Текущая modelview матрица.
Assigning to this variable is equivalent to glLoadMatrix(mat) in OpenGL; in other
graphics APIs the corresponding functionality is emulated.
Changing modelview matrix overrides current camera's view parameters, so most
often you want to save and restore matrix using GL.PushMatrix and GL.PopMatrix.
Считывание этой переменной возвращает текущую modelview матрицу.