OpenGL rendering textured quad as a single pixel at (0,0)? - c++

Question

I have a renderer2D that is very basic but doesn't render my basic 2D quad correctly. It renders it as a single pixel at the bottom left of the window. The window size is 800x600
The orthographic projection matrices are calculated using glm::ortho(0.0f, 800.0f, 0.0f, 600.0f).
For some reason it only renders a single pixel at the wrong location. And to make it even more weirder, If i set the Model Matrix to translate to the middle of the screen, It renders that lone pixel at the middle of the screen
I call it like this in my renderer class :
m_Renderer2D.RenderQuad(glm::vec3(400.0f, 300.0f, 1.0f), &m_CrosshairTexture, &m_Camera2D);
Renderer class :
class Renderer2D
{
public:
Renderer2D();
void RenderQuad(const glm::vec2& position, GLClasses::Texture* texture, OrthographicCamera* camera);
private :
GLClasses::VertexBuffer m_VBO;
GLClasses::VertexArray m_VAO;
GLClasses::IndexBuffer m_IBO;
GLClasses::Shader m_DefaultShader;
};
cpp file :
Renderer2D::Renderer2D() : m_VBO(GL_ARRAY_BUFFER)
{
GLuint index_buffer[6] = { 0,1,2,2,3,0 };
m_VAO.Bind();
m_VBO.Bind();
m_IBO.Bind();
m_VBO.VertexAttribPointer(0, 3, GL_FLOAT, 0, 5 * sizeof(GLfloat), (void*)0);
m_VBO.VertexAttribPointer(0, 2, GL_FLOAT, 0, 5 * sizeof(GLfloat), (void*)(3 * sizeof(GLfloat)));
m_IBO.BufferData(6 * sizeof(GLuint), index_buffer, GL_STATIC_DRAW);
m_VAO.Unbind();
m_DefaultShader.CreateShaderProgramFromFile("Shaders/2DElementShaderVert.glsl", "Shaders/2DElementShaderFrag.glsl");
m_DefaultShader.CompileShaders();
}
void Renderer2D::RenderQuad(const glm::vec2& position, GLClasses::Texture* texture, OrthographicCamera* camera)
{
glDisable(GL_DEPTH_TEST);
const std::array<GLfloat, 8> texture_coords = texture->GetTextureCoords();
float x, y, w, h;
x = position.x;
y = position.y;
w = position.x + texture->GetWidth(); // The width and height of the texture is correct
h = position.y + texture->GetHeight();
GLfloat Vertices[] = {
w, y, 0.0f, texture_coords[0], texture_coords[1],
w, h, 0.0f, texture_coords[2], texture_coords[3],
x, h, 0.0f, texture_coords[4], texture_coords[5],
x, y, 0.0f, texture_coords[6], texture_coords[7],
};
m_DefaultShader.Use();
glm::mat4 proj = glm::ortho(0.0f, 800.0f, 0.0f, 600.0f);
texture->Bind(1);
m_DefaultShader.SetMatrix4("u_Projection", proj, 0);
m_DefaultShader.SetMatrix4("u_View", camera->GetViewMatrix(), 0);
m_DefaultShader.SetMatrix4("u_Model", glm::mat4(1.0f), 0);
m_DefaultShader.SetInteger("u_Texture", 1, 0);
// Draw the 2D quad
m_VAO.Bind();
m_VBO.BufferData(20 * sizeof(GLfloat), Vertices, GL_STATIC_DRAW);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, (void*)0);
m_VAO.Unbind();
glEnable(GL_DEPTH_TEST);
}
Shaders :
VERTEX SHADER :
#version 330 core
layout(location = 0) in vec3 a_Position;
layout(location = 1) in vec2 a_TexCoord;
out vec2 v_TexCoord;
uniform mat4 u_Projection;
uniform mat4 u_View;
uniform mat4 u_Model;
void main()
{
gl_Position = u_Projection * u_View * u_Model * vec4(a_Position, 1.0f);
v_TexCoord = a_TexCoord;
}
FRAGMENT SHADER :
#version 330 core
in vec2 v_TexCoord;
out vec4 o_Color;
uniform sampler2D u_Texture;
void main()
{
o_Color = texture(u_Texture, v_TexCoord);
}

Answer 1

The layout locations associate the vertex coordinates to attribute index 0 and the texture coordinates to attribute index 1:
layout(location = 0) in vec3 a_Position;
layout(location = 1) in vec2 a_TexCoord;
When you specify the arrays of generic vertex attribute data, then the vertex attribute array 0 is specified twice, but you missed to specify the vertex attribute array 1:
m_VBO.VertexAttribPointer(0, 3, GL_FLOAT, 0, 5 * sizeof(GLfloat), (void*)0);
m_VBO.VertexAttribPointer(0, 2, GL_FLOAT, 0, 5 * sizeof(GLfloat), (void*)(3 * sizeof(GLfloat)));
Hence the texture coordinates cover the vertex coordinates and the texture coordinate attribute is not specified at all.
The attribute index for the texture coordinates has to be 1 rather than 0:
m_VBO.VertexAttribPointer(0, 2, GL_FLOAT, 0, 5 * sizeof(GLfloat), (void*)(3 * sizeof(GLfloat)));
m_VBO.VertexAttribPointer(1, 2, GL_FLOAT, 0, 5 * sizeof(GLfloat), (void*)(3 * sizeof(GLfloat)));