Mod-making limitations and more light questions.

So far I've come to understand that making a mod involves changing anything but the actual rendering code. With that in mind, I've been watching the progress of the Quake 3 Fortress mod, and they've been adding all sorts of things to it like panel entities, enhanced particle effects, lens flares, etc., all of which sounds like could be added without messing with the rendering portion of the game. What gets me is how they can add new entities. I'm aware that currently, making entities involves assigning entity attributes to a piece of geometry(door, elevator, switch, whatever), and making point entities, like light and sound sources.

Well, I read somewhere by Zaldron that it may be very well possible that this way of doing "entities" won't exist in the new Doom. More like "controllers", like he calls them. So, my question is, just how easy would it be to add in controllers? And since in the past lights were entities, will they fall under the controllers category?

Secondly, about the particle system. Since this is the first engine with uniform real-time lighting, and if you were using the particle system to simulate fire, or some other effect that produces light, just how would the engine handle the lighting for that? I haven't seen the QuakeCon video scene with the demon in the fire in a long time, so I don't remember how the lighting looked.

Lastly - for Zaldron. You can't be here every waking moment when I might think up a brand new question, and as much as you know, some things you won't be able to answer, so I'm wondering if you would be so generous to provide links to websites that talk about real time 3D engines in-depth, as well as ones that talk about the other parts of the game's infrastructure, like the AI, and stuff. Thanks.

So far I've come to understand that making a mod involves changing anything but the actual rendering code.

Well, the core engine is much more than the rendering code alone. There's the networking, sound, game logic, physics etc.

I haven't seen the QuakeCon video scene with the demon in the fire in a long time, so I don't remember how the lighting looked.

It looked pretty damn good. I don't know how the lighting is done there - maybe you have to put in some flickering point lights automatically, or the engine does it for you. Or maybe the light sprites just have a light-emitting shader of some kind.

Adding new entities is a bit tricky because it affects the way the tools compile the map. I suppose they're using a modified version of the Q3BSP tools. Entities aren't that hard to add, it's an addition to the game source and it could be as simple as adding new controls on the menu, up to reworking entirely the way brushes are handled.

About the particle systems. A particle system is basically a fucking complex algorythm (or a very simple where you can plug in extra behaviors) where you calculate the position, duration and private properties of a bunch of 3D coordinates. This coords are used to display a decal (like fire, smoke, sparks and the like) or real polygons (rocks, debris, shotgun pellets, metal shreds, etc). I suppose the Doom engine will be able to properly cast shadows over and from polygon-based particles, but what about the decals like the ones used in the fire?

I suppose they do exactly what Flathead says, they place a couple of point lights, supposedly one per focus, and link it with a special "flickering" shader, that would pretty much look like a noisy pattern that moves very erraticly.

This is kinda hard to do right, though, so maybe id is doing something different. You can't project a rectangular image using a spherical enviroment mapping whitout producing singularities. OK that doesn't make any sense. What I mean is that the texture, doesn't matter if it tiles several times or not, is casted from that single point to all directions, much like an everexpanding sphere that engulfs the world polygons. Since there is no proper way to texture a sphere without making at least one point where all the pixels stretch and meet in a very ugly fashion, that lighting could look very crappy.

Oh, and about the sites. Hell I have no idea. Gamasutra is a good place but they don't ussually cover the kind of topics you're looking for.

What I know is the end product of messing around with MAX, playing games, modding games and even trying to create one.

Also, what about doing lightning? I have no idea how this would be handled, and with the real-time lighting, would it act like it does in real life?

Lightning? That's an extensive light souce, and would need some pretty complex lighting solutions to make it right. They'll probably just put one very intense lightpoint on the focus, and maybe one on the target.

The nearly-erratic behavior of lightning bolts have absolutely nothing in common with raycasting.

Lightning? Why not just make the screen go white for a few moments :)

I take it that they're talikin' about lighting as opposed to lightning.
Am I right?

No :P

No, he said lightning, like the bolts.

Oh, sorry.
Apparently, I can't read.