OpenGL line width/thickness

[thompsonx]

Hi,
I am trying to draw a skeleton of a cube (i.e. edges) in OpenGL. I have an array of all edges (lines) which are specified by two vertices. Everything is ok. I am able to render a wireframed cube. Nevertheless, I would like to have thicker lines and I tried to do it by glLineWidth but it does not work. Have you any idea what I am doing wrong?

thx

#include "model3.h"

#include <QDebug>
#include <QtMath>

Model3::Model3(QWidget* parent) : QOpenGLWidget(parent)
{

}

Model3::~Model3()
{
    delete m_program;
}


void Model3::initializeGL()
{
    this->initializeOpenGLFunctions();

    const char* clickVertexShader =
            "#version 330 core\n"
            "uniform mat4 projection;\n"
            "uniform mat4 view;\n"
            "uniform mat4 model;\n"
            "in vec4 position;\n"
            "void main()\n"
            "{\n"
            "gl_Position = projection * view * model * position;"
            "}\n";
    const char* clickFragmentShader =
            "#version 330\n"
            "out vec4 outputF;\n"
            "void main()\n"
            "{\n"
            "outputF = vec4(0, 0, 0, 0);"
            "}\n";

    this->m_program = new QOpenGLShaderProgram(this);
    m_program->addShaderFromSourceCode(QOpenGLShader::Vertex, clickVertexShader);
    m_program->addShaderFromSourceCode(QOpenGLShader::Fragment, clickFragmentShader);
    m_program->link();
    m_aPos = m_program->attributeLocation("position");

    glEnable(GL_DEPTH_TEST);

    this->m_lastX = width() / 2;
    this->m_lastY = height() / 2;
}


void Model3::resizeGL(int, int)
{

}


void Model3::paintGL()
{
    glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    this->m_program->bind();

    float lines[] = {
        -0.5f, -0.5f,  0.5f,  0.5f, -0.5f,  0.5f,

        -0.5f, -0.5f,  0.5f, -0.5f,  0.5f,  0.5f,

        -0.5f, -0.5f,  0.5f, -0.5f, -0.5f, -0.5f,

         0.5f, -0.5f,  0.5f,  0.5f,  0.5f,  0.5f,

         0.5f, -0.5f,  0.5f,  0.5f, -0.5f, -0.5f,

         0.5f, -0.5f, -0.5f, -0.5f, -0.5f, -0.5f,

         0.5f, -0.5f, -0.5f,  0.5f,  0.5f, -0.5f,

        -0.5f, -0.5f, -0.5f, -0.5f,  0.5f, -0.5f,

        -0.5f,  0.5f,  0.5f,  0.5f,  0.5f,  0.5f,

        -0.5f,  0.5f,  0.5f, -0.5f,  0.5f, -0.5f,

         0.5f,  0.5f,  0.5f,  0.5f,  0.5f, -0.5f,

         0.5f,  0.5f, -0.5f, -0.5f,  0.5f, -0.5f
    };

    QVector<QVector3D> cubePositions;
    cubePositions << QVector3D(0.0f,  0.0f,  0.0f);

    QMatrix4x4 view;
    view.translate(0.0f, 0.0f, -3.0f);
    view.rotate(45.0f, 1.0f, 0.0f, 0.0f);
    view.rotate(45.0f, 0.0f, 1.0f, 0.0f);

    QMatrix4x4 projection;
    projection.perspective(m_fov, (float)width() / (float)height(), 0.1f, 100.0f);

    m_program->setUniformValue("projection", projection);

    QOpenGLBuffer vbo(QOpenGLBuffer::VertexBuffer);
    vbo.create();
    vbo.bind();
    vbo.setUsagePattern(QOpenGLBuffer::StaticDraw);
    vbo.allocate(lines, sizeof(lines));

    m_program->setUniformValue("view", view);

    QOpenGLVertexArrayObject cubeVAO(this);
    cubeVAO.create();
    cubeVAO.bind();

    glVertexAttribPointer(m_aPos, 3, GL_FLOAT, GL_FALSE, 3*sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    QMatrix4x4 model;
    model.translate(cubePositions[0]);
    m_program->setUniformValue("model", model);

    glLineWidth(5.0f);

    for (int l = 0; l < 24; l += 2)
    {
        glDrawArrays(GL_LINES, l, 2);
    }

    glDisableVertexAttribArray(0);

    cubeVAO.release();

    vbo.release();

    m_program->release();
}


void Model3::wheelEvent(QWheelEvent *event)
{
    float sign = (event->angleDelta().y() > 0) ? 1.0f : -1.0f;

    if (m_fov >= 1.0f && m_fov <= 45.0f)
        m_fov -= sign * 3;

    if (m_fov <= 1.0f)
        m_fov = 1.0f;

    if (m_fov >= 45.0f)
        m_fov = 45.0f;

    this->update();
}

[m.sue]

Hi @thompsonx

Maybe your OpenGL card does not support it: https://stackoverflow.com/questions/34866964/opengl-gllinewidth-doesnt-change-size-of-lines

-Michael.

[thompsonx]

thx @m-sue for reply

It might not be the problem. I have tried to print the GL_ALIASED_LINE_WIDTH_RANGE variable and it shows interval (1, 7.375).

[m.sue]

Hi @thompsonx

Maybe you will need glEnable(GL_LINE_SMOOTH);?

-Michael

[thompsonx]

@m.sue

No effect

 glEnable(GL_LINE_SMOOTH);
    glLineWidth(5.0f);
    GLfloat lineWidthRange[2] = {0.0f, 0.0f};
    glGetFloatv(GL_ALIASED_LINE_WIDTH_RANGE, lineWidthRange);
    qInfo() << lineWidthRange[0] << lineWidthRange[1];

    for (int l = 0; l < 24; l += 2)
    {
        m_program->setUniformValue("code", l);
        glDrawArrays(GL_LINES, l, 2);
    }

[YuCrazing]

Anyone solved this problem? I have the same problem, the range of supported line widths is:
GL_ALIASED_LINE_WIDTH_RANGE: (1.0, 10.0)
GL_SMOOTH_LINE_WIDTH_RANGE: (1.0, 1.0)