[英]How to draw triangles in Qt6 using QOpenGLWidget?
引用一个 7 岁的问题: 如何在 QOpenGLWidget 中渲染三角形?
此处接受的答案对如何设置示例进行了非常详细的解释,但是由于对该答案 state (几年后)的大量评论,示例中的某些部分已被弃用或不再是最佳实践。
任何人都可以在 Qt6+ 中解释如何在不使用 glBegin/glEnd 且不使用 GLU 的情况下执行此操作吗?
我最终需要能够围绕 OpenGL 上下文构建 GUI,OpenGL 能够将 3D 模型渲染为线框,无需任何类型的着色器或纹理映射到它。
我尝试从多维数据集示例开始工作。 我能够添加 GUI 元素,但它们呈现在 OpenGL window 之上,而不是在它之上或周围,我不确定如何更改代码来解决这个问题。 我能够从文件中输入 3D 几何图形并将其获取到 plot ,但是它将示例中的 cube.png 纹理映射到任何东西上质地。
编辑以添加示例图像和 C++ 代码:
Edit2:添加 GLPolygonMode 后(反映在下面的代码中)
主文件
#include <QApplication>
#include <QLabel>
#include <QSurfaceFormat>
#ifndef QT_NO_OPENGL
#include "mainwidget.h"
#endif
#include "geometryengine.h"
#include "storedGeometry.h"
extern "C" {
// this fortran function is called by cpp
void rk_viz_f90(const char *geoname, int str_len=0); // length is optional, default 0, pass by value
// this cpp function is called by fortran
void send_facet(float in[][3])
{
gUseGeom.addFacet(GeometryEngine::facetData(QVector3D(in[0][0],in[0][1],in[0][2]),QVector3D(in[1][0],in[1][1],in[1][2]),QVector3D(in[2][0],in[2][1],in[2][2])));
}
}
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QSurfaceFormat format;
format.setDepthBufferSize(24);
QSurfaceFormat::setDefaultFormat(format);
app.setApplicationName("cube");
app.setApplicationVersion("0.1");
// Call Fortran Rk_Viz Lib version
std::string geofile = "C:\\TEMP\\qt\\demo_send_arrays\\sphere_6in_PW.RawRkViz.bin";
printf("C++ filename %s\n",geofile.c_str());
const char * geoname = geofile.c_str();
rk_viz_f90(geoname,geofile.size());
#ifndef QT_NO_OPENGL
MainWidget widget;
widget.setFixedSize(600,800);
widget.show();
#else
QLabel note("OpenGL Support required");
note.show();
#endif
return app.exec();
}
mainwidget.h
#ifndef MAINWIDGET_H
#define MAINWIDGET_H
#include "geometryengine.h"
#include "storedGeometry.h"
#include <QOpenGLWidget>
#include <QOpenGLFunctions>
#include <QMatrix4x4>
#include <QQuaternion>
#include <QVector2D>
#include <QBasicTimer>
#include <QOpenGLShaderProgram>
#include <QOpenGLTexture>
#include <QPushButton>
class GeometryEngine;
class MainWidget : public QOpenGLWidget, protected QOpenGLFunctions
{
Q_OBJECT
public:
using QOpenGLWidget::QOpenGLWidget;
MainWidget(QWidget *parent = nullptr);
~MainWidget();
protected:
void mousePressEvent(QMouseEvent *e) override;
void mouseReleaseEvent(QMouseEvent *e) override;
void timerEvent(QTimerEvent *e) override;
void initializeGL() override;
void resizeGL(int w, int h) override;
void paintGL() override;
void initShaders();
void initTextures();
private:
std::vector<GeometryEngine::facetData> *pUseGeom = nullptr;
QBasicTimer timer;
QOpenGLShaderProgram program;
GeometryEngine *geometries = nullptr;
QOpenGLTexture *texture = nullptr;
QMatrix4x4 projection;
QVector2D mousePressPosition;
QVector3D rotationAxis;
qreal angularSpeed = 0;
QQuaternion rotation;
QPushButton *loadButton;
};
#endif // MAINWIDGET_H
mainwidget.cpp
#include "mainwidget.h"
#include <QMouseEvent>
#include <QGridLayout>
#include <cmath>
MainWidget::MainWidget(QWidget *parent)
{
// Setup gui by using layout(s), which can be nested
QGridLayout *layout = new QGridLayout;
loadButton = new QPushButton(QString("Load Bin File..."),this);
layout->addWidget(loadButton,0,0,1,1,Qt::AlignHCenter);
}
MainWidget::~MainWidget()
{
// Make sure the context is current when deleting the texture
// and the buffers.
