OpenGL shaders compile but no rendering appears in the window - c++

Question

Both the vertex and fragment shader seem to be compiling and the window appears and is given the clear color but I cannot get the triangle to render. I have tried to just use the glBegin(); vertex(); glEnd(); as an alternative but this also resulted in no rendered triangle.
main.c
#include <stdio.h>
#include <unistd.h>
#include <gfx/shader.h>
#include <gfx/vbo.h>
#include <gfx/vao.h>
GLfloat vertices[] = {
0.0f,1.0f,0.0f,
1.0f,1.0f,0.0f,
-1.0f,-1.0f,0.0f
};
int main(void){
if(!glfwInit()){
fprintf(stderr, "Unable to init GLFW.\n");
exit(1);
}
GLFWwindow *win;
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
win = glfwCreateWindow(SCREENWIDTH, SCREENHEIGHT, "Terraria", NULL, NULL);
if(win==NULL){
fprintf(stderr, "Error creating opengl window\n");
glfwTerminate();
exit(1);
}
glfwMakeContextCurrent(win);
if(!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)){
fprintf(stderr, "Unable to init glad\n");
glfwTerminate();
exit(1);
}
glViewport(0, 0, 800, 600);
glfwSetFramebufferSizeCallback(win, frame_buffer_size_cb);
struct Shader s = create_shader("resources/shaders/vec2.vs", "resources/shaders/vec2.fs");
uint32_t vaoID, vboID;
glGenVertexArrays(1, &vaoID);
glBindVertexArray(vaoID);
glGenBuffers(1, &vboID);
glBindBuffer(GL_ARRAY_BUFFER, vboID);
glBufferData(vboID, 9*sizeof(GLfloat), vertices, GL_STATIC_DRAW);
while(!glfwWindowShouldClose(win)){
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(s.sh);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, vboID);
glVertexAttribPointer(
0,
3,
GL_FLOAT,
GL_FALSE,
3*sizeof(GLfloat),
(void*)0
);
glDrawArrays(GL_TRIANGLES, 0,3);
glDisableVertexAttribArray(0);
glfwSwapBuffers(win);
glfwPollEvents();
}
glfwTerminate();
return 0;
}
shader.h
#include <gfx/gfx.h>
struct Shader{
uint32_t sh;
uint32_t vsh;
uint32_t fsh;
};
struct Shader create_shader(const char *vs_path, const char *fs_path);
shader.c
#include <gfx/shader.h>
#include <string.h>
#include <stdio.h>
#include <assert.h>
static uint32_t _compile(int8_t id, const char *path, uint16_t type){
uint32_t sh; //Shader handle or ID
FILE *fp = fopen(path, "rb"); //Open the shader source code file
long sz = file_size(fp); //Get the file size
char *shaderSource; //Create object to holder shader source code
shaderSource = calloc(sz+1, 1);
fread(shaderSource, 1, sz, fp); //Read the shader source code into new buffer
fclose(fp);
assert(strlen(shaderSource)>0);
sh = glCreateShader(type);
glShaderSource(sh, 1, (const GLchar **)&shaderSource, NULL);
glCompileShader(sh);
int success;
char infoLog[512];
glGetShaderiv(sh, GL_COMPILE_STATUS, &success);
if (!success)
{
glGetShaderInfoLog(sh, 512, NULL, infoLog);
printf("Unable to compile shader id %d\n", id);
}
free(shaderSource);
return sh;
}
struct Shader create_shader(const char *vs_path, const char *fs_path){
struct Shader h;
h.vsh = _compile(1,vs_path, GL_VERTEX_SHADER);
h.fsh = _compile(0,fs_path, GL_FRAGMENT_SHADER);
h.sh = glCreateProgram();
glAttachShader(h.sh, h.vsh);
glAttachShader(h.sh, h.fsh);
glLinkProgram(h.sh);
// check for linking errors
int success;
char infoLog[512];
glGetProgramiv(h.sh, GL_LINK_STATUS, &success);
if (!success) {
glGetProgramInfoLog(h.sh, 512, NULL, infoLog);
printf("Unable to link gl program\n");
}
glDetachShader(h.sh, h.vsh);
glDetachShader(h.sh, h.fsh);
glDeleteShader(h.vsh);
glDeleteShader(h.fsh);
return h;
}
vertex shader
#version 330 core
layout (location = 0) in vec3 aPos;
void main(){
gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);
}
fragment shader
#version 330 core
out vec4 FragColor;
void main(){
FragColor = vec4(1.0,1.0,1.0,1.0);
}

Answer 1

I have found the answer. If you look really closely in main, it seems that you are actually supposed to call glBindBuffer to the macro GL_ARRAY_BUFFER and not to the vbo handle like I thought. Fixing this caused my program to function. Also my window hints were not taking effect because I was calling them after creating the window.