Why is color displayed instead of texture in open gl?

Question

Qt

I have a cube on stage. I draw a texture on it. But instead of the texture, only the green color is shown.
Please tell me how to fix.

I bring my code.

Vertex shader

attribute vec4 a_position;
attribute vec2 a_textcoord;
attribute vec3 a_normal;
uniform mat4 projectionMatrix;
uniform mat4 modelMatrix;
uniform mat4 viewMatrix;
varying vec4 v_position;
varying vec2 vTexcoord;
varying vec3 v_normal;

void main(void)
{
    mat4 mvMatrix = viewMatrix * modelMatrix;
    gl_Position = projectionMatrix * mvMatrix * a_position;

    vTexcoord = a_textcoord;
    v_normal = normalize(vec3(mvMatrix * vec4(a_normal , 0.0)));
    v_position = mvMatrix * a_position;
}

fragment shader

uniform sampler2D u_texture;
varying vec4 v_position;
varying vec2 v_texcoord;
varying vec3 v_normal;

void main(void)
{
    gl_FragColor = texture2D(u_texture, v_texcoord);
}

Main code

#include "mainwindow.h"

#include <QApplication>
#include <QMessageBox>

MainWindow::MainWindow(QWidget *parent) :
    QOpenGLWidget(parent),
    m_texture(nullptr),
    m_vertexBuffer(QOpenGLBuffer::VertexBuffer),
    m_indexBuffer(QOpenGLBuffer::IndexBuffer){


}

MainWindow::~MainWindow()
{

}

void MainWindow::initializeGL()
{
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);

    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);

    Scene1();
}


void MainWindow::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    QMatrix4x4 ViewMatrix;
    ViewMatrix.setToIdentity();
    ViewMatrix.translate(0.0f, 0.0f, -5.0f);
    QMatrix4x4 modelmatrix;
    modelmatrix.setToIdentity();
    m_texture->bind(0);

    m_shaderProgramm.bind();
    m_shaderProgramm.setUniformValue("projectionMatrix", m_projectionMatrix);
    m_shaderProgramm.setUniformValue("viewMatrix", ViewMatrix);
    m_shaderProgramm.setUniformValue("modelMatrix", modelmatrix);
    m_shaderProgramm.setUniformValue("u_texture", 0);


    // Bind buffers
    m_vertexBuffer.bind();
    m_indexBuffer.bind();

    int offset = 0;

    int location = m_shaderProgramm.attributeLocation("a_position");
    m_shaderProgramm.enableAttributeArray(location);
    m_shaderProgramm.setAttributeBuffer(location, GL_FLOAT, offset, 3, sizeof(VertexData));

    offset += sizeof(QVector3D);

    location = m_shaderProgramm.attributeLocation("vTexcoord");
    m_shaderProgramm.enableAttributeArray(location);
    m_shaderProgramm.setAttributeBuffer(location, GL_FLOAT, offset, 2, sizeof(VertexData));



    glDrawElements(GL_TRIANGLES, m_indexBuffer.size(), GL_UNSIGNED_INT, 0);

}

void MainWindow::Scene1()
{
    initShaders();
    initCube();
}

void MainWindow::initShaders()
{
    if (!m_shaderProgramm.addShaderFromSourceFile(QOpenGLShader::Vertex, "://vshader.vsh"))
        close();

    if (!m_shaderProgramm.addShaderFromSourceFile(QOpenGLShader::Fragment, "://fshader.fsh"))
        close();

    if (m_shaderProgramm.link())
        close();

    if (!m_shaderProgramm.bind())
        close();

}

void MainWindow::initCube()
{
    float width_div_2 =1;
    QVector<VertexData> vertexes;


    //front, right, top, back, left, down

тут геометрия куба

    //front, right, top, back, left, down

    QVector<GLuint> indexes;
    for (int i = 0; i < 24; i += 4){
        indexes.append(i + 0);
        indexes.append(i + 1);
        indexes.append(i + 2);
        indexes.append(i + 2);
        indexes.append(i + 1);
        indexes.append(i + 3);
    }

    // Create and fill vertex buffer and then -> release
    m_vertexBuffer.create();
    m_vertexBuffer.bind();
    m_vertexBuffer.allocate(vertexes.constData(), vertexes.size() * sizeof(VertexData));
    m_vertexBuffer.release();

    // Create and fill index buffer and then -> release
    m_indexBuffer.create();
    m_indexBuffer.bind();
    m_indexBuffer.allocate(indexes.constData(), indexes.size() * sizeof(GLuint));
    m_indexBuffer.release();

    m_texture = new QOpenGLTexture(QImage("://cube.jpg").mirrored());
    m_texture->setMinificationFilter(QOpenGLTexture::Nearest);
    m_texture->setMagnificationFilter(QOpenGLTexture::Linear);
    m_texture->setWrapMode(QOpenGLTexture::Repeat);
}

Answer 1

variables of type varuing are passed from the vertex shader to the fragment shader and they are only read in the fragment one! Here is the link https://ru.stackoverflow.com/questions/766483/glsl ...