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Scene partition, Doom3/Quake4

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I was wondering, any one knows what kind of scene partitions algorithm is used by DoomIII / Quake4 ?, just done playing those games, and as usually I’m quite amazed by the amount of effects these games put on the GPU without any visible performance hit so to speak .. I know of the Octree, BSP, algorithms, but when you think of the scenes in DoomIII/Quake4, it seems like the player is always running from one 'room' to another 'room', hence I think they use an algorithm based on rooms and gates, such that the shaders only gets applied on primes in each room. Anyone knows how they do it ?

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As I understand it, that's more or less how they do it. They have portals (in places like doors), then they do software polygon clipping to see if a portal is visible through the other portals between the player and the portal being tested. If it is, what's on the far side is rendered. It's a bit more complicated for lights but I think that's roughly how it works.

As for Doom 3, I just got it, and I'm not impressed. I have a 2GHz P4 and GeForce FX - hardly bleeding edge, but Doom 3 isn't even playable with every graphical setting I can find turned as low as it will go. Far Cry has a much better engine IMHO.

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Original post by ZQJ
As for Doom 3, I just got it, and I'm not impressed. I have a 2GHz P4 and GeForce FX - hardly bleeding edge, but Doom 3 isn't even playable with every graphical setting I can find turned as low as it will go. Far Cry has a much better engine IMHO.

FarCry has a lot of outdoor places, where lightmaps are applied. Only some buildings have real dynamic lightning and shadows. In contrary, everything in Doom3 is dynamic. In the end, you cannot compare both.


Doom3/Quake4 use both a portal culling mechanism, described e.g. here.

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I just wanted to drop in and confirm that Quake 4 and Doom 3 derived games do rely heavily on portal culling for visibility determination. And the CryEngine looks great and performs well but comparing it to Doom 3 is rather pointless as Enrico previously stated.

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Well, Farcry runs like absolute crap on my system (P4 2.8Ghz, nVidia 6800 256MB, 1 gig of RAM). It's slow, and there's graphical bugs everywhere. BF2, Call of Duty 2, and FEAR run just great.

I don't know why, maybe it's some sort of conflict with my hardware?

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So FarCry "cheats" outdoors with lightmaps (etc..) ??

I have to admit, FarCry is without a doubt my favourite 'graphics engine' of the last couple of years. I've argued it before, but HL2 will gather dust on the shelf long before FarCry [smile]

Regardless of the technology, my understanding is that the Doom3 engine (and most of Carmacks other work) has been specifically designed for "indoor" gaming) where the draw distance is relatively limited (or simulated with cheap effects). With that in mind, something like FarCry can't be used as a comparison because it's mostly outdoor - where you have to compensate for huge draw distances etc..

Jack

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Original post by jollyjeffers
I have to admit, FarCry is without a doubt my favourite 'graphics engine' of the last couple of years. I've argued it before, but HL2 will gather dust on the shelf long before FarCry [smile]
With the disclaimer that I haven't patched my game, I was amazed that Far Cry doesn't bother to do even a simple alpha blend fade between it's LoDs, which leads to significant popping in many cases.

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Original post by Promit
With the disclaimer that I haven't patched my game, I was amazed that Far Cry doesn't bother to do even a simple alpha blend fade between it's LoDs, which leads to significant popping in many cases.


Do the other games even have any LOD?

EDIT: Not to mention far cry is significantly older than doom3 and FEAR.

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Quote:
Original post by Enrico
Quote:
Original post by ZQJ
As for Doom 3, I just got it, and I'm not impressed. I have a 2GHz P4 and GeForce FX - hardly bleeding edge, but Doom 3 isn't even playable with every graphical setting I can find turned as low as it will go. Far Cry has a much better engine IMHO.

FarCry has a lot of outdoor places, where lightmaps are applied. Only some buildings have real dynamic lightning and shadows. In contrary, everything in Doom3 is dynamic. In the end, you cannot compare both.


Doom3/Quake4 use both a portal culling mechanism, described e.g. here.

Er, I don't know about the PC version but the XBox version of Far Cry seemed to be mostly shadowmapping, not lightmaps, for the outdoor areas.

But yes, totally different engine tech for totally different environment/focus.

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Thanks Anthony Paul (Sages) for your reply, finally a post from the people behind the real stuff, just what I was hoping for :). I really enjoyed the Quake4 game, damn nice work ...

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