Is in QtOpenGL gluUnProject

glararan

Hi,

As topic say I'm asking for gluUnProject function for OpenGL. I can't found it in 4_0 Core and I can't found it in newest release.

Is this function just in basic OpenGL or is implented in Qt?

ZapB

Indeed. With modern OpenGL you are responsible for managing matrices. Luckily Qt provides QMatrix4x4 which you can use to construct a projection matrix and it's inverse.

glararan

Ok, my camera is based on QMatrix4x4.

Im using in camera these properties:
viewMatrix, projectionMatrix and viewProjectionMatrix

I tried to figure it out with this code:
@ QMatrix4x4 inverted = m_camera->projectionMatrix() * m_camera->viewMatrix();
inverted = inverted.inverted();

    float posZ;

    m_funcs->glReadPixels(mouse_position.x(), mouse_position.y(), 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &posZ);

    QVector4D clickedPointOnScreen(mouse_position.x(), mouse_position.y(), posZ, 1.0f);
    QVector4D clickedPointIn3DOrgn = inverted * clickedPointOnScreen;

    terrain_pos = clickedPointIn3DOrgn.toVector3D();

    qDebug()  << terrain_pos;@

But it returns small values :/
I'm with camera on position: 250.0f, 10.0f, 250.0f
And I'm getting: QVector3D(415.715, 99.3959, 6.45992) (cursor is in center of QGLWidget screen, i calculated coords)

MicPiano

Hi, I know this is kinda old topic. But I will still reply anyway.
I was doing the same thing in the past few days and found out that the near-z of the perspective matrix will affect the result.
Vector3D::unProject() already does the inverting for you.
When you un-project a value from screen coordinates, it automatically changes the coordinates into the near-z plane.
if you #include <GL/glu.h> you will find the mythical gluUnproject() function :)