QPaintedTextureImage in Qt3D (Qt 5.8)

本文关键字：Qt in Qt3D QPaintedTextureImage 更新时间：2023-10-16

我想用Qt3D创建一个实体，该实体将自定义图像作为纹理。我遇到了QPaintedTextureImage(链接指向Qt 5.9版本以获取详细信息。这里是 5.8 的文档(，可以用 QPainter 编写，但我不明白怎么写。首先，这就是我想象的实体的样子：

[编辑]：代码已编辑并立即工作！

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 paint 函数的子类化 QPaintedTextureImage：

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

传递给 paint 函数的 QPainter 在 paint 的实现中需要做什么，如果我只想在平面实体上画一个大圆圈？

[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);
}

简短

的回答是...以与平常完全相同的方式使用QPainter。

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。请改用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被覆盖的paint方法。

在 QML 中动态加载所需的图像可能更简单。不久前我不得不这样做，并为此在SO上提出了一个问题：

Qt3D动态纹理