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Main OpenGL Matrices

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Three main OpenGL matrices are: GL_PROJECTION (projection matrix), GL_MODELVIEW (modelview matrix) and GL_VIEWPORT (viewport matrix). Although the last one isn't really a matrix, rather a vector (array) of four elements.

Projection matrix defines how big is the angle of view, what is the aspect ratio and clipping ranges.

Modelview matrix defines where the camera is and where the object is (oversimplification).

Viewport matrix defines range screen space coordinates, except for z coordinate.

PyOpenGL

Getting those:

view = glGetInteger(GL_VIEWPORT)

proj = glGetDoublev(GL_PROJECTION_MATRIX)

model = glGetDoublev(GL_MODELVIEW_MATRIX)

Setting those:

glViewport(*view)

glMatrixMode(GL_PROJECTION)
glLoadMatrixd(proj)

glMatrixMode(GL_MODELVIEW)
glLoadMatrixd(model) 

C++

Getting those:

GLdouble buffer[16];
glGetDoublev(GL_PROJECTION_MATRIX, buffer);

GLdouble buffer[16];
glGetDoublev(GL_MODELVIEW_MATRIX, buffer);

GLuint view[4];
glGetIntegerv(GL_VIEWPORT, buffer);

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