OpenGL gluPickMatrix not existing

[sandro4912]

OK i could install it. But what else do i have to do that the project finds it?

[SGaist]

Taking a look at the package content, the header is under "GL/glu.h".

[sandro4912]

I added the header however its not found.

Steps i took:

sudo apt-get update
sudo apt-get install libglu1-mesa-dev

Restart the project and

#include "gl/glu.h"

[SGaist]

Casing is important.

[sandro4912]

Ok I changed it to the correct:

"GL/glu.h".

It looks like it is found. However when i compile i still get an error with the gluPickMatrix like this:

../tetrahedron/tetrahedron.cpp:128: undefined reference togluPickMatrix'
`

[SGaist]

You need to also link to libGLU.

[wrosecrans]

GLU was last updated in the 1990's, it's basically deprecated, and depends on functionality that was deprecated from OpenGL years ago. Ideally you should find a different way of doing what you are trying to accomplish. If you are using any kind of modern OpenGL with vertex shaders from the last ~15 - 20 years, GLU will have no idea how to understand your projection matrices, and the results it gives you will be nonsensical or wrong even if you get it working.

[sandro4912]

The whole code which uses the gluPickMatrix looks like this.

int Tetrahedron::faceAtPosition(const QPoint &pos)
{
    constexpr int MaxSize = 512;
    GLuint buffer[MaxSize];
    GLint viewport[4];

    makeCurrent();

    glGetIntegerv(GL_VIEWPORT, viewport);
    glSelectBuffer(MaxSize, buffer);
    glRenderMode(GL_SELECT);

    glInitNames();
    glPushName(0);

    glMatrixMode(GL_PROJECTION);
    glPushMatrix();
    glLoadIdentity();
    gluPickMatrix(GLdouble(pos.x()), GLdouble(viewport[3] - pos.y()),
                  5.0, 5.0, viewport);
    GLdouble x = GLdouble(width()) / height();
    glFrustum(-x, x, -1.0, 1.0, 4.0, 15.0);
    draw();
    glMatrixMode(GL_PROJECTION);
    glPopMatrix();

    if (!glRenderMode(GL_RENDER)) {
        return -1;
    }
    return static_cast<int>(buffer[3]);
}

What would be an alternative?

And how can i link against libGLU?

[jsulm]

@sandro4912 said in OpenGL gluPickMatrix not existing:

And how can i link against libGLU?
Add

LIBS += -lGLU

to your pro file.

[sandro4912]

The linking worked.

However i found this approach to implement gluPickMatrix and not need the glu library:

void gluPickMatrix(
        GLdouble x, GLdouble y, GLdouble deltax, GLdouble deltay,
        GLint viewport[4])
{
   if (deltax <= 0 || deltay <= 0) {
       return;
     }

   /* Translate and scale the picked region to the entire window */
   glTranslated((viewport[2] - 2 * (x - viewport[0])) / deltax,
           (viewport[3] - 2 * (y - viewport[1])) / deltay, 0);
   glScaled(viewport[2] / deltax, viewport[3] / deltay, 1.0);
}