Open GL ES 2.0 Why is my VBO not working? - c++

Question

Hey there Im trying to draw a simple quad with 2 triangles in OpenGL through a vbo.
However I have looked at my code multiple times and I don't see what I am missing.
I ain't no Open GL expert, The code was working fine without any buffers however when I switchted to VBO Im not seeing anything anymore. OpenGL also doesn't provide any helpfull errors.
Image::Image(Graphics * GFX)
{
glm::vec2 corners[2];
corners[0] = glm::vec2(0, 0);
corners[1] = glm::vec2(1, 1);
vertices = new GLfloat[30]
{
//Vertices XYZ TexCoord X,Y
corners[0].x, corners[0].y, 0.0f, 0,0,
corners[0].x, corners[1].y, 0.0f, 0,1,
corners[1].x, corners[0].y, 0.0f, 1,0,
corners[1].x,corners[1].y,0.0f, 1,1,
corners[0].x, corners[1].y,0.0f, 0,1,
corners[1].x, corners[0].y, 0.0f, 1,0
};
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
//Setting up some stuff
const char *vertexShaderSource =
"attribute vec4 vPosition; \n"
"attribute vec2 vTexCoord; \n"
"void main() \n"
"{ \n"
" gl_Position = vPosition; \n"
"} \n";
const char *fragmentShaderSource =
"precision mediump float; \n"
"void main() \n"
"{ \n"
" gl_FragColor = vec4(1.0, 1.0, 1.0, 1.0); \n"
"} \n";
// Load and compile the vertex/fragment shaders
vertexShader = GFX->LoadShader(GL_VERTEX_SHADER, (const char*)vertexShaderSource);
fragmentShader = GFX->LoadShader(GL_FRAGMENT_SHADER, (const char*)fragmentShaderSource);
// Create the program object
programObject = glCreateProgram();
// now we have the V and F shaders attach them to the progam object
glAttachShader(programObject, vertexShader);
glAttachShader(programObject, fragmentShader);
// Link the program
glLinkProgram(programObject);
// Check the link status
// Link the program
GLint AreTheylinked;
glGetProgramiv(programObject, GL_LINK_STATUS, &AreTheylinked);
if (!AreTheylinked)
{
GLint RetinfoLen = 0;
// check and report any errors
glGetProgramiv(programObject, GL_INFO_LOG_LENGTH, &RetinfoLen);
if (RetinfoLen > 1)
{
GLchar* infoLog = (GLchar*)malloc(sizeof(char) * RetinfoLen);
glGetProgramInfoLog(programObject, RetinfoLen, NULL, infoLog);
fprintf(stderr, "Error linking program:\n%s\n", infoLog);
free(infoLog);
}
glDeleteProgram(programObject);
}
positionLocation = glGetAttribLocation(programObject, "vPosition");
textureCoordLocation = glGetAttribLocation(programObject, "vTexCoord");
if (glGetError() == GL_NO_ERROR) {}
else
printf("Init failed!\n");
//End setting up
}
Image::~Image()
{
}
void Image::Draw()
{
std::cout << "Calling Draw on Image" << std::endl;
glUseProgram(programObject);
glEnable(GL_DEPTH_TEST);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
GLsizei stride = (5) * sizeof(GLfloat);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, stride, 0);
glEnableVertexAttribArray(0);
glDrawArrays(GL_TRIANGLES, 0, 6);
if (glGetError() != GL_NO_ERROR)
{
printf("UI Draw error\n");
}
glDisableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
}
And how I am loading the shaders:
GLuint Graphics::LoadShader(GLenum type, const char *shaderSrc)
{
// 1st create the shader object
GLuint TheShader = glCreateShader(type);
if (TheShader == 0) return FALSE; // can't allocate so stop.
// pass the shader source then compile it
glShaderSource(TheShader, 1, &shaderSrc, NULL);
glCompileShader(TheShader);
GLint IsItCompiled;
// After the compile we need to check the status and report any errors
glGetShaderiv(TheShader, GL_COMPILE_STATUS, &IsItCompiled);
if (!IsItCompiled)
{
GLint RetinfoLen = 0;
glGetShaderiv(TheShader, GL_INFO_LOG_LENGTH, &RetinfoLen);
if (RetinfoLen > 1)
{ // standard output for errors
char* infoLog = (char*)malloc(sizeof(char) * RetinfoLen);
glGetShaderInfoLog(TheShader, RetinfoLen, NULL, infoLog);
fprintf(stderr, "Error compiling this shader:\n%s\n", infoLog);
free(infoLog);
}
glDeleteShader(TheShader);
return FALSE;
}
return TheShader;
}
It worked fine without a buffer previously, and saw a white square by using:
glVertexAttribPointer(0, 6, GL_FLOAT, GL_FALSE, 0, vertices);
But now I want to add texture coordinates to my quad through a VBO but nothing shows anymore.
Smoothy101

Answer 1

Your buffer creation looks fine - the problem is your attribute pointer setup. You've added texture coordinates which has changed data layout for each vertex, but you've not handled that in your code.
You need something like this:
glVertexAttribPointer(positionLocation, 3, GL_FLOAT, GL_FALSE, stride, 0);
glVertexAttribPointer(textureCoordLocation, 2, GL_FLOAT, GL_FALSE, stride, 8);
... not this:
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, stride, 0);