Multiply current Matrix with the stacked Matrix

OpenGL OpenGL: Basic Coding
1

Hi there is there anyway to multiply your current matrix with the one on the stack?

I’m testing out some object oriented coding with multiple cameras
So I have created a 3D world system
every object in it have global positions but local rotations
but to rotate every object locally before i draw them i have to first load an identity matrix then rotate then move it and then

somehow apply it with the camera-matrix that was pushed on the stack. I guess i could make every object store a local rotation matrix and multiply it with the camera-matrix or i hoped that opengl was smart enought to make a built in “multiply current matrix with top stacked matrix operation”, because this probly would be super efficiant rather than storing matrixes some other place.

so is there one?


glPushMatrix(); //push camera matrix on stack
    
    glLoadIdentity();               //creation of object matrix starts here
    glRotatef(rx,1.0f,0.0f,0.0f);   //apply local rotations
    glRotatef(ry,0.0f,1.0f,0.0f);  
    glRotatef(rz,0.0f,0.0f,1.0f);
    
    //space for my hoped matrix operation //merge camera matrix with object matrix
    
    glTranslatef(px,py,pz);         //apply global position
    
    glBegin(GL_LINES);
        glColor4f(1.0f,0.0f,0.0f,alpha);
        glVertex4f(+scale,0.0f,0.0f,alpha);
        glVertex4f(0.0f,0.0f,0.0f,alpha);

        glColor4f(0.0f,1.0f,0.0f,alpha);
        glVertex4f(0.0f,+scale,0.0f,alpha);
        glVertex4f(0.0f,0.0f,0.0f,alpha);

        glColor4f(0.0f,0.0f,1.0f,alpha);
        glVertex4f(0.0f,0.0f,+scale,alpha);
        glVertex4f(0.0f,0.0f,0.0f,alpha);
    glEnd();

glPopMatrix(); //pop camera matrix on the stack
2

Yes, there is glMultMatrixf.
Personally, I suggest that you don’t use these things as they are considered deprecated. Do your own matrix math or use a ready made library. Here is mine
http://www.geocities.com/vmelkon/glhlibrary.html

and some examples here
http://www.geocities.com/vmelkon/gl3_and_glh.html

3

No i dont understand how do you get/use the pushed matrix without using popmatrix? glMultMatrixf( PushedMatrix? )

4

If you want to get the matrix,
float mymatrix[16];
glGetFloatv(GL_MODELVIEW_MATRIX, mymatrix);

If you want to know how to use push and pop

glPushMatrix();
glMultMatrixf(…);
DrawObject();
glPopMatrix(); //for every push, there must be a pop

5

Alright so what you are saying is that my function that i’d like to exist doesnt exist. gotcha.