Getting black screen when using glCreateVertexArrays - c++

Question

I am learning opengl right now. I have bought a book called OpenGL Superbible. But I couldn't survived to properly configure the environment. I use GLFW 3.2 as windowing toolkit (if that is what it is called) and GLEW 2.0.
I am trying to compile and use shaders to draw on screen. According to the book this should draw a triangle on screen. But it doesn't. Instead, it shows the clear background color that is set by glClearColor.
This is the Code:
#include <iostream>
#include <GLFW\glfw3.h>
#include <GL\glew.h>
GLuint CompileShaders();
int main(void) {
// Initialise GLFW
if (!glfwInit()) {
fprintf(stderr, "Failed to initialize GLFW\n");
getchar();
return -1;
}
// Open a window and create its OpenGL context
GLFWwindow *window;
window = glfwCreateWindow(1024, 768, "Tutorial 01", NULL, NULL);
if (window == NULL) {
fprintf(stderr, "Failed to open GLFW window. If you have an Intel GPU, "
"they are not 3.3 compatible. Try the 2.1 version of the "
"tutorials.\n");
getchar();
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
// Initialize GLEW
if (glewInit() != GLEW_OK) {
fprintf(stderr, "Failed to initialize GLEW\n");
getchar();
glfwTerminate();
return -1;
}
// Ensure we can capture the escape key being pressed below
glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);
GLuint RederingProgram = CompileShaders();
GLuint VertexArrayObject;
glCreateVertexArrays(1, &VertexArrayObject);
glBindVertexArray(VertexArrayObject);
int LoopCounter = 0;
do {
// Clear the screen. It's not mentioned before Tutorial 02, but it can cause
// flickering, so it's there nonetheless.
/*const GLfloat red[] = {
(float)sin(LoopCounter++ / 100.0f)*0.5f + 0.5f,
(float)cos(LoopCounter++ / 100.0f)*0.5f + 0.5f,
0.0f, 1.0f
};*/
// glClearBufferfv(GL_COLOR, 0, red);
// Draw nothing, see you in tutorial 2 !
glUseProgram(RederingProgram);
glDrawArrays(GL_TRIANGLES, 0, 3);
// Swap buffers
glfwSwapBuffers(window);
glfwPollEvents();
} // Check if the ESC key was pressed or the window was closed
while (glfwGetKey(window, GLFW_KEY_ESCAPE) != GLFW_PRESS &&
glfwWindowShouldClose(window) == 0);
// Close OpenGL window and terminate GLFW
glfwTerminate();
return 0;
}
GLuint CompileShaders() {
GLuint VertexShader;
GLuint FragmentShader;
GLuint Program;
static const GLchar *VertexShaderSource[] = {
"#version 450 core "
" "
"\n",
" "
" \n",
"void main(void) "
" "
"\n",
"{ "
" "
" \n",
"const vec4 vertices[3] = vec4[3](vec4(0.25, -0.25, 0.5, 1.0),\n",
" "
"vec4(-0.25, -0.25, 0.5, 1.0),\n",
" "
"vec4(0.25, 0.25, 0.5, 1.0)); \n",
" gl_Position = vertices[gl_VertexID]; \n",
"} "
" "
" \n"};
static const GLchar *FragmentShaderSource[] = {
"#version 450 core "
" "
"\n",
" "
" \n",
"out vec4 color; \n",
" "
" \n",
"void main(void) "
" "
"\n",
"{ "
" "
" \n",
" color = vec4(0.0, 0.8, 1.0, 1.0); \n",
"} "
" "
" \n"};
// Create and compile vertex shader.
VertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(VertexShader, 1, VertexShaderSource, NULL);
glCompileShader(VertexShader);
// Create and compile fragment shader.
FragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(FragmentShader, 1, FragmentShaderSource, NULL);
glCompileShader(FragmentShader);
// Create program, attach shaders to it, and link it
Program = glCreateProgram();
glAttachShader(Program, VertexShader);
glAttachShader(Program, FragmentShader);
glLinkProgram(Program);
// Delete the shaders as the program has them now.
glDeleteShader(FragmentShader);
glDeleteShader(VertexShader);
return Program;
}
I am working in visual studio 2015. I have all the libraries to develop some opengl (I think), but somethig is wrong. Please help me. By the way, glCreateVertexArrays() function is only in Opengl 4.5 and above, I know, since the book is explained in opengl 4.5.
I will go crazy soon because no proper tutorials for beginners. People who have learned this are very ambitious people. I bow before those people.

Answer 1

Your shaders shouldn't compile:
glShaderSource(VertexShader, 1, VertexShaderSource, NULL);
This tells the GL that it should expect an array of 1 GLchar pointers. However, your GLSL code is actually split into several individual strings (note the commas);
static const GLchar *VertexShaderSource[] = {
"...GLSL-code..."
"...GLSL-code..."
"...GLSL-code...", // <- this comma ends the first string vertexShaderSource[0]
"...GLSL-code..." // vertexShaderSource[1] starts here
[...]
There are two possible solutions:
Just remove those commas, so that your array contains of just one element pointing to the whole GLSL source as one string.
Tell the GL the truth about your data:
glShaderSoure(..., sizeof(vertexShaderSource)/sizeof(vertexShaderSource[0]), vertexShaderSource, ,,,)
Apart from that, you should always query the compilation and link status of your shaders and program objects. Also query the shader compilation and program link info logs. They will contain human-readbale messages telling you why the compilation / link did fail.