Hi all. Recently I had started learning opengl. I decided that it would be easier for me in the long run if I could wrap some code I had written of the opengl function calls within classes. At the moment I have been trying to get a texture to show up on a rectangle. However the code runs with either a completely black or no rectangle at all. I had messed around with the code and found out it may be related to calling glVertexAttribPointer(…) and glEnableVertexAttribArray(…). If i leave these outside the function the code works fine, however I would really like to put these into a method. Relative code is posted below (If you need me to provide additional files please let me know).
I would also like to add that if you have any tips for me, please feel free to say so. Thanks.
Problematic code located halfway in window.cpp
Window.cpp
#include "Window.h"
#include "Error.h"
#include "VertexArray.h"
#include "Buffer.h"
#include "Program.h"
#include "Texture.h"
#include <GL\glew.h>
#include <iostream>
Window::Window(unsigned int windowWidth, unsigned int windowHeight) : _windowWidth(windowWidth), _windowHeight(windowHeight){ ... }
Window::~Window() { ... }
void Window::run(void)
{
SDL_Event e;
SDL_Event e;
_running = true;
/*----------------------*/
VertexArray VAO;
const float vertices[] =
{
// Positions //Colors //Texture Coordinates
0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, // top right
0.5f, -0.5f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, // bottom right
-0.5f, -0.5f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, // bottom left
-0.5f, 0.5f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f //top left
};
const unsigned int indicies[] =
{
0, 1, 3, //First Triangle (Vert 0, Vert 1, Vert 3)
1, 2, 3
};
//Generate Texture
Texture texture(GL_TEXTURE_2D);
texture.bind();
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
texture.unbind();
texture.loadImage("wall.jpg");
Buffer EBO(GL_ELEMENT_ARRAY_BUFFER);
EBO.loadData(indicies, 6, GL_STATIC_DRAW);
VAO.bindBuffer(EBO);
Buffer VBO(GL_ARRAY_BUFFER);
VBO.loadData(vertices, 32, GL_STATIC_DRAW);
Program PGRM("VertexShader.vert", "FragmentShader.frag");
{
//HERE BE ERRORS???
//VAO.bindAttribute(VBO, 0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
//VAO.bindAttribute(VBO, 1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
//VAO.bindAttribute(VBO, 2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
/* CODE HERE WORKS FINE*/
VAO.bind();
VBO.bind();
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glVertexAttribPointer(
1, //Attribute location 1
3, //Color values have size3
GL_FLOAT, //color values are of float value
GL_FALSE, //Do not normalize (translte into normalized screen coor)
8 * sizeof(float), //Stride value
(void*)(3 * sizeof(float)) //3 floats to the right is the offset to our color data
);
glEnableVertexAttribArray(1);
glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
glEnableVertexAttribArray(2); //Remember now its 8 elements per vertex
//Remember to unbind vbo and attr pointer when done with vao
VBO.unbind();
VAO.unbind();
EBO.unbind();
}
while (_running)
{
handleEvent(e);
glClear(GL_COLOR_BUFFER_BIT);
texture.bind();
PGRM.useProgram();
VAO.bind();
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
glBindVertexArray(0);
PGRM.unuseProgram();
SDL_GL_SwapWindow(_window);
}
}
void Window::handleEvent(SDL_Event &e) { ... }
VertexArray.h
#pragma once
#include "Buffer.h"
#include "GLobject.h"
#include <iostream>
#include <GL\glew.h>
class VertexArray : public GLobject
{
public:
VertexArray() : GLobject()
{
glGenVertexArrays(1, &_objectId);
}
~VertexArray()
{
glDeleteVertexArrays(1, &_objectId);
}
//Bind/Unbind
void bind(void) const override { glBindVertexArray(_objectId); }
void unbind(void) const override { glBindVertexArray(0); }
void bindAttribute(Buffer vertexBuffer, GLuint index, GLint size, GLenum type, GLboolean normalized, GLsizei stride, const void * pointer)
{
glBindVertexArray(_objectId);
glBindBuffer(vertexBuffer.getTarget(), vertexBuffer.getId()); //Bind vert buffer before pointing (we need to know which buffer has the pointer)
glVertexAttribPointer(index, size, type, GL_FALSE, stride, pointer);
glEnableVertexAttribArray(index);
glBindBuffer(vertexBuffer.getTarget(), 0); //No need to keep vertex buffer
glBindVertexArray(0);
}
//Bind/Unbind Buffer
void bindBuffer(const Buffer buffer)
{
glBindVertexArray(_objectId);
glBindBuffer(buffer.getTarget(), buffer.getId());
glBindVertexArray(0);
glBindBuffer(buffer.getTarget(), 0);
}
};