
GLuint ShaderUtils::createShaderFromFile(const GLchar * path, GLenum shaderType)
{
GLuint shaderID = glCreateShader(shaderType);
ifstream fin;
fin.open(path);
if (!fin.is_open())
{
cout << "File Not Found '" << path << "'!" << endl;
return -1;
}
string source((istreambuf_iterator<GLchar>(fin)), istreambuf_iterator<GLchar>());
fin.close();
const GLchar * shaderSource = source.c_str();
glShaderSource(shaderID, 1, &shaderSource, NULL);
glCompileShader(shaderID);
GLint compileStatus;
glGetShaderiv(shaderID, GL_COMPILE_STATUS, &compileStatus);
if (compileStatus != GL_TRUE)
{
cout << "Shader Failed To Compile: '" << path << "'!" << endl;
GLint infoLogLength;
glGetShaderiv(shaderID, GL_INFO_LOG_LENGTH, &infoLogLength);
GLchar * infoLog = new GLchar[infoLogLength + 1];
glGetShaderInfoLog(shaderID, infoLogLength + 1, NULL, infoLog);
cout << infoLog << endl;
delete infoLog;
return -1;
}
return 0;
}
I tried to make this code nearly identical with the tutorials code, and I cannot for the life of me find any differences. Help me find the problem (there are no bugs) and explain it to me.

Answer 1

Your createShaderFromFile() method always returns 0:
GLuint ShaderUtils::createShaderFromFile(const GLchar * path, GLenum shaderType)
{
...
return 0;
}
You use this return value as a shader id:
GLuint vertexShader = ShaderUtils::createShaderFromFile(
"myVertexShader.vs", GL_VERTEX_SHADER);
GLuint fragmentShader = ShaderUtils::createShaderFromFile(
"myFragmentShader.fs", GL_FRAGMENT_SHADER);
These values will come out as 0. To make this work, you will need to return the shader id from the method:
GLuint ShaderUtils::createShaderFromFile(const GLchar * path, GLenum shaderType)
{
...
return shaderID;
}
You should be able to track down this kind of problem by stepping through the code in a debugger.