[Solved]How to render text in Qt3D ?

[zol_caonima_zol]

I use renderText() in the QGLView to render a text, but it does not work.

Any ideas to slove these issues for me ? Great Thanks !!!

The core code:
void Geotech::QGLText::draw(QGLPainter *painter)
{
if (_str.isEmpty()) return;

QFontMetrics fm(_font);
QRect rect = fm.boundingRect(_str);  // text bounding box
rect.adjust(0, 0, 1, 1);

QImage image(rect.size(), QImage::Format_ARGB32);
image.fill(0);  // set to transparent

// draw the text on an image
QPainter p2d(&image);
p2d.setFont(_font);
p2d.setPen(QColor(_red * 255, _green * 255, _blue * 255, _alpha * 255));
p2d.drawText(0, 0, rect.width(), rect.height(), Qt::AlignCenter, _str);
p2d.end();

// convert the object coordinate to screen coordinate
GLdouble winx, winy, winz;
QMatrix4x4 model = painter->modelViewMatrix().top();
QMatrix4x4 proj = painter->projectionMatrix().top();
QGLUtils::objectToWindowCoord(_x, _y, _z, model.data(),
                                                     proj.data(), &winx, &winy, &winz);
winy -= rect.height()/2.0;  // align center of height

int x = (int)winx, y = (int)winy;
QVector2DArray vertices;
vertices.append(x, y + rect.height());
vertices.append(x, y);
vertices.append(x + rect.width(), y);
vertices.append(x + rect.width(), y + rect.height());

// texture coordinates
QVector2DArray texCoord;
texCoord.append(0.0f, 0.0f);
texCoord.append(0.0f, 1.0f);
texCoord.append(1.0f, 1.0f);
texCoord.append(1.0f, 0.0f);

// map the image to texture
QGLTexture2D texture;
texture.setImage(image);

// get viewport
GLint view[4];
glGetIntegerv(GL_VIEWPORT, &view[0]);

painter->modelViewMatrix().push();
painter->modelViewMatrix().setToIdentity();

QMatrix4x4 projm;
projm.ortho(view[0], view[2], view[3], view[1], 0, 1);
painter->projectionMatrix().push();
painter->projectionMatrix() = projm;

// move to the actual position from the screen origin
painter->modelViewMatrix().translate(0, 0, -winz);

// enable blend to make the background transaprecy of the text
glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
painter->clearAttributes();
painter->setStandardEffect(QGL::FlatReplaceTexture2D);
texture.bind();
painter->setVertexAttribute(QGL::Position, vertices);
painter->setVertexAttribute(QGL::TextureCoord0, texCoord);
painter->draw(QGL::TriangleFan, 4);
painter->setStandardEffect(QGL::FlatColor);
glBindTexture(GL_TEXTURE_2D, 0);
glDisable(GL_BLEND);

painter->projectionMatrix().pop();
painter->modelViewMatrix().pop();

}