QMatrix4×4 is transformation matrix in 3D space so you can use it where ever you want.

Immii,

You sound like you have not been working with 3D graphics.

Any qualified answer, please?

Thanks.

NorskQt wrote:

Hi,

I have two simple questions related to QMatrix4×4 :

1. Is this matrix OpenGL compliant? If not, is there an easy way converting it to OpenGL matrix (float array of dimesion 16)?
2. How is this matrix indexed, usual C/C++ notation starting from zero, eg Qmatrix4×4 m(0,0) = refers to the first element in the matrix row : 0 and column : 0)?

Thanks!

Unfortunately, QMatrix4×4 is a matrix of 16 qreals, which may or may not be GL_FLOAT — and usually they are not, since qreal is double everywhere except on ARM, and GL_FLOAT is float everywhere. Qt uses some internal macros to do the job: see for instance
http://qt.gitorious.com/qt/qt/blobs/master/src/opengl/qglshaderprogram.cpp#line2188

Apart from this, internally QMatrix4×4 is a qreal[ 4 ][ 4 ] packed in column-major order (i.e. operator()(x, y) will assign to data[y][x], matching OpenGL), so the first element is indeed (0, 0).

Hi Peppe,

Thank you very much for providing information about QMatrix4×4. It’s a kind of strange though because Qt works with OpenGL and Qt’s 3D-graphics matrix is not OpenGL compliant. This is something that the Qt developers should consider.

Thank you very much again.

Hi there,

correct my if I’m wrong but opengl can be used with floats.
Just use gl…d instead of the gl…f in these case glLoadMatrixd

Greetings,
bbuerger