OpenGL Display Lists

Question

Can someone please explain to me how to modify a display list in OpenGL once its compiled? How can I enforce, for example a matrix transformation on it?

Thanks in advance.

Answer 1

Display lists are immutable; you cannot alter them once created. That's pretty much the point of them.

If you want to have geometry built into a display list that can be rendered at a place defined by a matrix, you simply don't put matrix commands in the display list. Just put the drawing stuff in a display list. When you want to render that geometry, do the setup work (including matrix stuff) and then execute the display list.

Your current code looks something like this:

//Every frame
glRotatef(...);
glTranslatef(...);

///More setup work.

glBegin(...);
glVertex/TexCoord/Color/etc(...);
...
glEnd();

Your display list-based code should look like this:

//Initialization. Done once.
glBeginList(...);
glBegin(...);
glVertex/TexCoord/Color/etc(...);
...
glEnd();
glEndList();

//Every frame
glRotatef(...);
glTranslatef(...);
...

glCallList(...);