What is a simple way to increase distanced to the far clipping plane in OpenGL?

Question

I'm trying to set the far clipping plane to a higher value, but I'm a bit lost.

I'm looking at a complex object using a QMatrix4x4 camera persepective like that:

glMatrixMode(GL_MODELVIEW);
m_view = QMatrix4x4();
m_view.lookAt(QVector3D(17.f, 36.f, 36.f),  // eye
              QVector3D(17.f,  0.f, 19.f),  // center
              QVector3D( 0.f,  0.f, -1.f)); // up
glLoadMatrixf(m_view.data());

Now, looking from this perspective, my object is being clipped by the far plane.

I've tried to increase the far plane distance by using a frustum matrix operation with a huge value. All I want is to modify the back clipping plane:

m_view.frustum(1.f, 1.f, 1.f, 1.f, 1.f, 200000.f);

But this does not show any difference, modifying the farPlane parameter does not change anything. The same applies to ortho:

m_view.ortho(1.f, 1.f, 1.f, 1.f, 1.f, 200000.f);

Or perspective:

m_view.perspective(0.f, 1.f, 1.f, 200000.f);

What's wrong with my approach? How to modify the far clipping plane?

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Edit

I've extended the code snippets above as the problem was not visible. Obviously my mistake was modifying the GL_MODELVIEW instead of the GL_PROJECTION.

Working code should look like that:

// Projection
m_projection = QMatrix4x4();
m_projection.perspective(20.f, m_width / m_height, 0.01f, 2000.f); // note the far plane
glMatrixMode(GL_PROJECTION);
glLoadMatrixf(m_projection.data());
// Model view
m_view = QMatrix4x4();
m_view.lookAt(QVector3D(17.f, 36.f, 36.f),  // eye
              QVector3D(17.f,  0.f, 19.f),  // center
              QVector3D( 0.f,  0.f, -1.f)); // up
glMatrixMode(GL_MODELVIEW);
glLoadMatrixf(m_view.data());

Answer 1

2 issues:

1. You are mixing modelview (lookat) and projection (frustum) operations on the same matrix. You need 2 different matrices.

2. You define the left and right values as both 1.f in ::frustum(). It cannot work, they need to be different. Same for the top and bottom values.

Here is an extract of the definition of QMatrix4x4::frustum():

if (left == right || bottom == top || nearPlane == farPlane)    
    return *this;

So your call to frustum does not do anything.

Once you have good values for top/left/top/bottom, try playing with the near plane distance too, as it might be it that clips your object and not the far plane.