Rendering an OpenGL ES 2.0 triangle using QGLWidget in Qt5.3

[codefy]

Hi all.
Actually I am new to both OpenGL ES and Qt.So please don't mind if I go wrong anywhere.
I am trying to render a simple triangle with interpolated vertices.When I compile it shows following errors.

@error: 'initializeGLFunctions' was not declared in this scope
error: 'glGenBuffers' was not declared in this scope
error: 'program' was not declared in this scope
positionID = program.attributeLocation ("s_vPosition");
error: 'glVertexAttribPointer' was not declared in this scope
glVertexAttribPointer(positionID, 3, GL_FLOAT, GL_FALSE, 0, 0);
error: 'glEnableVertexAttribArray' was not declared in this scope
error: 'glBindBuffer' was not declared in this scope
error: 'glBufferData' was not declared in this scope@

In one of the Forums I found that its because of exclusion of GLEW(not sure why it is used).So I went ahead and added #include<GL/glew.h>. But it made the thing worst,I got 121 errors.

This is my code written in Qt Creator. The code below is Geometry.cpp which inherits QGLWidget as Base Class.

@#include "geometry.h"
//#include<GL/glew.h>
#include <QVector3D>
#include <QtOpenGL/QGLFunctions>
#include <QGLShaderProgram>
#include <QtOpenGL/qgl.h>

Geometry::Geometry(QWidget *parent) :
QGLWidget(parent)
{
}

void Geometry::initializeGL()
{
initializeGLFunctions();
glGenBuffers(1, &vbo);
positionID = program.attributeLocation ("s_vPosition");// return the program id which is stored in positionID
colorID= program.attributeLocation("s_vColor");
initTriangleGeometry();
// glewInit();
}

void Geometry::resizeGL(int w, int h)
{
glViewport(0, 0, w, h);
}

void Geometry::paintGL()
{
glClear(GL_COLOR_BUFFER_BIT);

glVertexAttribPointer(positionID, 3, GL_FLOAT, GL_FALSE, 0, 0);
glVertexAttribPointer(colorID, 4, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(3*3*sizeof(GLfloat)));

glEnableVertexAttribArray(positionID);
glEnableVertexAttribArray(colorID);
glDrawArrays(GL_TRIANGLES, 0, 3);

}

void Geometry::initShaders()
{
// Compile vertex shader
if (!program.addShaderFromSourceFile(QGLShader::Vertex, ":/vertexShader.glsl"))
close();

// Compile fragment shader
if (!program.addShaderFromSourceFile(QGLShader::Fragment, ":/fragmen--tShader.glsl"))
    close();

// Link shader pipeline
if (!program.link())
    close();

// Bind shader pipeline for use
if (!program.bind())
    close();

}

void Geometry::initTriangleGeometry()
{
GLfloat vertices[]={-0.5f, -0.5f, 0.0f,
0.5f, -0.5f, 0.0f,
0.0f, 0.5f, 0.0f};

GLfloat colors[]={1.0f, 0.0f, 0.0f, 1.0f,
                   0.0f, 1.0f, 0.0f, 1.0f,
                   0.0f, 0.0f, 1.0f, 1.0f};


glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, 7*3*sizeof(GLfloat), NULL, GL_STATIC_DRAW);
glBufferSubData(GL_ARRAY_BUFFER, 0, 3*3*sizeof(GLfloat), vertices);
glBufferSubData(GL_ARRAY_BUFFER, 3*3*sizeof(GLfloat),3*4*sizeof(GLfloat), colors);

}
@

Main.cpp

@#include "mainwindow.h"
#include <QApplication>
#include <geometry.h>

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
a.setApplicationName("Triangle");
Geometry widget;
widget.showMaximized();

return a.exec();

}@

Vertex Shader:

@attribute vec3 s_vPosition;
attribute vec4 s_vColor;
varying vec4 color;

void main () {
color = s_vColor;
gl_Position = vec4(s_vPosition, 1.0);
}@

Fragmnet Shader:
@varying vec4 color;

void main () {
gl_FragColor = color;
}@

Please Help.

[Ferobles92]

codefy,
the following link is to a youtube video of someone doing exactly what you want
https://www.youtube.com/watch?v=1nzHSkY4K18

however, I encourage you to look into QWindow. As I understand, the Qt project is trying to move away from the QGLWidget. They want to use QWindow only. Use createWindowContainer() on your MainWindow class to create a drawable OpenGL surface, the QWindow.

Hope this works.

[SGaist]

Hi,

No they are not, QGLWidget will have a replacement called QOpenGLWidget.

[codefy]

Thank you both of you for your reply.

Ferobles,
Actually I have referred this video before it is to render a triangle using fixed rendering pipeline but I want to do it using programmable pipeline.What about the Error any idea?

SGaist,
What does that mean can you please explain it precisely?

[sierdzio]

A new, better class will be introduced in Qt 5.4 (alpha version will be available this week, or early next week): QOpenGLWidget. You can read some discussion about it here: "link":http://comments.gmane.org/gmane.comp.lib.qt.devel/17852.

[agocs]

You are most likely not deriving from QGLFunctions, hence the absence of initializeGLFunctions and the GL2 stuff. The Geometry class should derive both from QGLWidget and QGLFunctions:
class Geometry : public QGLWidget, protected QGLFunctions { ... };

[jiangcaiyang]

According to Qt's roadmap, Qt 5.4 will have all QGL* classes and functions deprecated. Try using QOpenGL* classes instead.

[codefy]

Thanks all for commenting here.

agocs,
Why we need multiple inheritance.?How will it solve my problems?

sierdzio,
That really was an useful information.

jiangcaiyang,
I tried it but no luck. Seems like Qt5.3.1 does not supports it.Not sure.