Don't get OpenGL output when using glVertexAttribFormat - opengl

Question

I'm trying to use glVertexAttribFormat and glVertexAttribBinding to create two triangles, but it doesn't work. I followed the description of how to do this in the question here (Render one VAO containing two VBOs). I don't really knnow what to try. I am new to OpenGL and all descriptions of glVertexAttribFormat appear to assume you already know OpenGL.
This is my code:
#include <glad/glad.h>
#include <glfw/glfw3.h>
#include <iostream>
void adjustViewportToWindowSize(GLFWwindow* window, int width, int height);
void checkEsc(GLFWwindow* window);
int main(void)
{
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
GLFWwindow* window = glfwCreateWindow(800, 600, "Tab name", NULL, NULL);
if (window == NULL)
{
std::cout << "Failed to create GLFW window" << std::endl;
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
{
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}
glViewport(0, 0, 800, 600); //size of GL rendering window.
glfwSetFramebufferSizeCallback(window, adjustViewportToWindowSize);
const char* vertexShaderSource = "#version 430 core\n"
"layout (location = 0) in vec3 aPos;\n"
"void main()\n"
"{\n"
" gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
"}\0";
const char* fragmentShaderSource = "#version 430 core\n"
"out vec4 FragColor;\n"
"void main()\n"
"{\n"
"FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
"}\0";
unsigned int vertexShader;
vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
glCompileShader(vertexShader);
unsigned int fragmentShader;
fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
glCompileShader(fragmentShader);
unsigned int shaderProgram;
shaderProgram = glCreateProgram();
//Attaching shaders to program
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
//Can delete shader objects after they are linked
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
float triangleVertices1[] = {
-0.50f, 0.0f, 0.0f,
-0.25f, 0.5f, 0.0f,
0.00f, 0.0f, 0.0f
};
float triangleVertices2[] = {
0.0f, 0.0f, 0.0f,
0.25f, 0.5f, 0.0f,
0.5f, 0.0f, 0.0f
};
unsigned int aVBO[2], VAO2;
glGenVertexArrays(1, &VAO2);
glBindVertexArray(VAO2);
glVertexAttribFormat(0, 3, GL_FLOAT, GL_FALSE, 0); //format setup without a buffer
glVertexAttribBinding(0, 0);
glBindVertexArray(0);
//Bind Buffers to data next
glGenBuffers(2, aVBO);
glBindBuffer(GL_ARRAY_BUFFER, aVBO[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(triangleVertices1), triangleVertices1, GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, aVBO[1]);
glBufferData(GL_ARRAY_BUFFER, sizeof(triangleVertices2), triangleVertices2, GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, 0);
while (!glfwWindowShouldClose(window))
{
checkEsc(window);
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(shaderProgram);
glBindVertexArray(VAO2);
glBindVertexBuffer(0, aVBO[0], 0, 3*sizeof(float));
glDrawArrays(GL_TRIANGLES, 0, 3);
glBindVertexBuffer(0, aVBO[1], 0, 3*sizeof(float));
glDrawArrays(GL_TRIANGLES, 0, 3);
glBindVertexArray(0);
glfwSwapBuffers(window);
glfwPollEvents();
}
//Clear up
glDeleteVertexArrays(1, &VAO2);
glDeleteBuffers(1, aVBO);
glDeleteProgram(shaderProgram);
glfwTerminate();
return 0;
}
void adjustViewportToWindowSize(GLFWwindow* window, int width, int height)
{
glViewport(0, 0, width, height);
}
void checkEsc(GLFWwindow *window)
{
if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
glfwSetWindowShouldClose(window, true);
}
Can also be accessed on github: https://github.com/Ritzerk/OpenGLSelfStudy

Answer 1

In addition to setting up the buffer bindings, you also have to enable the vertex attribute in the shader. To do so, you have to call glEnableVertexAttribArray during VAO setup:
glBindVertexArray(VAO2);
glVertexAttribFormat(0, 3, GL_FLOAT, GL_FALSE, 0);
glVertexAttribBinding(0, 0);
//Enable input in shader
glEnableVertexAttribArray(0);
glBindVertexArray(0);