Method renderCameraIndicator

app/src/UI/Widgets/Plot3D.cpp:961–1033

* @brief Renders the camera orientation indicator as a 2D pixmap. */

 * @brief Renders the camera orientation indicator as a 2D pixmap.
 */
QImage Widgets::Plot3D::renderCameraIndicator(const QMatrix4x4& matrix)
{
  struct Axis {
    QVector3D dir;
    QColor color;
    QString label;
  };

  struct TransformedAxis {
    Axis axis;
    QVector4D transformed;
  };

  QImage img(widgetSize(), QImage::Format_ARGB32_Premultiplied);
  img.setDevicePixelRatio(qApp->devicePixelRatio());
  img.fill(Qt::transparent);

  if (width() < 240 || height() < 240)
    return img;

  QPainter painter(&img);
  painter.setRenderHint(QPainter::Antialiasing, true);

  const float lineScale  = 18;
  const float axisLength = 2;
  const QPointF origin(50, 50);

  QVector<Axis> axes = {
    {{1, 0, 0}, m_xAxisColor, QStringLiteral("X")},
    {{0, 1, 0}, m_yAxisColor, QStringLiteral("Y")},
    {{0, 0, 1}, m_zAxisColor, QStringLiteral("Z")}
  };

  QVector<TransformedAxis> transformedAxes;
  for (const auto& ax : axes) {
    QVector4D t = matrix * QVector4D(ax.dir * axisLength, 1.0f);
    transformedAxes.append({ax, t});
  }

  std::sort(transformedAxes.begin(),
            transformedAxes.end(),
            [](const TransformedAxis& a, const TransformedAxis& b) {
              return a.transformed.z() < b.transformed.z();
            });

  painter.setFont(Misc::CommonFonts::instance().customMonoFont(0.8));
  QFontMetrics fm(painter.font());
  int textWidth      = fm.horizontalAdvance("X");
  int textHeight     = fm.height();
  float circleRadius = std::max(textWidth, textHeight) * 0.7f;

  for (const auto& ta : transformedAxes) {
    const QVector4D& t = ta.transformed;
    const float invW   = t.w() != 0.0f ? 1.0f / t.w() : 0.0f;
    QPointF endpoint(origin.x() + (t.x() * invW) * lineScale,
                     origin.y() - (t.y() * invW) * lineScale);

    painter.setPen(QPen(ta.axis.color, 3));