THere is an article recently posted at devmaster.net .. with comparisons about D3 vs Hl2 engine capabilities.. it is Very nice to see developers actually writting articles for gamers. for them to understand a little more the technology behind the games the loves to play. however i disagree with some of his comparisons..
1)Lighting and shadowing..
Hl2 ,neither any other *comercial* real game engine exist that use realtime radiosity ,no game engine support that , and not for many years. what Hl2 use is Static radiosity pre-rendered maps. they use multiple maps to fake lighting and bumping. QUake3 used a simpler technique ,but yes it also use static rediosity maps.. and lightmaps..
i pretty much agree here with him.. when he says you can do big outdoors in D3. both engines support very big outdoors or indoors if you want. you can easily test this by buiding in D3 editor the biggest BOX map you can, and you will notice how big is the area the editor allows you to work. any Stalker or FArcry level easily fits in the Doom3 land. problem with D3 engine outdoors is that it doesnt have out of the box tools for nature creation enviroments.. No water ,no lakes ,forest or whether effects , so Doom3 outdoors will be limited to rocks.., faked grass (painted textures) or hand made trees exported from third party 3d animation software..which there is nothing wrong with the last one ,except that is not very efficient for a game. D3 outdoors capacity are mostly the same as Quake2 and quake3 engines were ,but without the size limitations. Farcry ,Stalker ,Hl2 are superior here because they have many content ,already many tools for terrain and nature creation with Dx9 effects.for example Farcry even have a realtime editor where you can create a Hill ,a tree, grass and modify whatever you wish in a level *while you are playing the game.* amazing if you ask me.
3)characters models..and animation
Here the author go it reversed. Doom3 engine have no competiton here.. none. Hl2 is just polygons and nice looking textures to make their characters looks better.. D3 engine *can use* not only Polygons ,not only nice textures ,but also its powerfull realtime lighting /normal/specular mappingengine to increase the quality of their characters far more. here is where i think where Doom3 is revolutionary . the low poly characters in the game is merely a design decision.. but the technology in the character depertment is superior in every way.. to Hl2.or any other game. Animation ? the mouth animation of Hl2 is good for nothing.. excepth cutscenes ,trailers or tech demos. good for PR marketing .it is too much tech,for so little use in the game . if they dedicated that much effort for the whole character animation .(the entire body) ,not only the mouth. it will be a very diferent story.Hl2 character *body* animations are hand made .. Doom3 contrary to Hl2 use a Mocap .. (motioncapture animation data)where their developers film and use real life people motion for their game. it support and advanced character skeletal animation .you will notice the "real life look" of Doom3 characters animations in many of the cutscenes when there are many soldiers at the same time running . Hl2 characters have the "robotic look" of most Fps games...imho.. there is no bigger dissapoinment (apart from subpart graphics in games) than poor character models and animations. SO what it is important is not which engine support more.. polys.. because probably here the limits of the each engine are quite high.. but which ones allows more eye candy.. and here DOom3 has no competition.. thanks because again it can use not only very high polymodels/textures if you want ,but also its realtime ligting and *EXTRA multi layers of textures* allows a new level of detail that was never possible before.. and still no other released game can match.
4)networking ,AI and Physics..
i pretty much agree there.. Hl2 wins there.. however Havok physics was not made by valve.. so anyone looking to license source engine.. will also need a license the physics engine from Havok. many games already also have licenses..
my conclusion is that each engine is great for the game they were made. Hl2 game will not work in the D3 engine..out of the box. because its outdoors ,Ai and networking limitations. and a D3 game will look good in Hl2 engine because of the its limited dynamic lighting abilities. a D3 level in Hl2 will look terrible .. without realtime lighting/shadows and an outdoor of Hl2 in D3 will look unrealistic without vegetation ,sky,water ..and so on.
Doom3 engine was made just with DOom3 in mind , that is Dark and industrial rusty style enviroments .here its looks perfect .any other enviroments the lighting will look wrong ...either plastic or washsheout . since D3 engine speculars are fixed around Blinn materials.. "only good for metals". and seems that it doesnt do a good job with AMbient lighting .. necessary for very illuminated outdoors.. like Farcry/Hl2. probably the solution here will be lightmaps.
HL2 engine allows far bigger creativity ,since it has less limitations in its engines/tools for Mods .. it have more stuff ,but doesnt have anything that should be called "NEXT GEN" only today stuff. Doom3 in the other hand have less features.. but the ones it have are more or less revolutionary ..like it unified realtime lighting engine ..which it is great for many cool things.
Havok physics are revolutionary ,but that doesnt count as an "Engine feature" since its was licensed from others. one thing to remember is that Quake4 and other games in the "Doom3 engine" will most likely have a very updated Doom3 engine for the needs of their game.. whether by their developers RAVEN or by idsoftware . just like Q3->COD or UT2004->SC3 . So whenever QUake4 or others games are released ,, it will most likely have many upgrades.. to allows more cool stuff ,with better gameplay.