We always wanted to have crowd scenes in Kameo and started to do some experiments with the Xbox 1 and figured we could get maybe 100 or so NPCs. Once we moved onto the Xbox 360 we thought, "Let's try something that will slow it down, how about 1,000? Ran fine, no problem whatsoever! How about 3,000? Still fine!" Then we thought we had better try it with something more taxing than a test level so we put them on the Battle Field level which was all parallax and normal mapped, had a huge draw distance and lots of special effects like volumetric smoke; it still ran fine. In the released game we had something like 3000-plus NPCs because more than that was hard to choreograph, but the 360 can do much more. At one point during debug we found that each of the NPCs in one scene were being drawn 4 times by mistake, that's 12,000 being drawn and still no sign of slowdown.

We had a similar story with the GPU particle systems... We had a test running with a 100,000 particles being computed purely on the GPU, no CPU intervention at all. Now the Xbox 1 could do that but on the 360 they all react to the player and hit the floor and are lit, then we tried more, lots more! How about 1 milion? We aren't talking test levels or tech demos here. They are actually in the released game, and you can go and count them in the Throne Room. Most levels don't have quite that many though as only about 300,000 are normally in visible range at one time.

When thinking about the NPC and particle rendering, remember to put it into context; these are not tech demos and they represent a tiny amount of the actual graphical load Kameo puts on the Xbox 360. Each scene has hugely complex shaders on the geometry that would not have been possible on previous generation hardware, or even on the PC until recently. Almost every surface in Kameo is both normal and parallax mapped, has a detail map, is shadowed, has some global illumination and has an accurate dynamic lighting model. On top of the main model shaders, you have so many effects such as (but not all) particles, volumetric smoke and fire, instanced foliage, grass shaders, true reflections, accurate depth of field, bloom, color correction, real-time water surfaces, heat haze, and much more.