scott <sco### [at] scottcom> wrote:
> For a games console it's probably enough.  What do you hold in RAM during a 
> game?  All the 3D meshes and textures are on the GPU video memory only*. 

  That's actually not true.

  In big games typical scenes may consist of hundreds of thousands, if not
even millions of polygons. You *can't* render them all even with the most
modern graphics cards.

  Game engines implement an ample variety of techniques to reduce the amount
of polygons sent to the graphics card. The optimal situation is that only
those polygons which are visible in the current frame are sent to the
graphics card to be rendered.

  Many of these techniques are things which are not supported by graphics
cards but must be calculated by the CPU. These include things like BSP
trees, dividing the scene into sectors, portals, occlusion volumes,
billboard sprites, etc.

  Also in most modern games the scene to be rendered is seldom static,
but changes all the time. For example dynamic shadows, at least if
implemented using shadow volumes, require new shadow polygons to be
created at each frame and sent to the graphics card. Of course in order
to create the shadow polygons in the first place you need the scene
itself (and all of its optimizations) in RAM.

  Games also need to do a whole lot more than that as well. For example
most current games have some kind of physics engine, which requires its
memory. The list is endless.

-- 
                                                          - Warp

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