LINUX环境下QT5.9+OPENGL绘制图形与渲染入门（四）

 

Q_OBJECT
public:
PaintingWidget(QWidget *parent = nullptr);
~PaintingWidget();

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

private:
QOpenGLBuffer *m_vbo, *m_cbo;
QOpenGLVertexArrayObject *m_vao;
QOpenGLShaderProgram *m_shader;
float aspectRatio;
GLfloat colorBuffer[4 * 3 * 3];
GLfloat vertexData[4 * 3 * 3];
};
#endif // PAINTINGWIDGET_H

4.修改mainwindow.cpp
#include “mainwindow.h”
MainWindow::MainWindow(QWidget *parent)
: QWidget(parent)
{
m_layout = new QVBoxLayout(this);
setLayout(m_layout);
m_painting = new PaintingWidget(this);
m_layout->addWidget(m_painting);
}

MainWindow::~MainWindow()
{
}

5.修改paintingwidget.cpp
#include “paintingwidget.h”
static const char* VERTEX_SHADER_CODE =
“#version 330 \n”
“layout(location = 0) in vec3 posVertex;\n”
“layout(location = 1) in vec3 colVertex;\n”
“uniform mat4 MVP;\n”
“out vec4 cols;\n”
“void main() {\n”
" gl_Position = MVP * vec4(posVertex, 1.0f);\n"
" cols = vec4(colVertex, 1.0f);\n"
“}\n”;

static const char* FRAGMENT_SHADER_CODE =
“#version 330\n”
“in vec4 cols;\n”
“out vec4 fragColor;\n”
“void main() {\n”
" fragColor = cols;\n"
“}\n”;

6.编写mainwindow.cpp函数实现
PaintingWidget::PaintingWidget(QWidget *parent) :
QOpenGLWidget (parent), m_vbo(nullptr), m_vao(nullptr), m_shader(nullptr)
{
const GLfloat VERTEX_INIT_DATA[] =
{
//face 1
-0.5f, 0.0f,-0.2887f,
0.5f, 0.0f,-0.2887f,
0.0f, 0.0f, 0.5774f,
//face 2
-0.5f, 0.0f,-0.2887f,
0.5f, 0.0f,-0.2887f,
0.0f, 0.8165f, 0.0f,
//face 3
-0.5f, 0.0f,-0.2887f,
0.0f, 0.0f, 0.5774f,
0.0f, 0.8165f, 0.0f,
//face 4
0.5f, 0.0f,-0.2887f,
0.0f, 0.0f,0.5774f,
0.0f, 0.8165f, 0.0f,
};

const GLfloat COLOR_INIT_DATA[] =
{
    1.0f, 0.0f, 0.0f,
    1.0f, 0.0f, 0.0f,
    1.0f, 0.0f, 0.0f,
    0.0f, 1.0f, 0.0f,
    0.0f, 1.0f, 0.0f,
    0.0f, 1.0f, 0.0f,
    0.0f, 0.0f, 1.0f,
    0.0f, 0.0f, 1.0f,
    0.0f, 0.0f, 1.0f,
    1.0f, 0.0f, 1.0f,
    1.0f, 0.0f, 1.0f,
    1.0f, 0.0f, 1.0f,
};
memcpy(this->vertexData, VERTEX_INIT_DATA, sizeof(this->vertexData));
memcpy(this->colorBuffer, COLOR_INIT_DATA, sizeof(this->colorBuffer));
aspectRatio = (float) 800/600;

}

PaintingWidget::~PaintingWidget()
{

}

void PaintingWidget::initializeGL()
{
QOpenGLFunctions *f = this->context()->functions();
f->glEnable(GL_DEPTH_TEST);
m_shader = new QOpenGLShaderProgram();
m_shader->addShaderFromSourceCode(QOpenGLShader::Vertex, VERTEX_SHADER_CODE);
m_shader->addShaderFromSourceCode(QOpenGLShader::Fragment, FRAGMENT_SHADER_CODE);

if(m_shader->link())
{
    qDebug("Shaders link success");

}
else
{
    qDebug("Shaders link failed!");
}

m_vao = new QOpenGLVertexArrayObject();
m_vbo = new QOpenGLBuffer(QOpenGLBuffer::Type::VertexBuffer);
m_cbo = new QOpenGLBuffer(QOpenGLBuffer::Type::VertexBuffer);

m_vao->create();
m_vao->bind();
m_vbo->create();
m_vbo->bind();

m_vbo->allocate(this->vertexData, 4 * 3 * 3 * sizeof(GLfloat));
f->glEnableVertexAttribArray(0);
f->glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3*sizeof(GLfloat), 0);
m_vbo->release();
m_cbo->create();
m_cbo->bind();

m_cbo->allocate(this->colorBuffer, 4*3*3*sizeof(GLfloat));
f->glEnableVertexAttribArray(1);
f->glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 3*sizeof (GLfloat), 0);
m_cbo->release();
m_vao->release();

}

void PaintingWidget::paintGL()
{
QOpenGLFunctions *f = this->context()->functions();
f->glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
f->glClearColor(0.0f, 0.2f, 0.0f, 1.0f);
m_vao->bind();
m_shader->bind();
QMatrix4x4 mvp;
mvp.perspective(45.0f, this->aspectRatio, 0.1f, 100.0f);
mvp.lookAt(QVector3D(0.0f, 3.0f, 0.0f), QVector3D(0.0f, 0.0f, 0.0f), QVector3D(1.0f, 0.0f, 0.0f));

m_shader->setUniformValue(m_shader->uniformLocation("MVP"), mvp);
f->glDrawArrays(GL_TRIANGLES, 0, 4*3);
m_shader->release();
m_vao->release();

}

void PaintingWidget::resizeGL(int w, int h)
{
aspectRatio = (float)w / h;
}

本篇博客重点在于入门QT+OpenGL，基本图形绘制，避免刚入门同学走许多不必要的大坑，代码全部公开，仅供参考，如有错误请指正。