makeCurrent();
delete texture;
delete geometries;
doneCurrent();
}
void MainWidget::mousePressEvent(QMouseEvent *e)
{
// Save mouse press position
mousePressPosition = QVector2D(e->position());
}
void MainWidget::mouseReleaseEvent(QMouseEvent *e)
{
// Mouse release position - mouse press position
QVector2D diff = QVector2D(e->position()) - mousePressPosition;
// Rotation axis is perpendicular to the mouse position difference
// vector
QVector3D n = QVector3D(diff.y(), diff.x(), 0.0).normalized();
// Accelerate angular speed relative to the length of the mouse sweep
qreal acc = diff.length() / 100.0;
// Calculate new rotation axis as weighted sum
rotationAxis = (rotationAxis * angularSpeed + n * acc).normalized();
// Increase angular speed
angularSpeed += acc;
}
void MainWidget::timerEvent(QTimerEvent *)
{
// Decrease angular speed (friction)
angularSpeed *= 0.99;
// Stop rotation when speed goes below threshold
if (angularSpeed < 0.01) {
angularSpeed = 0.0;
} else {
// Update rotation
rotation = QQuaternion::fromAxisAndAngle(rotationAxis, angularSpeed) * rotation;
// Request an update
update();
}
}
void MainWidget::initializeGL()
{
initializeOpenGLFunctions();
glClearColor(0, 0, 0, 1);
initShaders();
initTextures();
// Enable depth buffer
glEnable(GL_DEPTH_TEST);
// Enable back face culling
//glEnable(GL_CULL_FACE);
geometries = new GeometryEngine();
// Use QBasicTimer because its faster than QTimer
timer.start(12, this);
}
void MainWidget::initShaders()
{
// Compile vertex shader
if (!program.addShaderFromSourceFile(QOpenGLShader::Vertex, ":/vshader.glsl"))
close();
// Compile fragment shader
if (!program.addShaderFromSourceFile(QOpenGLShader::Fragment, ":/fshader.glsl"))
close();
// Link shader pipeline
if (!program.link())
close();
// Bind shader pipeline for use
if (!program.bind())
close();
}
void MainWidget::initTextures()
{
// Load cube.png image
texture = new QOpenGLTexture(QImage(":/cube.png").mirrored());
// Set nearest filtering mode for texture minification
texture->setMinificationFilter(QOpenGLTexture::Nearest);
// Set bilinear filtering mode for texture magnification
texture->setMagnificationFilter(QOpenGLTexture::Linear);
// Wrap texture coordinates by repeating
// f.ex. texture coordinate (1.1, 1.2) is same as (0.1, 0.2)
texture->setWrapMode(QOpenGLTexture::Repeat);
}
void MainWidget::resizeGL(int w, int h)
{
// Calculate aspect ratio
qreal aspect = qreal(w) / qreal(h ? h : 1);
// Set near plane to 3.0, far plane to 7.0, field of view 45 degrees
//const qreal zNear = 3.0, zFar = 7.0, fov = 45.0;
const qreal zNear = 0.1, zFar = 10.0, fov = 30.0;
// Reset projection
projection.setToIdentity();
// Set perspective projection
projection.perspective(fov, aspect, zNear, zFar);
}
void MainWidget::paintGL()
{
// Clear color and depth buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
texture->bind();
// Calculate model view transformation
QMatrix4x4 matrix;
matrix.translate(0.0, 0.0, -1);
matrix.rotate(rotation);
// Set modelview-projection matrix
program.setUniformValue("mvp_matrix", projection * matrix);
// Use texture unit 0 which contains cube.png
program.setUniformValue("texture", 0);
// Draw cube geometry
geometries->drawCubeGeometry(&program);
}
几何引擎.h
#ifndef GEOMETRYENGINE_H
#define GEOMETRYENGINE_H
#include <QOpenGLFunctions>
#include <QOpenGLShaderProgram>
#include <QOpenGLBuffer>
class GeometryEngine : protected QOpenGLFunctions
{
public:
struct facetData
{
QVector3D v1;
QVector3D v2;
QVector3D v3;
facetData() {
};
facetData(QVector3D iv1, QVector3D iv2, QVector3D iv3) {
v1 = iv1;
v2 = iv2;
v3 = iv3;
};
~facetData() {
v1.~QVector3D();
v2.~QVector3D();
v3.~QVector3D();
};
};
GeometryEngine();
virtual ~GeometryEngine();
void drawCubeGeometry(QOpenGLShaderProgram *program);
private:
void initCubeGeometry();
QOpenGLBuffer arrayBuf;
QOpenGLBuffer indexBuf;
};
#endif // GEOMETRYENGINE_H
几何引擎.cpp
#include "geometryengine.h"
#include "storedGeometry.h"
#include <QVector2D>
#include <QVector3D>
#include <algorithm>
GeometryEngine::GeometryEngine()
: indexBuf(QOpenGLBuffer::IndexBuffer)
{
initializeOpenGLFunctions();
// Generate 2 VBOs
arrayBuf.create();
indexBuf.create();
// Initializes cube geometry and transfers it to VBOs
initCubeGeometry();
}
GeometryEngine::~GeometryEngine()
{
arrayBuf.destroy();
indexBuf.destroy();
}
void GeometryEngine::initCubeGeometry()
{
// Get a copy of the geometry to reference here
std::vector<GeometryEngine::facetData> tGeom = gUseGeom.getGeom();
