I've coded in lightmapping into my opengl game. Currently all lights are static, so lightmaps for all the surfaces are generated at start up. I intend to use dynamic lighting as well, such as torches, explosions etc. What is the best way of optimising this? If I generate the dynamic lightmaps every frame isn't it likely to slow down the frame rate? Should I keep the static lights and then render another (dynamic) light map on top of it when rendering? It just seems like it could really slow things down

Can you just use the built-in lighting features of opengl for dynamic stuff? Set a point light on the explosion? That'll be a lot faster, certainly, and explosions are usually long enough that shadows are important for effect, at least during gameplay.

If the torches are themselves static, and can just be on or off, you could also make a system for switching lightmaps based on the torch configuration, although with enough torches that could get memory-heavy.

It's things like this why vertex and fragment programs were invented. Feel free to use them.

If you're, for whatever reason, targetting hardware that doesn't provide such features, I wouldn't bother with dynamic lighting. It isn't worth the effort. Just stick to lightmaps and you'll be fine.

I don't know for sure, but that just sounds really slow. Couldn't you do something with vertex normals to get an intensity of the dynamic light color and then use glColor3f() to apply it to the smooth shaded vertex/texture?

Ugh.

These are two fundamentally different ways to think about rendering. One method needs to constantly provoke state-changes, thus destroying performance.

The program method can be done easily enough such that it work with the hardware, not against it.

It's better to have more interesting geometry than to have very basic geometry and lighting.

Yes. The polygon count and texture work is more important than dynamic lighting.

thanks for the feedback on this post. I've been playing around with a few things and probably going to do as suggested and render three layers: the texture layer, static lightmap and then (if necessary) dynamic lightmap to each surface.
I thought you might be interested in how its turned out so I've attached a screenshot
It just shows a light in a corner of a room. The screen dump turned out incredibly dark for some reason. I edited the brightness which is why the colours might seem a bit odd.
I've tried using the opengl lighting before, and found that it generally sucks. I've also tried doing as nonnus suggested by setting an appropriate colour to each vertex of the surface, but this is only effective for small surfaces. for example, if you have a large wall with the light source torwards the middle of the wall, the wall will end up being darker than it should be.

edit: I also attached another screen to the original post

its going to be a while yet, because I started completely re-writing my game. I also have A level exams coming up over the next month so will spend quite a bit of time revising. When I've implemented proper clipping, skeletal animation and rigid body physics I'll probably upload a demo. The skeletal animation / rigid body physics are going to take quite a while. I've done them before though so I know what I'll be doing. Its gonna kick ass to have ragdoll!