Qt3D 中的 QPaintedTextureImage (Qt 5.8)

Question

我想用 Qt3D 创建一个以自定义图像作为纹理的实体。我遇到了 QPaintedTextureImage (link leads to Qt 5.9 version for details. Here ist doc for 5.8)，它可以用 QPainter 编写，但我不明白如何。首先，这就是我想象中实体的样子：

[编辑]：代码已编辑，现在可以使用了！

planeEntity = new Qt3DCore::QEntity(rootEntity);

planeMesh = new Qt3DExtras::QPlaneMesh;
planeMesh->setWidth(2);
planeMesh->setHeight(2);

image = new TextureImage; //see below
image->setSize(QSize(100,100));
painter = new QPainter; 
image->paint(painter)  

planeMaterial = new Qt3DExtras::QDiffuseMapMaterial; 
planeMaterial->diffuse()->addTextureImage(image);

planeEntity->addComponent(planeMesh);
planeEntity->addComponent(planeMaterial);

TextureImage 是具有绘画功能的 QPaintedTextureImage 的子类：

class TextureImage : public Qt3DRender::QPaintedTextureImage
{
public:    
    void paint(QPainter* painter);
};

传给paint函数的QPainter，如果我只想给planeEntity画一个大圆圈，paint的实现需要做什么？

[编辑] 实现：

void TextureImage::paint(QPainter* painter)
{ 
  //hardcoded values because there was no device()->width/heigth
  painter->fillRect(0, 0, 100, 100, QColor(255, 255, 255));

  /* Set pen and brush to whatever you want. */
  painter->setPen(QPen(QBrush(QColor(255, 0, 255)) ,10));
  painter->setBrush(QColor(0, 0, 255));

  /*
   * Draw a circle (or an ellipse -- the outcome depends very much on
   * the aspect ratio of the bounding rectangle amongst other things).
   */
  painter->drawEllipse(0, 0, 100, 100);
}

Answer 1

简短的回答是...使用 QPainter 与您通常使用的方式完全相同。

void TextureImage::paint (QPainter* painter)
{
  int w = painter->device()->width();
  int h = painter->device()->height();

  /* Clear to white. */
  painter->fillRect(0, 0, w, h, QColor(255, 255, 255));

  /* Set pen and brush to whatever you want. */
  painter->setPen(QPen(QBrush(QColor(0, 0, 0)) ,10));
  painter->setBrush(QColor(0, 0, 255));

  /*
   * Draw a circle (or an ellipse -- the outcome depends very much on
   * the aspect ratio of the bounding rectangle amongst other things).
   */
  painter->drawEllipse(0, 0, w, h);
}

但是请注意，您确实不应该直接调用 paint 方法。而是使用 update 这将导致 Qt 安排重绘，初始化 QPainter 并使用指向该画家的指针调用重写的 paint 方法。

Answer 2

在 QML 中动态加载您需要的图像可能会更简单。不久前我不得不这样做并为此打开了一个问题：

Qt3D 中的 QPaintedTextureImage (Qt 5.8)

QPaintedTextureImage in Qt3D (Qt 5.8)

c++

qt

qt3d