Draw many of the same object quickly in OpenGL

Question

So I\'m working on a game and I need to draw a lot of the same object. Same shape, same size, same color, just different locations.

Right now my setup is like this.

Answer 1

On ~modern hardware, instancing is the way to go.

The idea is that you send the geometry to your GPU once (one draw call), specifying how many instances you want to draw (primCount parameter).

Then in the vertex shader you can use the intrinsic input variable gl_InstanceID to learn which instance is being rendered and then use the appropriate transformation for it. This approach implies that you should have the transformations for all your instances available in the vertex shader, for example in an Uniform Buffer Object.

Edit: The glVertexAttribDivisor function is very useful together with instancing; it basically allows to have some per-vertex attributes together with some per-instance attributes.

Answer 2

There's beautiful thing in OpenGL, called Display list. NeHe production has tutorial on them which should provide all necessary info and examples. But basically:

GLuint displayList; // This should be class attribute
displayList = glGenLists(1);    
glNewList(displayList,GL_COMPILE);
Renderer::draw();
glEndList();

And in real draw method just:

glCallList( displayList);

Don't forget to actualize precompiled display list each time you add/remove something.