Thread: Some qns to Bubba on MTW terrain engine

Dear Gurus, hi!

I have been going through your posts on game programming (especially the ones related to terrain generation) and thank you very much for your patience in explaining stuff. It is heartening to see people with hard core experience and knowledge spend n number of hours trying to explain the dark arts to the neophytes.

I was wondering if you could comment a bit on the technicalities of the Medieval Total War terrain engine?

*Quad tree or BSP based?

*How come the terrain is so smooth with gentle undulations?

*What is the field of view that they have used do you think?

*How in the wide world did they manage to render 10000+ sprites at the same time and still have MIPS to run their AI?

Thanks in advance.

Best Regards
Fred

Well since this is in the open forum, I can answer one of them

> How in the wide world did they manage to render 10000+ sprites at the same time and still have MIPS to run their AI?
Most likely the AI is on the CPU, and rendering is on the GPU.

It's nothing too amazing, CPUs are VERY fast in comparison how fast to how your eyes work or how fast you can process things.

You still need a video card of some sort*, where do you think those images are sent from? Sure the "card" may be built-in to the motherboard, it's really the same thing.

* It may even be external that converts signals from a USB wire to RCA for example.

I think that's the point or rather the joke that jwenting was making

I was wondering if you could comment a bit on the technicalities of the Medieval Total War terrain engine?

I did not work on the terrain engine and as such anything I might say would be a guess. From what I can see it is either static mesh that the video hardware culls or it uses a quad tree with patches. The terrain on that game is not very complex and it appears they are using texture patches to texture specific patches of terrain. Other engines use this paradigm as well.

*Quad tree or BSP based?

Terrains lend themselves much better to quad trees than BSP. On that merit alone if they are using a tree it is certainly a quad tree.

*How come the terrain is so smooth with gentle undulations?

Bilinear interpolated terrain and/or bilinear interpolated height maps for the terrain data. The terrain does not have sharp transitions such as cliffs and so forth and is most likely using a rather small cell size which translates to an ability to model very smooth hills. Games that have large cell sizes usually have less smooth terrain. However you can create dynamic patches of terrain to smooth out areas and you can use an LOD scheme through quadtrees or something like geo-mip mapping to get smooth detailed terrain up close and less detailed less smooth terrain far away.

*What is the field of view that they have used do you think?

Having played the game a lot and looking at the FOV compared to what I'm used to they are probably using a 75 to 85 degree HFOV. It is not 90 b/c it does not fish eye and distort at the edges of the screen but it is wide so I would say 75 to 80 degrees is about the widest you can get without having some time of fish eye effect.

*How in the wide world did they manage to render 10000+ sprites at the same time and still have MIPS to run their AI?

The first Medieval War cheats and uses 2 triangles per sprite to render all of the combatants. If you look closely you will see them transition from walking north to walking northwest. They hide the fact that there are probably only 8 directions by allowing one 'direction' to cover about 30 to 60 degrees before they render a different direction sprite.

Medieval is not so special as it's sequels Rome: Total War and Medieval 2. These are using true 3D meshes for every object on screen (except for smoke and special effects). This is an accomplishment and all I can say is they are using a clever object and scene manager with a very clever LOD scheme in order to pull it off. It's quite amazing.


However as I said I was not on the dev team and can only comment from what is usually common practice for the genre and from my personal experience of what has worked and what definitely does not work. As a side note on an open forum it is not a good idea to directly address a member in the title of your post. All who frequent this board are knowledgeable enough to answer your questions.