How to write 3D applications?

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Good, let's render a green triangle on our blue background. Our triangle has 3 vertices:

std::array<float, 3 * 2> m_vertices = {{ // 3 vertices * 2 coordinates
    -0.75f, -0.75f, // vertex 1 : x, y
    -0.75f,  0.75f, // vertex 2 : x, y
     0.75f,  0.75f  // vertex 3 : x, y
}};

We only give x and y coordinates here. We'll assume that z is zero and w is one. Also we don't provide any color information here as we'll assume that the triangle is uniformly green.

That's the data we'll feed to our OpenGL program. The program consists of two parts, both written in GLSL (= OpenGL Shading Language): a vertex shader and a fragment shader:

shader.vert

#version 330
in vec2 position;

void main() {
  gl_Position = vec4(position, 0.0, 1.0); // x, y, z, w
}

shader.frag

#version 330
out vec4 color;

void main() {
   color = vec4(0.0, 1.0, 0.0, 1.0); // red, green, blue, alpha ; our triangle will be green
}

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And now we put all that together and get this:

my3dwidget.h

#ifndef MY3DWIDGET_H
#define MY3DWIDGET_H

#include <QOpenGLWidget>
#include <QOpenGLFunctions>
#include <array>
#include <QOpenGLShaderProgram>
#include <QOpenGLBuffer>
#include <QOpenGLVertexArrayObject>

class My3dWidget
        : public QOpenGLWidget
        , protected QOpenGLFunctions
{
    Q_OBJECT
public:
    explicit My3dWidget(QWidget *parent = nullptr);

protected:
    virtual void initializeGL() override;
    virtual void resizeGL(int w, int h) override;
    virtual void paintGL() override;

private:
    std::array<float, 3 * 2> m_vertices = {{ // 3 vertices * 2 coordinates
        -0.75f, -0.75f, // vertex 1 : x, y
        -0.75f,  0.75f, // vertex 2 : x, y
         0.75f,  0.75f  // vertex 3 : x, y
    }};

    QOpenGLShaderProgram m_program;
    QOpenGLBuffer m_buffer;
    QOpenGLVertexArrayObject m_vao;
};

#endif // MY3DWIDGET_H

my3dwidget.cpp

#include "my3dwidget.h"

My3dWidget::My3dWidget(QWidget *parent)
    : QOpenGLWidget(parent)
{
}

void My3dWidget::initializeGL()
{
    initializeOpenGLFunctions();
    glClearColor(0.0f, 0.0f, 1.0f, 1.0f); // blue

    m_program.addShaderFromSourceFile(QOpenGLShader::Vertex, ":/shaders/shader.vert");
    m_program.addShaderFromSourceFile(QOpenGLShader::Fragment, ":/shaders/shader.frag");
    m_program.link();
    m_program.bind();

    m_buffer.create();
    m_buffer.bind();
    m_buffer.allocate(m_vertices.data(), // pointer to first element of array
                      sizeof(m_vertices)); // size of array in bytes

    m_vao.create();
    m_vao.bind();
    m_program.enableAttributeArray(0); // vertex array at location 0
    m_program.setAttributeBuffer(0, // location 0
                                 GL_FLOAT, // elements of the array are of type GL_FLOAT (= float)
                                 0, // start at array position 0
                                 2, // number of elements per vertex (= x, y)
                                 0); // stride: densely packed (= no holes)

    m_vao.release();
    m_buffer.release();
    m_program.release();
}

void My3dWidget::resizeGL(int w, int h)
{
    Q_UNUSED(w)
    Q_UNUSED(h)
}

void My3dWidget::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT);
    m_program.bind();
    m_vao.bind();
    glDrawArrays(GL_TRIANGLES, 0, sizeof(m_vertices));
    m_vao.release();
    m_program.release();
}

End of tutorial.

parvizwpf

very very thanks friend.
so why i could not run qt 5 tutorial? link text
what about GLUT? can i use glut commands in Qt?
can i ask my questions if i had more on future?
UPDATED:
i can to run trent reed tutorial finally. of course in my laptop. but on my work pc not run. that get erros: ~~link text~~

[Edit: removed link, contains malware ~~ @Wieland]

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@parvizwpf said in How to write 3D applications?:

very very thanks friend

No worries. Please mark the thread as solved and vote-up the posts that were helpful.

can i ask my questions if i had more on future

Sure. Please start a new thread for each specific question.

i can to run it of course in my laptop. but on my work pc not run. that get erros: link text

The domain you linked to contains malware. Please use a different image hoster, e.g. http://postimages.org/

parvizwpf

repaired error image link
what about GLUT? can i use glut commands in Qt?
whatever you help me to start opengl :-)))
"vote-up the posts that were helpful." how?

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GLUT is old and stinks. You don't want to touch it.

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@parvizwpf said in How to write 3D applications?:

"vote-up the posts that were helpful." how?

see https://forum.qt.io/topic/71830

parvizwpf

why? i see it in many web tutorials.

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@parvizwpf said in How to write 3D applications?:

why? i see it in many web tutorials

because all these tutorials are outdated and written by n00bs

parvizwpf

i can not see anything in your topic link.
how can i create a quote? i don't see it.
n00bs???? if those are n00bs ,so who am i?
do you tell me good tutorials ?

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Edit: Oops, looks like you've been faster :-)

parvizwpf

[????????]

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but on my work pc not run.

Maybe your PC has a terribly outdated GPU or the driver has some problem.

do you tell me good tutorials ?

Actually I like Trent's tutorial for the Qt integration part. Anything else: get a book on GLSL.

parvizwpf

@Wieland
maybe. you right.
Good luck.