Saving rotation Matrix in OpenGL - opengl

Question

I'm writing an OpenGl program about a cone rotating in 3D space and I have a txt with datas of the angles and the axes around whom the rotation takes place.
The problem is that OpenGL requires the total rotation angle while in the file I have the increment in angle for every time step.
here my code :
GLdouble matrice1 [] {1.,0,0,0,0,1.,0,0,0,0,1.,0,0,0,0,1.};
GLdouble * matrice = matrice1;
void displayCone(void){
// clear the drawing buffer.
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //
// set matrix mode
glMatrixMode(GL_MODELVIEW);
// clear model view matrix
glLoadIdentity();
//gluLookAt(3.0, 3.0, 3.0-4.5, 0.0, 0.0,-4.5,0,0,1);
gluLookAt(3.0, 3.0, 3.0, 0.0, 0.0,0.0,0,0,1);
glBegin(GL_LINES);
glColor3f (1.0, 0.0, 0.0);
glVertex3f(0.0, 0.0, 0.0);
glVertex3f(2.0, 0.0, 0.0);
glColor3f (0.0, 1.0, 0.0);
glVertex3f(0.0, 0.0, 0.0);
glVertex3f(0.0, 2.0, 0.0);
glColor3f (0.0, 0.0, 1.0);
glVertex3f(0.0, 0.0, 0.0);
glVertex3f(0.0, 0.0, 2.0);
glEnd();
//glLoadMatrixd(matrice);
glColor3f(0.8, 0.2, 0.1);
glMultMatrixd(matrice); // <------ ** me trying to implement the previous rotation before //rotating of the increment angle xRotated
glRotated(xRotated,a1,a2,a3); // <----- **here the rotation**
glGetDoublev(GL_MODELVIEW, matrice); // <----- ** me trying to save the total rotation //matrix **
glTranslatef(0.0, 0.0, height);
glutSolidCone(base,height,slices,stacks);
glPushMatrix();
glTranslatef(0.0, 0.0, height-0.1);
glutSolidCylinder(0.07,height_c,slices,stacks);
glPopMatrix();
glPushMatrix();
glScalef(1.0,1.0,-1.0);
//glTranslatef(0.0, 0.0, 2*height);
//glPopMatrix();
//glPushMatrix();
glutSolidCone(base,height,slices,stacks);
// Flush buffers to screen
glPopMatrix();
glFlush();
}
What I'm trying to do here with glGetDoublevand glMultMatrixdis to save the precedent Rotation Angle but this doesn't work. Does anyone know how to save the precedent rotation matrix in order to get the total rotation and not the RotationAngle of the increment angle ?

Answer 1

For one, that code you have there is using the old and busted fixed function, legacy API that's been out of fashion for well over 15 years.
More to the point, you can use a proper 3D graphics math library (GLM, Eigen, linmath.h) to manage a rotation matrix and apply it to the OpenGL transformation matrix stack using glMultMatrix instead of using multiple calls to glRotate. Or manage the whole transformation matrix yourself and just load it with glLoadMatrix.
And when you do your own matrix management, it's only a small step to ditch the fixed function pipeline and use shaders, where you pass the matrix as so called uniform values.