// Convert vector to array
GeometryEngine::facetData* aGeom = tGeom.data();
// Get a copy of the generated indices to reference here
std::vector<GLushort> tInd = gUseGeom.getGenIndices();
// Convert vector to array
GLushort* aInd = tInd.data();
// Transfer vertex data to VBO 0
arrayBuf.bind();
arrayBuf.allocate(aGeom, tGeom.size() * sizeof(GeometryEngine::facetData));
// Transfer index data to VBO 1
indexBuf.bind();
indexBuf.allocate(aInd, tInd.size() * sizeof(GLushort));
}
void GeometryEngine::drawCubeGeometry(QOpenGLShaderProgram *program)
{
// Tell OpenGL which VBOs to use
arrayBuf.bind();
indexBuf.bind();
// Tell OpenGL programmable pipeline how to locate vertex position data
int vertexLocation = program->attributeLocation("a_position");
program->enableAttributeArray(vertexLocation);
// setAttributeBuffer(int location, GLenum type, int offset, int tupleSize, int stride = 0)
program->setAttributeBuffer(vertexLocation, GL_FLOAT, 0, 3);
// Tell OpenGL programmable pipeline how to locate vertex texture coordinate data
int texcoordLocation = program->attributeLocation("a_texcoord");
program->enableAttributeArray(texcoordLocation);
// original: program->setAttributeBuffer(texcoordLocation, GL_FLOAT, offset, 2, sizeof(VertexData));
program->setAttributeBuffer(texcoordLocation, GL_FLOAT, 0, 3);
// Draw cube geometry using indices from VBO 1
glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);
glDrawElements(GL_TRIANGLES, gUseGeom.gSize() * 3, GL_UNSIGNED_SHORT, nullptr);
}
存储几何.h
#ifndef STOREDGEOMETRY_H
#define STOREDGEOMETRY_H
#include "geometryengine.h"
class storedGeometry
{
private:
std::vector<GeometryEngine::facetData> useGeom;
std::vector<std::vector<GLushort>> useInd;
std::vector<GLushort> genInd;
public:
// Constructor/Destructor
storedGeometry();
~storedGeometry();
// Setters
void setGeom(std::vector<GeometryEngine::facetData> inGeom);
void addFacet(GeometryEngine::facetData inFacet);
void setIndices(std::vector<std::vector<GLushort>> inInd);
void addIndices(std::vector<GLushort> inInd);
// Getters
std::vector<GeometryEngine::facetData> getGeom();
GeometryEngine::facetData getFacet(int pos);
int gSize();
int iSize();
std::vector<std::vector<GLushort>> getUseIndices();
std::vector<GLushort> getGenIndices();
std::vector<GLushort> getInd(int pos);
};
extern storedGeometry gUseGeom;
#endif // STOREDGEOMETRY_H
存储几何.cpp
#include "storedGeometry.h"
// Constructor
storedGeometry::storedGeometry()
{
std::vector<GeometryEngine::facetData> useGeom;
std::vector<GLushort> useInd;
std::vector<GLushort> genInd;
}
// Destructor
storedGeometry::~storedGeometry()
{
useGeom.clear();
useInd.clear();
genInd.clear();
}
// Setters
void storedGeometry::setGeom(std::vector<GeometryEngine::facetData> inGeom) {
useGeom = inGeom;
}
void storedGeometry::addFacet(GeometryEngine::facetData inFacet) {
useGeom.push_back(inFacet);
// also want to generate indices to go with this at the same time
// can take in indices from rkviz, but are not useful for this purpose
if (genInd.empty()) {
// case 1 - currently no indices, add 0, 1, 2
genInd.push_back(0);
genInd.push_back(1);
genInd.push_back(2);
} else {
// case 2 - already has indices, add n+1, n+1, n+2, n+3, n+3, where n is previous entry
GLushort tInd = genInd[genInd.size()-1];
genInd.push_back(tInd+1);
genInd.push_back(tInd+2);
genInd.push_back(tInd+3);
}
}
void storedGeometry::setIndices(std::vector<std::vector<GLushort>> inInd) {
useInd = inInd;
}
void storedGeometry::addIndices(std::vector<GLushort> inInd) {
useInd.push_back(inInd);
}
// Getters
std::vector<GeometryEngine::facetData> storedGeometry::getGeom() {
return useGeom;
}
GeometryEngine::facetData storedGeometry::getFacet(int pos) {
if (pos <= useGeom.size()) {
return useGeom[pos];
} else {
return useGeom[useGeom.size()];
}
}
int storedGeometry::gSize() {
return useGeom.size();
}
int storedGeometry::iSize() {
return useInd.size();
}
std::vector<std::vector<GLushort>> storedGeometry::getUseIndices() {
return useInd;
}
std::vector<GLushort> storedGeometry::getGenIndices() {
return genInd;
}
std::vector<GLushort> storedGeometry::getInd(int pos) {
if (pos <= useInd.size()) {
return useInd[pos];
} else {
return useInd[useInd.size()];
}
}
storedGeometry gUseGeom;
对于 GUI,不要为它们使用QOpenGLWidget
。 如果你这样做,它会自动在 OpenGL 东西之上呈现 GUI。 为了解决这个问题,添加一个包装器 class 扩展 QMainWindow 以放置 MainWidget 和 GUI。
对于线框,请尝试在调用glDrawElements
之前放置此代码:
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
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